<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:d785667b-2bbb-4b67-b881-85b5d8a05376,g:e86a97c1-f64e-401d-84e4-f55e82b0fce5-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.supernus.com/role/CondensedConsolidatedStatementsofEarningsLoss" xlink:type="simple" xlink:href="supn-20240630.xsd#CondensedConsolidatedStatementsofEarningsLoss"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/CondensedConsolidatedStatementsofEarningsLoss" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_48a4d452-a530-4306-8938-edf04ea2d20f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:to="loc_us-gaap_StatementTable_48a4d452-a530-4306-8938-edf04ea2d20f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_94169c86-9db4-4086-b834-ffc668778a24" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_48a4d452-a530-4306-8938-edf04ea2d20f" xlink:to="loc_srt_ProductOrServiceAxis_94169c86-9db4-4086-b834-ffc668778a24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_94169c86-9db4-4086-b834-ffc668778a24_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_94169c86-9db4-4086-b834-ffc668778a24" xlink:to="loc_srt_ProductsAndServicesDomain_94169c86-9db4-4086-b834-ffc668778a24_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_ac0c0987-c777-442b-bfe4-a1be7f121fba" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_94169c86-9db4-4086-b834-ffc668778a24" xlink:to="loc_srt_ProductsAndServicesDomain_ac0c0987-c777-442b-bfe4-a1be7f121fba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_46146060-7fdd-4453-9cf7-7cdc1be281f2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_ac0c0987-c777-442b-bfe4-a1be7f121fba" xlink:to="loc_us-gaap_ProductMember_46146060-7fdd-4453-9cf7-7cdc1be281f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_RoyaltyLicenseAndOtherRevenueMember_517640a3-f0a1-472f-909c-e5dbc69e3868" xlink:href="supn-20240630.xsd#supn_RoyaltyLicenseAndOtherRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_ac0c0987-c777-442b-bfe4-a1be7f121fba" xlink:to="loc_supn_RoyaltyLicenseAndOtherRevenueMember_517640a3-f0a1-472f-909c-e5dbc69e3868" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_8e63052f-19bd-461e-ab2b-ccdc3c4106a8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:to="loc_us-gaap_RevenuesAbstract_8e63052f-19bd-461e-ab2b-ccdc3c4106a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d5eb320b-21e5-41a0-9274-a9832e3c46a7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_8e63052f-19bd-461e-ab2b-ccdc3c4106a8" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d5eb320b-21e5-41a0-9274-a9832e3c46a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_bd781834-00f1-4197-93d7-9f17216127a1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_bd781834-00f1-4197-93d7-9f17216127a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_26470660-e09c-42c8-ad78-f5a4b525e09e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_bd781834-00f1-4197-93d7-9f17216127a1" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_26470660-e09c-42c8-ad78-f5a4b525e09e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_da64338d-0f7b-4b9c-be0a-31c527b52080" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_bd781834-00f1-4197-93d7-9f17216127a1" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_da64338d-0f7b-4b9c-be0a-31c527b52080" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_b88c332f-cc0e-4365-8dd5-3162d34d4087" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_bd781834-00f1-4197-93d7-9f17216127a1" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_b88c332f-cc0e-4365-8dd5-3162d34d4087" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_4fedf1eb-6a74-4e5d-8877-2cdc397a6edd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_bd781834-00f1-4197-93d7-9f17216127a1" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_4fedf1eb-6a74-4e5d-8877-2cdc397a6edd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_1b8190f0-8897-43af-a875-40659217c551" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_bd781834-00f1-4197-93d7-9f17216127a1" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_1b8190f0-8897-43af-a875-40659217c551" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_6684451c-0688-44be-97db-6d697e81b8c1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_bd781834-00f1-4197-93d7-9f17216127a1" xlink:to="loc_us-gaap_CostsAndExpenses_6684451c-0688-44be-97db-6d697e81b8c1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_3e1967be-e849-46e1-9df6-4cf83157b3f4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:to="loc_us-gaap_OperatingIncomeLoss_3e1967be-e849-46e1-9df6-4cf83157b3f4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_75fcf933-3c70-4327-9177-062d295f67b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_75fcf933-3c70-4327-9177-062d295f67b1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_28692284-f43b-479a-b348-e4091cb5b636" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_75fcf933-3c70-4327-9177-062d295f67b1" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_28692284-f43b-479a-b348-e4091cb5b636" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_14214cee-52da-48bb-8765-e51f56ad2f3b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_75fcf933-3c70-4327-9177-062d295f67b1" xlink:to="loc_us-gaap_InterestExpenseNonoperating_14214cee-52da-48bb-8765-e51f56ad2f3b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_3c59f25f-e941-43ff-bc63-8596d1c003b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_75fcf933-3c70-4327-9177-062d295f67b1" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_3c59f25f-e941-43ff-bc63-8596d1c003b1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_e3e8e1a6-46af-4bfe-b053-0f6f64f0d497" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_e3e8e1a6-46af-4bfe-b053-0f6f64f0d497" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_b8845de3-510b-453c-8267-c0f183309a8c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_b8845de3-510b-453c-8267-c0f183309a8c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_5ee84834-7572-424e-9e3e-ff88141dbc3e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:to="loc_us-gaap_NetIncomeLoss_5ee84834-7572-424e-9e3e-ff88141dbc3e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_EPSBasicAndDilutedAbstract_69297444-0595-4037-a4c8-26803c09a350" xlink:href="supn-20240630.xsd#supn_EPSBasicAndDilutedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:to="loc_supn_EPSBasicAndDilutedAbstract_69297444-0595-4037-a4c8-26803c09a350" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_b7db80f7-f72b-41b7-bd5e-4daba009ebd5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_supn_EPSBasicAndDilutedAbstract_69297444-0595-4037-a4c8-26803c09a350" xlink:to="loc_us-gaap_EarningsPerShareBasic_b7db80f7-f72b-41b7-bd5e-4daba009ebd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_0238af99-e7ec-4084-b0bf-7734a8244f82" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_supn_EPSBasicAndDilutedAbstract_69297444-0595-4037-a4c8-26803c09a350" xlink:to="loc_us-gaap_EarningsPerShareDiluted_0238af99-e7ec-4084-b0bf-7734a8244f82" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_b8592c83-6763-44d1-bcac-e4f2e05bf26b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8a3503ef-135c-4866-9479-007411f6013d" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_b8592c83-6763-44d1-bcac-e4f2e05bf26b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_fb146fa7-39d9-4b3c-aae7-6e64cc8a98cd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_b8592c83-6763-44d1-bcac-e4f2e05bf26b" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_fb146fa7-39d9-4b3c-aae7-6e64cc8a98cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_6dc311a7-a142-4be7-9fe1-f20a6edd597d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_b8592c83-6763-44d1-bcac-e4f2e05bf26b" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_6dc311a7-a142-4be7-9fe1-f20a6edd597d" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/CondensedConsolidatedStatementsofChangesinStockholdersEquity" xlink:type="simple" xlink:href="supn-20240630.xsd#CondensedConsolidatedStatementsofChangesinStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/CondensedConsolidatedStatementsofChangesinStockholdersEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_efb7a2c8-e7fd-4896-9889-ee3018853a1e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_438062fd-5a50-42be-8e95-7d57a942b8fe" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_efb7a2c8-e7fd-4896-9889-ee3018853a1e" xlink:to="loc_us-gaap_StatementTable_438062fd-5a50-42be-8e95-7d57a942b8fe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_4f7d814b-0382-41a1-84c8-d17dc6296b93" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_438062fd-5a50-42be-8e95-7d57a942b8fe" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_4f7d814b-0382-41a1-84c8-d17dc6296b93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_4f7d814b-0382-41a1-84c8-d17dc6296b93_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_4f7d814b-0382-41a1-84c8-d17dc6296b93" xlink:to="loc_us-gaap_EquityComponentDomain_4f7d814b-0382-41a1-84c8-d17dc6296b93_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_93de8662-455b-49fa-b882-d29949fbd43a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_4f7d814b-0382-41a1-84c8-d17dc6296b93" xlink:to="loc_us-gaap_EquityComponentDomain_93de8662-455b-49fa-b882-d29949fbd43a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_d8e9f835-70dc-4413-91ce-eb04a9e2e420" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_93de8662-455b-49fa-b882-d29949fbd43a" xlink:to="loc_us-gaap_CommonStockMember_d8e9f835-70dc-4413-91ce-eb04a9e2e420" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_b23bc8e4-2d3e-4b81-a8f6-55b3daf7845b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_93de8662-455b-49fa-b882-d29949fbd43a" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_b23bc8e4-2d3e-4b81-a8f6-55b3daf7845b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_eb12aea9-1108-4f6a-aeda-6c661d1950d9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_93de8662-455b-49fa-b882-d29949fbd43a" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_eb12aea9-1108-4f6a-aeda-6c661d1950d9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_ae225415-eafd-4ef7-b734-494155e5bb6e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_93de8662-455b-49fa-b882-d29949fbd43a" xlink:to="loc_us-gaap_RetainedEarningsMember_ae225415-eafd-4ef7-b734-494155e5bb6e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f0e13be-baa9-4a03-bd67-803673fd09d7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_efb7a2c8-e7fd-4896-9889-ee3018853a1e" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f0e13be-baa9-4a03-bd67-803673fd09d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_8895faae-506c-4339-9117-bec299456b21" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f0e13be-baa9-4a03-bd67-803673fd09d7" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_8895faae-506c-4339-9117-bec299456b21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_bf35ecc7-e0c2-4d0d-be8e-c51edd51549e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f0e13be-baa9-4a03-bd67-803673fd09d7" xlink:to="loc_us-gaap_StockholdersEquity_bf35ecc7-e0c2-4d0d-be8e-c51edd51549e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_c98a58d8-c517-4b1b-9c18-b7c401f3aad7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f0e13be-baa9-4a03-bd67-803673fd09d7" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_c98a58d8-c517-4b1b-9c18-b7c401f3aad7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_0c05b1bf-6a51-4d89-a081-44e57c9652c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f0e13be-baa9-4a03-bd67-803673fd09d7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_0c05b1bf-6a51-4d89-a081-44e57c9652c7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_bbf93ada-7da1-4e46-bae5-166bcc0d0ab5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f0e13be-baa9-4a03-bd67-803673fd09d7" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_bbf93ada-7da1-4e46-bae5-166bcc0d0ab5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_fb8a9892-319c-42ca-9187-3a868d901344" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f0e13be-baa9-4a03-bd67-803673fd09d7" xlink:to="loc_us-gaap_NetIncomeLoss_fb8a9892-319c-42ca-9187-3a868d901344" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_30ccb722-694b-4f28-a14c-b2fdc3a21816" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_8f0e13be-baa9-4a03-bd67-803673fd09d7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_30ccb722-694b-4f28-a14c-b2fdc3a21816" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_63314bee-9dba-4bf7-adee-3bf7e8b544d4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_92be2fc7-f036-40e4-9362-d2c553890669" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/DisaggregatedRevenuesDisaggregationofRevenuesDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#DisaggregatedRevenuesDisaggregationofRevenuesDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/DisaggregatedRevenuesDisaggregationofRevenuesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_2b6930f4-89b9-42bf-9e1a-0e625d424a8a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_d808a906-99fa-48b1-9019-f186a8835f8b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_2b6930f4-89b9-42bf-9e1a-0e625d424a8a" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_d808a906-99fa-48b1-9019-f186a8835f8b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_c7253e4f-230f-4dad-9c7b-98788a119ce9" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_d808a906-99fa-48b1-9019-f186a8835f8b" xlink:to="loc_srt_ProductOrServiceAxis_c7253e4f-230f-4dad-9c7b-98788a119ce9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_c7253e4f-230f-4dad-9c7b-98788a119ce9_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_c7253e4f-230f-4dad-9c7b-98788a119ce9" xlink:to="loc_srt_ProductsAndServicesDomain_c7253e4f-230f-4dad-9c7b-98788a119ce9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_428a2d57-f76a-4173-b7ff-35304e926f10" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_c7253e4f-230f-4dad-9c7b-98788a119ce9" xlink:to="loc_srt_ProductsAndServicesDomain_428a2d57-f76a-4173-b7ff-35304e926f10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_c67164e0-a484-46f5-9d45-1b75bde3b22e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_428a2d57-f76a-4173-b7ff-35304e926f10" xlink:to="loc_us-gaap_ProductMember_c67164e0-a484-46f5-9d45-1b75bde3b22e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_QelbreeMember_9806eb59-f472-4de8-abe5-13cf79da2f72" xlink:href="supn-20240630.xsd#supn_QelbreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c67164e0-a484-46f5-9d45-1b75bde3b22e" xlink:to="loc_supn_QelbreeMember_9806eb59-f472-4de8-abe5-13cf79da2f72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_GOCOVRIMember_5b3b4c7f-40d4-4f37-a50e-318e078511ec" xlink:href="supn-20240630.xsd#supn_GOCOVRIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c67164e0-a484-46f5-9d45-1b75bde3b22e" xlink:to="loc_supn_GOCOVRIMember_5b3b4c7f-40d4-4f37-a50e-318e078511ec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_OxtellarXRMember_834c6859-6f8b-44d9-a10a-2c493a0c2aaa" xlink:href="supn-20240630.xsd#supn_OxtellarXRMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c67164e0-a484-46f5-9d45-1b75bde3b22e" xlink:to="loc_supn_OxtellarXRMember_834c6859-6f8b-44d9-a10a-2c493a0c2aaa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_APOKYNMember_3be70347-1011-4020-bdce-787ce0253bdc" xlink:href="supn-20240630.xsd#supn_APOKYNMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c67164e0-a484-46f5-9d45-1b75bde3b22e" xlink:to="loc_supn_APOKYNMember_3be70347-1011-4020-bdce-787ce0253bdc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_TrokendiXrMember_8d480a8a-4843-462f-ae8f-079ca77a7443" xlink:href="supn-20240630.xsd#supn_TrokendiXrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c67164e0-a484-46f5-9d45-1b75bde3b22e" xlink:to="loc_supn_TrokendiXrMember_8d480a8a-4843-462f-ae8f-079ca77a7443" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManufacturedProductOtherMember_55f680c7-d0bf-4dee-a755-362ada0f8b19" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ManufacturedProductOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductMember_c67164e0-a484-46f5-9d45-1b75bde3b22e" xlink:to="loc_us-gaap_ManufacturedProductOtherMember_55f680c7-d0bf-4dee-a755-362ada0f8b19" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_RoyaltyLicenseAndOtherRevenueMember_0a9fc856-c057-4abc-ab17-9c98b323c0e9" xlink:href="supn-20240630.xsd#supn_RoyaltyLicenseAndOtherRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_428a2d57-f76a-4173-b7ff-35304e926f10" xlink:to="loc_supn_RoyaltyLicenseAndOtherRevenueMember_0a9fc856-c057-4abc-ab17-9c98b323c0e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_0ba3a298-5c20-499c-b0b7-2977196a2201" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_2b6930f4-89b9-42bf-9e1a-0e625d424a8a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_0ba3a298-5c20-499c-b0b7-2977196a2201" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/FairValueofFinancialInstrumentsDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#FairValueofFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/FairValueofFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_d8a4a24f-8a1b-458a-b26f-35403e238658" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7352986c-cd6a-4912-94dc-a5d191418490" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_d8a4a24f-8a1b-458a-b26f-35403e238658" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7352986c-cd6a-4912-94dc-a5d191418490" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4e819480-a3e4-44ff-87e4-4284b6e90d2c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7352986c-cd6a-4912-94dc-a5d191418490" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4e819480-a3e4-44ff-87e4-4284b6e90d2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_4e819480-a3e4-44ff-87e4-4284b6e90d2c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4e819480-a3e4-44ff-87e4-4284b6e90d2c" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_4e819480-a3e4-44ff-87e4-4284b6e90d2c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_b6a145ae-901d-405d-9cbd-aa1f99fdd126" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_4e819480-a3e4-44ff-87e4-4284b6e90d2c" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_b6a145ae-901d-405d-9cbd-aa1f99fdd126" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_b4da8872-f7d0-49e7-a974-3a3b9a631cf5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_b6a145ae-901d-405d-9cbd-aa1f99fdd126" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_b4da8872-f7d0-49e7-a974-3a3b9a631cf5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_eda0db12-1150-48bb-b5ce-d2b49ed80236" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7352986c-cd6a-4912-94dc-a5d191418490" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_eda0db12-1150-48bb-b5ce-d2b49ed80236" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_eda0db12-1150-48bb-b5ce-d2b49ed80236_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_eda0db12-1150-48bb-b5ce-d2b49ed80236" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_eda0db12-1150-48bb-b5ce-d2b49ed80236_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0949cd99-c278-4ca7-86b4-806ed81670a7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_eda0db12-1150-48bb-b5ce-d2b49ed80236" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0949cd99-c278-4ca7-86b4-806ed81670a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_557dbea0-1dce-45d9-80be-2a5d6944037c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0949cd99-c278-4ca7-86b4-806ed81670a7" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_557dbea0-1dce-45d9-80be-2a5d6944037c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_a3de7bfd-2c38-420a-af6e-94655362de89" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0949cd99-c278-4ca7-86b4-806ed81670a7" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_a3de7bfd-2c38-420a-af6e-94655362de89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_86fcc2fc-a11b-4bfa-8844-adf96ce3f4f2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0949cd99-c278-4ca7-86b4-806ed81670a7" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_86fcc2fc-a11b-4bfa-8844-adf96ce3f4f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_1349a86d-779f-4f6c-9bc1-63e74df4abdb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7352986c-cd6a-4912-94dc-a5d191418490" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_1349a86d-779f-4f6c-9bc1-63e74df4abdb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_1349a86d-779f-4f6c-9bc1-63e74df4abdb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_1349a86d-779f-4f6c-9bc1-63e74df4abdb" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_1349a86d-779f-4f6c-9bc1-63e74df4abdb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_46aaac89-2e90-4cbc-bbc3-22f4612e827a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_1349a86d-779f-4f6c-9bc1-63e74df4abdb" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_46aaac89-2e90-4cbc-bbc3-22f4612e827a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashMember_01e8e734-2eee-4d81-bfec-db08b532794b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_46aaac89-2e90-4cbc-bbc3-22f4612e827a" xlink:to="loc_us-gaap_CashMember_01e8e734-2eee-4d81-bfec-db08b532794b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_8a0e9fad-1e1e-4430-a89d-2988c8ceb0aa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_46aaac89-2e90-4cbc-bbc3-22f4612e827a" xlink:to="loc_us-gaap_MoneyMarketFundsMember_8a0e9fad-1e1e-4430-a89d-2988c8ceb0aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_e408d544-1e39-494f-870b-c98085ee4380" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_7352986c-cd6a-4912-94dc-a5d191418490" xlink:to="loc_us-gaap_FinancialInstrumentAxis_e408d544-1e39-494f-870b-c98085ee4380" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e408d544-1e39-494f-870b-c98085ee4380_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e408d544-1e39-494f-870b-c98085ee4380" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e408d544-1e39-494f-870b-c98085ee4380_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c6a70bb9-3286-41f9-8762-1e2a3fafcf22" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e408d544-1e39-494f-870b-c98085ee4380" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c6a70bb9-3286-41f9-8762-1e2a3fafcf22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CorporateAndUSGovernmentAgencyAndMunicipalDebtSecuritiesMember_95a47cd0-7346-48da-9947-3c5c9b730283" xlink:href="supn-20240630.xsd#supn_CorporateAndUSGovernmentAgencyAndMunicipalDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c6a70bb9-3286-41f9-8762-1e2a3fafcf22" xlink:to="loc_supn_CorporateAndUSGovernmentAgencyAndMunicipalDebtSecuritiesMember_95a47cd0-7346-48da-9947-3c5c9b730283" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CorporateAndMunicipalDebtSecuritiesMember_724b2e97-5d9e-4c69-bd3d-d91f88882f5d" xlink:href="supn-20240630.xsd#supn_CorporateAndMunicipalDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_c6a70bb9-3286-41f9-8762-1e2a3fafcf22" xlink:to="loc_supn_CorporateAndMunicipalDebtSecuritiesMember_724b2e97-5d9e-4c69-bd3d-d91f88882f5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_07386133-561b-4271-a42b-13481747d358" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_d8a4a24f-8a1b-458a-b26f-35403e238658" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_07386133-561b-4271-a42b-13481747d358" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAbstract_79cef629-ecd5-4a11-9578-4eb495217370" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_07386133-561b-4271-a42b-13481747d358" xlink:to="loc_us-gaap_CashAndCashEquivalentsAbstract_79cef629-ecd5-4a11-9578-4eb495217370" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_ec35e588-17a5-4f5c-a738-1b97e898617d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsAbstract_79cef629-ecd5-4a11-9578-4eb495217370" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_ec35e588-17a5-4f5c-a738-1b97e898617d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesCurrentAbstract_93890daf-c4c0-4107-8286-7b88ffe0fb14" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_07386133-561b-4271-a42b-13481747d358" xlink:to="loc_us-gaap_DebtSecuritiesCurrentAbstract_93890daf-c4c0-4107-8286-7b88ffe0fb14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestCurrent_4c73b33f-d1b0-4e29-a33e-852d217c8fc9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesCurrentAbstract_93890daf-c4c0-4107-8286-7b88ffe0fb14" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestCurrent_4c73b33f-d1b0-4e29-a33e-852d217c8fc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesNoncurrentAbstract_2e148ed8-ef3c-4e19-937a-781e9f43ae69" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_07386133-561b-4271-a42b-13481747d358" xlink:to="loc_us-gaap_DebtSecuritiesNoncurrentAbstract_2e148ed8-ef3c-4e19-937a-781e9f43ae69" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestNoncurrent_6b7ee39b-a96f-4bd8-b138-5141209be9e1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesNoncurrentAbstract_2e148ed8-ef3c-4e19-937a-781e9f43ae69" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterestNoncurrent_6b7ee39b-a96f-4bd8-b138-5141209be9e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrentAbstract_9fea9b24-f4a2-4f56-8423-855bcf0d69b6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherAssetsNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_07386133-561b-4271-a42b-13481747d358" xlink:to="loc_us-gaap_OtherAssetsNoncurrentAbstract_9fea9b24-f4a2-4f56-8423-855bcf0d69b6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_4fd64c41-81b1-4eff-b650-796a3013a0a6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsNoncurrentAbstract_9fea9b24-f4a2-4f56-8423-855bcf0d69b6" xlink:to="loc_us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_4fd64c41-81b1-4eff-b650-796a3013a0a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_6c74644e-ceeb-4d44-9af7-c6f728e6d451" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_07386133-561b-4271-a42b-13481747d358" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_6c74644e-ceeb-4d44-9af7-c6f728e6d451" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_9c926f7e-2226-41c6-91fc-09dfcc23ccdb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_d8a4a24f-8a1b-458a-b26f-35403e238658" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_9c926f7e-2226-41c6-91fc-09dfcc23ccdb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_083052ab-7afe-47a2-aafd-4ca4ca92ca51" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_9c926f7e-2226-41c6-91fc-09dfcc23ccdb" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_083052ab-7afe-47a2-aafd-4ca4ca92ca51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_5cfbc107-32b9-458e-9e9e-cbbb42112fa5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_9c926f7e-2226-41c6-91fc-09dfcc23ccdb" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_5cfbc107-32b9-458e-9e9e-cbbb42112fa5" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ContingentConsiderationNarrativeDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#ContingentConsiderationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ContingentConsiderationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_9bcb7b22-c3ce-4f7a-b202-ddfd3b7bee65" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_8c56f219-32af-4eeb-b916-5703ce732a19" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9bcb7b22-c3ce-4f7a-b202-ddfd3b7bee65" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_8c56f219-32af-4eeb-b916-5703ce732a19" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_9897bf75-9ea3-4f33-9dbe-06ca28a22e3d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_8c56f219-32af-4eeb-b916-5703ce732a19" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_9897bf75-9ea3-4f33-9dbe-06ca28a22e3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9897bf75-9ea3-4f33-9dbe-06ca28a22e3d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_9897bf75-9ea3-4f33-9dbe-06ca28a22e3d" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9897bf75-9ea3-4f33-9dbe-06ca28a22e3d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_80ce1e7f-2d82-4a92-8afc-5a399f98aec9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_9897bf75-9ea3-4f33-9dbe-06ca28a22e3d" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_80ce1e7f-2d82-4a92-8afc-5a399f98aec9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_9217fabc-15eb-41cc-a40d-39c66f83fb12" xlink:href="supn-20240630.xsd#supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_80ce1e7f-2d82-4a92-8afc-5a399f98aec9" xlink:to="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_9217fabc-15eb-41cc-a40d-39c66f83fb12" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_AdamasMember_f1f257df-14c7-4d19-be4d-156a23f35f87" xlink:href="supn-20240630.xsd#supn_AdamasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_80ce1e7f-2d82-4a92-8afc-5a399f98aec9" xlink:to="loc_supn_AdamasMember_f1f257df-14c7-4d19-be4d-156a23f35f87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_220fd817-5e42-4a01-8597-d2e061d11f34" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_8c56f219-32af-4eeb-b916-5703ce732a19" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_220fd817-5e42-4a01-8597-d2e061d11f34" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_220fd817-5e42-4a01-8597-d2e061d11f34_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_220fd817-5e42-4a01-8597-d2e061d11f34" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_220fd817-5e42-4a01-8597-d2e061d11f34_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_b3845c9a-2c43-4598-b1f8-1ac67d7aae80" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_220fd817-5e42-4a01-8597-d2e061d11f34" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_b3845c9a-2c43-4598-b1f8-1ac67d7aae80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_SPN830NDAApprovalMilestoneMember_d59d06fe-9c69-4309-8a2a-280380acd0f3" xlink:href="supn-20240630.xsd#supn_SPN830NDAApprovalMilestoneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_b3845c9a-2c43-4598-b1f8-1ac67d7aae80" xlink:to="loc_supn_SPN830NDAApprovalMilestoneMember_d59d06fe-9c69-4309-8a2a-280380acd0f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_SubsequentCommercialProductLaunchMember_d1f2438d-64e4-418f-bcb3-7643f9819f17" xlink:href="supn-20240630.xsd#supn_SubsequentCommercialProductLaunchMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_b3845c9a-2c43-4598-b1f8-1ac67d7aae80" xlink:to="loc_supn_SubsequentCommercialProductLaunchMember_d1f2438d-64e4-418f-bcb3-7643f9819f17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_Milestone2024AndMilestone2025Member_1c02d6fb-8e34-45be-afff-050b761f9adc" xlink:href="supn-20240630.xsd#supn_Milestone2024AndMilestone2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_b3845c9a-2c43-4598-b1f8-1ac67d7aae80" xlink:to="loc_supn_Milestone2024AndMilestone2025Member_1c02d6fb-8e34-45be-afff-050b761f9adc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_Milestone2024Member_0881317c-d409-4d81-a231-3a340ccd33cf" xlink:href="supn-20240630.xsd#supn_Milestone2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_supn_Milestone2024AndMilestone2025Member_1c02d6fb-8e34-45be-afff-050b761f9adc" xlink:to="loc_supn_Milestone2024Member_0881317c-d409-4d81-a231-3a340ccd33cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh_d20cf7bb-8dd4-4d34-8ead-6446c0082303" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9bcb7b22-c3ce-4f7a-b202-ddfd3b7bee65" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh_d20cf7bb-8dd4-4d34-8ead-6446c0082303" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_BusinessCombinationContingentConsiderationNumberOfContingentValueRightsPerCommonShare_baccaa94-86f7-4f45-b3d4-510071fd5f71" xlink:href="supn-20240630.xsd#supn_BusinessCombinationContingentConsiderationNumberOfContingentValueRightsPerCommonShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9bcb7b22-c3ce-4f7a-b202-ddfd3b7bee65" xlink:to="loc_supn_BusinessCombinationContingentConsiderationNumberOfContingentValueRightsPerCommonShare_baccaa94-86f7-4f45-b3d4-510071fd5f71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_BusinessCombinationContingentConsiderationArrangementsValuePricePerShare_d2ea7823-2e5c-4a93-a60a-5e1e931ec7a7" xlink:href="supn-20240630.xsd#supn_BusinessCombinationContingentConsiderationArrangementsValuePricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9bcb7b22-c3ce-4f7a-b202-ddfd3b7bee65" xlink:to="loc_supn_BusinessCombinationContingentConsiderationArrangementsValuePricePerShare_d2ea7823-2e5c-4a93-a60a-5e1e931ec7a7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValue_02f92fa9-fc0a-488a-9070-576d6ee76e36" xlink:href="supn-20240630.xsd#supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9bcb7b22-c3ce-4f7a-b202-ddfd3b7bee65" xlink:to="loc_supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValue_02f92fa9-fc0a-488a-9070-576d6ee76e36" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValueTerm_2cff06ab-784d-40d8-bf0c-5c3d79ddb663" xlink:href="supn-20240630.xsd#supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValueTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9bcb7b22-c3ce-4f7a-b202-ddfd3b7bee65" xlink:to="loc_supn_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationExcessAcquisitionDateFairValueTerm_2cff06ab-784d-40d8-bf0c-5c3d79ddb663" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow_8dd165b3-95ec-4588-84b8-95353d31fc99" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9bcb7b22-c3ce-4f7a-b202-ddfd3b7bee65" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueLow_8dd165b3-95ec-4588-84b8-95353d31fc99" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_f980ea6d-fd4f-4408-a851-94b846eb070f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9bcb7b22-c3ce-4f7a-b202-ddfd3b7bee65" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_f980ea6d-fd4f-4408-a851-94b846eb070f" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ContingentConsiderationReconciliationoftheBeginningandEndingBalancesRelatedtotheContingentConsiderationDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#ContingentConsiderationReconciliationoftheBeginningandEndingBalancesRelatedtotheContingentConsiderationDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ContingentConsiderationReconciliationoftheBeginningandEndingBalancesRelatedtotheContingentConsiderationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_e48204d7-acb8-4a69-8ced-86cd5b5219f0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_46c40741-2cff-436f-8237-f06f1bc5bc6d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_e48204d7-acb8-4a69-8ced-86cd5b5219f0" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_46c40741-2cff-436f-8237-f06f1bc5bc6d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_c285a7a7-8c46-436e-b0ec-47e99e8f598e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_46c40741-2cff-436f-8237-f06f1bc5bc6d" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_c285a7a7-8c46-436e-b0ec-47e99e8f598e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c285a7a7-8c46-436e-b0ec-47e99e8f598e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_c285a7a7-8c46-436e-b0ec-47e99e8f598e" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c285a7a7-8c46-436e-b0ec-47e99e8f598e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_45884b5b-f3f7-493a-b18e-dca8a95a49d5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_c285a7a7-8c46-436e-b0ec-47e99e8f598e" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_45884b5b-f3f7-493a-b18e-dca8a95a49d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_6fb20de4-7852-4c3a-959b-cd40d68cc6d4" xlink:href="supn-20240630.xsd#supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_45884b5b-f3f7-493a-b18e-dca8a95a49d5" xlink:to="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_6fb20de4-7852-4c3a-959b-cd40d68cc6d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_AdamasMember_5e64e2c3-9835-42c5-b428-8d11b44d679a" xlink:href="supn-20240630.xsd#supn_AdamasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_45884b5b-f3f7-493a-b18e-dca8a95a49d5" xlink:to="loc_supn_AdamasMember_5e64e2c3-9835-42c5-b428-8d11b44d679a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_b3ef3032-65d7-4216-b2c6-3f4f4e43afe5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_e48204d7-acb8-4a69-8ced-86cd5b5219f0" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_b3ef3032-65d7-4216-b2c6-3f4f4e43afe5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_eccae544-469b-44ed-80a0-02a323d9f5ca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_b3ef3032-65d7-4216-b2c6-3f4f4e43afe5" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_eccae544-469b-44ed-80a0-02a323d9f5ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_85093c53-f4eb-4661-afbe-a8d6fe283a6b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_b3ef3032-65d7-4216-b2c6-3f4f4e43afe5" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_85093c53-f4eb-4661-afbe-a8d6fe283a6b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_c2af5de1-b500-4ade-8456-a200515b837d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/IntangibleAssetsNetIntangibleAssetsGrossCarryingAmountandRelatedAccumulatedAmortizationDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#IntangibleAssetsNetIntangibleAssetsGrossCarryingAmountandRelatedAccumulatedAmortizationDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/IntangibleAssetsNetIntangibleAssetsGrossCarryingAmountandRelatedAccumulatedAmortizationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_d7ddebfd-da74-41ff-82ef-07ade15d6d1d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_f84ffd75-8e71-45d7-9329-67826572cf0d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_d7ddebfd-da74-41ff-82ef-07ade15d6d1d" xlink:to="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_f84ffd75-8e71-45d7-9329-67826572cf0d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_08dba892-ad6e-4b9a-961f-f371575cb0ca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable_f84ffd75-8e71-45d7-9329-67826572cf0d" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_08dba892-ad6e-4b9a-961f-f371575cb0ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_08dba892-ad6e-4b9a-961f-f371575cb0ca_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_08dba892-ad6e-4b9a-961f-f371575cb0ca" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_08dba892-ad6e-4b9a-961f-f371575cb0ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_bfbad937-d252-4b1e-a680-df0a3bae3671" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_08dba892-ad6e-4b9a-961f-f371575cb0ca" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_bfbad937-d252-4b1e-a680-df0a3bae3671" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_ff423d64-ac65-4951-b03b-f5cea1af9e0b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InProcessResearchAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_bfbad937-d252-4b1e-a680-df0a3bae3671" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_ff423d64-ac65-4951-b03b-f5cea1af9e0b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_3d98d8b9-46dc-4346-9438-3e6f69dd3bf1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems_d7ddebfd-da74-41ff-82ef-07ade15d6d1d" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_3d98d8b9-46dc-4346-9438-3e6f69dd3bf1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_97147f4a-e546-4cc9-9943-400828ae5da9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_f73dcee0-a70d-464b-b647-2a1491660df0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_97147f4a-e546-4cc9-9943-400828ae5da9" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_f73dcee0-a70d-464b-b647-2a1491660df0" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0cedae84-a8f1-472d-b969-ecf1b1e75520" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_f73dcee0-a70d-464b-b647-2a1491660df0" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0cedae84-a8f1-472d-b969-ecf1b1e75520" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0cedae84-a8f1-472d-b969-ecf1b1e75520_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0cedae84-a8f1-472d-b969-ecf1b1e75520" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0cedae84-a8f1-472d-b969-ecf1b1e75520_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5c3ad239-d446-46ae-8c44-56a6f89bf8eb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0cedae84-a8f1-472d-b969-ecf1b1e75520" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5c3ad239-d446-46ae-8c44-56a6f89bf8eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_19c40ade-8f76-4271-96aa-b3f384da93d5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5c3ad239-d446-46ae-8c44-56a6f89bf8eb" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_19c40ade-8f76-4271-96aa-b3f384da93d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_PatentDefenseCostsMember_2041e89f-ebce-40c7-a334-a3d7d4025c58" xlink:href="supn-20240630.xsd#supn_PatentDefenseCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_5c3ad239-d446-46ae-8c44-56a6f89bf8eb" xlink:to="loc_supn_PatentDefenseCostsMember_2041e89f-ebce-40c7-a334-a3d7d4025c58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_7ec2c8aa-6b25-4c31-a73c-9c0e75fd45cc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_97147f4a-e546-4cc9-9943-400828ae5da9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsRemainingAmortizationPeriod1_7ec2c8aa-6b25-4c31-a73c-9c0e75fd45cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_43c61fb1-e38d-4ebe-8662-8f698849ac65" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_97147f4a-e546-4cc9-9943-400828ae5da9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_43c61fb1-e38d-4ebe-8662-8f698849ac65" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_ad749026-c3bd-4f33-8374-7778e8928ab4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_97147f4a-e546-4cc9-9943-400828ae5da9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_ad749026-c3bd-4f33-8374-7778e8928ab4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_2905d11d-4ad2-4514-a60e-5782c1ea7294" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_97147f4a-e546-4cc9-9943-400828ae5da9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_2905d11d-4ad2-4514-a60e-5782c1ea7294" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/DebtDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#DebtDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/DebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_46b7c71b-ac04-4b11-bbc1-4b7746e8a7fd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_9fe7bd56-2cf5-4082-99d3-dcae7273270e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_46b7c71b-ac04-4b11-bbc1-4b7746e8a7fd" xlink:to="loc_us-gaap_DebtInstrumentTable_9fe7bd56-2cf5-4082-99d3-dcae7273270e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_ba290690-0f73-4ca5-b829-ec917d95d41f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9fe7bd56-2cf5-4082-99d3-dcae7273270e" xlink:to="loc_us-gaap_CreditFacilityAxis_ba290690-0f73-4ca5-b829-ec917d95d41f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_ba290690-0f73-4ca5-b829-ec917d95d41f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_ba290690-0f73-4ca5-b829-ec917d95d41f" xlink:to="loc_us-gaap_CreditFacilityDomain_ba290690-0f73-4ca5-b829-ec917d95d41f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_e3995948-7a5e-4a4a-b7d0-c0181fa33985" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_ba290690-0f73-4ca5-b829-ec917d95d41f" xlink:to="loc_us-gaap_CreditFacilityDomain_e3995948-7a5e-4a4a-b7d0-c0181fa33985" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_UncommittedSecuredCreditLineMember_1788e0ea-8486-4474-905c-75fb1890b1bd" xlink:href="supn-20240630.xsd#supn_UncommittedSecuredCreditLineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_e3995948-7a5e-4a4a-b7d0-c0181fa33985" xlink:to="loc_supn_UncommittedSecuredCreditLineMember_1788e0ea-8486-4474-905c-75fb1890b1bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_bddd9a86-35eb-4aa5-b7ab-cf414bcddde1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_e3995948-7a5e-4a4a-b7d0-c0181fa33985" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_bddd9a86-35eb-4aa5-b7ab-cf414bcddde1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_705eed7c-ff1b-4f57-bf82-ebc4d3a6dab0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_9fe7bd56-2cf5-4082-99d3-dcae7273270e" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_705eed7c-ff1b-4f57-bf82-ebc4d3a6dab0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_705eed7c-ff1b-4f57-bf82-ebc4d3a6dab0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_705eed7c-ff1b-4f57-bf82-ebc4d3a6dab0" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_705eed7c-ff1b-4f57-bf82-ebc4d3a6dab0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_beb37416-89e2-4ce6-a54b-75bf30012d2f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_705eed7c-ff1b-4f57-bf82-ebc4d3a6dab0" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_beb37416-89e2-4ce6-a54b-75bf30012d2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_f55eb04c-e8a6-4dbf-9219-28e525e1a80e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_beb37416-89e2-4ce6-a54b-75bf30012d2f" xlink:to="loc_us-gaap_LineOfCreditMember_f55eb04c-e8a6-4dbf-9219-28e525e1a80e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_b3677176-eeac-4ec2-9ef0-bbc7a5a9154e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_beb37416-89e2-4ce6-a54b-75bf30012d2f" xlink:to="loc_us-gaap_ConvertibleDebtMember_b3677176-eeac-4ec2-9ef0-bbc7a5a9154e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_751632e3-aea5-4358-952e-2a911c0d95ee" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_46b7c71b-ac04-4b11-bbc1-4b7746e8a7fd" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_751632e3-aea5-4358-952e-2a911c0d95ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_0b923a7c-0302-4c9f-adc0-b6a0a0c4ee82" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_46b7c71b-ac04-4b11-bbc1-4b7746e8a7fd" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_0b923a7c-0302-4c9f-adc0-b6a0a0c4ee82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_316ce325-7c3d-4087-9cc5-3d1a0289f074" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_46b7c71b-ac04-4b11-bbc1-4b7746e8a7fd" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_316ce325-7c3d-4087-9cc5-3d1a0289f074" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_b9d9d5ea-fcf7-432a-b1c0-a4fc0ee77b09" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_46b7c71b-ac04-4b11-bbc1-4b7746e8a7fd" xlink:to="loc_us-gaap_InterestExpenseDebt_b9d9d5ea-fcf7-432a-b1c0-a4fc0ee77b09" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_c756f1d7-5dd1-4811-bfef-277de6dfc188" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_46b7c71b-ac04-4b11-bbc1-4b7746e8a7fd" xlink:to="loc_us-gaap_ShortTermBorrowings_c756f1d7-5dd1-4811-bfef-277de6dfc188" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ShareBasedPaymentsNarrativesDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#ShareBasedPaymentsNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ShareBasedPaymentsNarrativesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_86d336b9-fddc-4ad1-b66d-ca89ada8e2e2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_688365b5-0b1d-4e8f-9bbb-d73331eb8d81" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_86d336b9-fddc-4ad1-b66d-ca89ada8e2e2" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_688365b5-0b1d-4e8f-9bbb-d73331eb8d81" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_453e447e-8711-4c45-ab89-1af3499f3d8e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_688365b5-0b1d-4e8f-9bbb-d73331eb8d81" xlink:to="loc_us-gaap_PlanNameAxis_453e447e-8711-4c45-ab89-1af3499f3d8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_453e447e-8711-4c45-ab89-1af3499f3d8e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_453e447e-8711-4c45-ab89-1af3499f3d8e" xlink:to="loc_us-gaap_PlanNameDomain_453e447e-8711-4c45-ab89-1af3499f3d8e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_0f6a8128-41e7-4f88-a91f-b83568795c53" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_453e447e-8711-4c45-ab89-1af3499f3d8e" xlink:to="loc_us-gaap_PlanNameDomain_0f6a8128-41e7-4f88-a91f-b83568795c53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_A2021EquityIncentivePlanMember_f41c78b0-db9f-4db4-96aa-90e976ad7a0c" xlink:href="supn-20240630.xsd#supn_A2021EquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_0f6a8128-41e7-4f88-a91f-b83568795c53" xlink:to="loc_supn_A2021EquityIncentivePlanMember_f41c78b0-db9f-4db4-96aa-90e976ad7a0c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_98873885-7a44-4024-bafa-8e6207d4a9c3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_86d336b9-fddc-4ad1-b66d-ca89ada8e2e2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_98873885-7a44-4024-bafa-8e6207d4a9c3" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ShareBasedPaymentsSharebasedCompensationExpenseDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#ShareBasedPaymentsSharebasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ShareBasedPaymentsSharebasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_1ffb908d-d156-4bc3-840d-35099c6fdd39" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_31aff612-5cfc-4f5c-826f-08ddabec1141" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_1ffb908d-d156-4bc3-840d-35099c6fdd39" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_31aff612-5cfc-4f5c-826f-08ddabec1141" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_0a2caf66-19d5-45f5-a68a-e2742096f7c3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_31aff612-5cfc-4f5c-826f-08ddabec1141" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_0a2caf66-19d5-45f5-a68a-e2742096f7c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_0a2caf66-19d5-45f5-a68a-e2742096f7c3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_0a2caf66-19d5-45f5-a68a-e2742096f7c3" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_0a2caf66-19d5-45f5-a68a-e2742096f7c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_4c8d2301-e78d-4689-bfcd-f3d8cd4d38d8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_0a2caf66-19d5-45f5-a68a-e2742096f7c3" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_4c8d2301-e78d-4689-bfcd-f3d8cd4d38d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_e7604e60-afa2-421b-8f0b-d59b9480c8f9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4c8d2301-e78d-4689-bfcd-f3d8cd4d38d8" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_e7604e60-afa2-421b-8f0b-d59b9480c8f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_7922d16e-6913-4cfa-b05a-fda45a9c1e1c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4c8d2301-e78d-4689-bfcd-f3d8cd4d38d8" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_7922d16e-6913-4cfa-b05a-fda45a9c1e1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_e75b6550-7ccb-4fa9-a014-02e8462eff1f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_1ffb908d-d156-4bc3-840d-35099c6fdd39" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_e75b6550-7ccb-4fa9-a014-02e8462eff1f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ShareBasedPaymentsSARActivityDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#ShareBasedPaymentsSARActivityDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ShareBasedPaymentsSARActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b443f395-e32e-4c3f-93f5-eb1e78f10f0c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_6d1340d1-32cd-4099-8aef-e559ea51e1f4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b443f395-e32e-4c3f-93f5-eb1e78f10f0c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_6d1340d1-32cd-4099-8aef-e559ea51e1f4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_7b05872e-e1b8-4729-86bf-3d2a87d630ce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_6d1340d1-32cd-4099-8aef-e559ea51e1f4" xlink:to="loc_us-gaap_AwardTypeAxis_7b05872e-e1b8-4729-86bf-3d2a87d630ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7b05872e-e1b8-4729-86bf-3d2a87d630ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_7b05872e-e1b8-4729-86bf-3d2a87d630ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7b05872e-e1b8-4729-86bf-3d2a87d630ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_57739072-2c25-4c4b-96ce-5906972e4318" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_7b05872e-e1b8-4729-86bf-3d2a87d630ce" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_57739072-2c25-4c4b-96ce-5906972e4318" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_StockOptionStockAppreciationRightsMember_8afb6c4c-23a1-4576-8dd2-15610c0daa42" xlink:href="supn-20240630.xsd#supn_StockOptionStockAppreciationRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_57739072-2c25-4c4b-96ce-5906972e4318" xlink:to="loc_supn_StockOptionStockAppreciationRightsMember_8afb6c4c-23a1-4576-8dd2-15610c0daa42" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_86f013c3-3fa3-4f8d-bfa8-ba209974957a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b443f395-e32e-4c3f-93f5-eb1e78f10f0c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_86f013c3-3fa3-4f8d-bfa8-ba209974957a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_27bd820a-4921-4d2c-ae43-6aa7cb8e0953" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_86f013c3-3fa3-4f8d-bfa8-ba209974957a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_27bd820a-4921-4d2c-ae43-6aa7cb8e0953" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_e8135a86-c479-4f45-b674-ed089380dd25" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_86f013c3-3fa3-4f8d-bfa8-ba209974957a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_e8135a86-c479-4f45-b674-ed089380dd25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_a6f2b539-7a22-4c62-95f9-39a11e1e2ee6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_86f013c3-3fa3-4f8d-bfa8-ba209974957a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_a6f2b539-7a22-4c62-95f9-39a11e1e2ee6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_5946e762-6ca3-49e6-9009-9bcb80325679" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_86f013c3-3fa3-4f8d-bfa8-ba209974957a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_5946e762-6ca3-49e6-9009-9bcb80325679" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_741cd7ed-eb24-43fc-9edb-b4bcd165da99" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_72d23dbd-23d9-49c8-a3eb-c7e82d643baa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b443f395-e32e-4c3f-93f5-eb1e78f10f0c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_72d23dbd-23d9-49c8-a3eb-c7e82d643baa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_bfd8d48c-1044-4ef3-9e60-474502654bfb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b443f395-e32e-4c3f-93f5-eb1e78f10f0c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_bfd8d48c-1044-4ef3-9e60-474502654bfb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_599fe35d-81c9-4f9e-b869-07f60222e5ed" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b443f395-e32e-4c3f-93f5-eb1e78f10f0c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_599fe35d-81c9-4f9e-b869-07f60222e5ed" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_fbf680b4-3c15-4801-aaa3-088588824d07" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_599fe35d-81c9-4f9e-b869-07f60222e5ed" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_fbf680b4-3c15-4801-aaa3-088588824d07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_7ecbd63e-dc47-41ab-9bf3-eaf867f6b303" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_599fe35d-81c9-4f9e-b869-07f60222e5ed" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_7ecbd63e-dc47-41ab-9bf3-eaf867f6b303" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_47759ce4-a2cb-4ceb-994f-92370dcf2274" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_599fe35d-81c9-4f9e-b869-07f60222e5ed" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_47759ce4-a2cb-4ceb-994f-92370dcf2274" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_c355b8c9-cc9f-432d-8732-64d8226c453d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_599fe35d-81c9-4f9e-b869-07f60222e5ed" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_c355b8c9-cc9f-432d-8732-64d8226c453d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_897280c3-64db-4ce9-8a80-cd86ed76cd5f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_f7bb0362-cdf2-4ad7-bd16-9571137159a5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b443f395-e32e-4c3f-93f5-eb1e78f10f0c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_f7bb0362-cdf2-4ad7-bd16-9571137159a5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_4890b3fe-6688-4a88-a66e-873dc44f9fa4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b443f395-e32e-4c3f-93f5-eb1e78f10f0c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_4890b3fe-6688-4a88-a66e-873dc44f9fa4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract_7e226340-5c9e-4a52-90d6-3d7d6ec0cafe" xlink:href="supn-20240630.xsd#supn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b443f395-e32e-4c3f-93f5-eb1e78f10f0c" xlink:to="loc_supn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract_7e226340-5c9e-4a52-90d6-3d7d6ec0cafe" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_eeb46097-488d-4cb4-8a3b-00e4a4615f1e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_supn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract_7e226340-5c9e-4a52-90d6-3d7d6ec0cafe" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_eeb46097-488d-4cb4-8a3b-00e4a4615f1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_4f41a329-82c1-47e4-b8d2-c06f0a1fa53f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_supn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract_7e226340-5c9e-4a52-90d6-3d7d6ec0cafe" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_4f41a329-82c1-47e4-b8d2-c06f0a1fa53f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_31d02e64-6294-46c2-afc8-dc69cde211ae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_supn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract_7e226340-5c9e-4a52-90d6-3d7d6ec0cafe" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_31d02e64-6294-46c2-afc8-dc69cde211ae" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ShareBasedPaymentsRestrictedStockUnitsDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#ShareBasedPaymentsRestrictedStockUnitsDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ShareBasedPaymentsRestrictedStockUnitsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_13e7752a-c22f-4352-8df7-36f308bc3439" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dd09c9f6-1be9-43ec-877f-43ae8b68efb2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_13e7752a-c22f-4352-8df7-36f308bc3439" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dd09c9f6-1be9-43ec-877f-43ae8b68efb2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_fd0802c1-0564-4635-8db2-5e3b88230ee9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dd09c9f6-1be9-43ec-877f-43ae8b68efb2" xlink:to="loc_us-gaap_AwardTypeAxis_fd0802c1-0564-4635-8db2-5e3b88230ee9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_fd0802c1-0564-4635-8db2-5e3b88230ee9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_fd0802c1-0564-4635-8db2-5e3b88230ee9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_fd0802c1-0564-4635-8db2-5e3b88230ee9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1237ea78-c198-41c8-ae50-3c08b5867dd7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_fd0802c1-0564-4635-8db2-5e3b88230ee9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1237ea78-c198-41c8-ae50-3c08b5867dd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_0dd2554b-646c-47f4-9a46-a0a1c50028e1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1237ea78-c198-41c8-ae50-3c08b5867dd7" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_0dd2554b-646c-47f4-9a46-a0a1c50028e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1b5b5c75-7814-42d1-9fe8-a6bf7479e5f2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_13e7752a-c22f-4352-8df7-36f308bc3439" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1b5b5c75-7814-42d1-9fe8-a6bf7479e5f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_5c331cf7-a07e-4235-90d2-8060f381809c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1b5b5c75-7814-42d1-9fe8-a6bf7479e5f2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_5c331cf7-a07e-4235-90d2-8060f381809c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_9388c52f-71f3-423f-8ffe-f871b471768a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1b5b5c75-7814-42d1-9fe8-a6bf7479e5f2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_9388c52f-71f3-423f-8ffe-f871b471768a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_d9f6738d-44b9-42e1-830b-450a8e0d1521" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1b5b5c75-7814-42d1-9fe8-a6bf7479e5f2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_d9f6738d-44b9-42e1-830b-450a8e0d1521" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_4db1fabf-7e95-4eaa-b008-b73ff656326e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_1b5b5c75-7814-42d1-9fe8-a6bf7479e5f2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_4db1fabf-7e95-4eaa-b008-b73ff656326e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_cf0efbc4-3cdd-4f7a-a288-f3c5cf49632f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_dff8d9ba-ae8a-4dae-8466-b3339b25d9e9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_13e7752a-c22f-4352-8df7-36f308bc3439" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_dff8d9ba-ae8a-4dae-8466-b3339b25d9e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_6a49f6da-61eb-4ce0-b287-215256d2e727" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_dff8d9ba-ae8a-4dae-8466-b3339b25d9e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_6a49f6da-61eb-4ce0-b287-215256d2e727" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_0274b3cb-d95f-45f9-8de8-f01934be29aa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_dff8d9ba-ae8a-4dae-8466-b3339b25d9e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_0274b3cb-d95f-45f9-8de8-f01934be29aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_322a3146-d7ea-4d92-ab7b-4fa854210adf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_dff8d9ba-ae8a-4dae-8466-b3339b25d9e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_322a3146-d7ea-4d92-ab7b-4fa854210adf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_3c2c6dd6-9f38-4857-80bb-b401f3096097" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_dff8d9ba-ae8a-4dae-8466-b3339b25d9e9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_3c2c6dd6-9f38-4857-80bb-b401f3096097" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_364e2035-8511-4219-9cff-0182fad8f685" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/ShareBasedPaymentsPerformanceStockUnitsDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#ShareBasedPaymentsPerformanceStockUnitsDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/ShareBasedPaymentsPerformanceStockUnitsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24b948a5-0274-4930-a1bf-e5b3058a519a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_85909e31-668d-4a51-9fbf-f890192be469" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24b948a5-0274-4930-a1bf-e5b3058a519a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_85909e31-668d-4a51-9fbf-f890192be469" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_e450172e-8a58-424e-b1b1-d53c29a04bf5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_85909e31-668d-4a51-9fbf-f890192be469" xlink:to="loc_us-gaap_AwardTypeAxis_e450172e-8a58-424e-b1b1-d53c29a04bf5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e450172e-8a58-424e-b1b1-d53c29a04bf5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_e450172e-8a58-424e-b1b1-d53c29a04bf5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e450172e-8a58-424e-b1b1-d53c29a04bf5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ce03caf6-02a8-4fae-9daa-f2fa4daa75f6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_e450172e-8a58-424e-b1b1-d53c29a04bf5" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ce03caf6-02a8-4fae-9daa-f2fa4daa75f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_054f88e0-22e6-4483-b5ef-f34708c9f661" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ce03caf6-02a8-4fae-9daa-f2fa4daa75f6" xlink:to="loc_us-gaap_PerformanceSharesMember_054f88e0-22e6-4483-b5ef-f34708c9f661" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_PerformanceBasedUnitsMember_34af46d8-3852-4eeb-87ee-2af9ca34c073" xlink:href="supn-20240630.xsd#supn_PerformanceBasedUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PerformanceSharesMember_054f88e0-22e6-4483-b5ef-f34708c9f661" xlink:to="loc_supn_PerformanceBasedUnitsMember_34af46d8-3852-4eeb-87ee-2af9ca34c073" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_MarketBasedUnitsMember_de0d23e1-411c-4182-a914-98bd8463664b" xlink:href="supn-20240630.xsd#supn_MarketBasedUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PerformanceSharesMember_054f88e0-22e6-4483-b5ef-f34708c9f661" xlink:to="loc_supn_MarketBasedUnitsMember_de0d23e1-411c-4182-a914-98bd8463664b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_cffbd18d-c150-4061-83a1-72f77d5b9985" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24b948a5-0274-4930-a1bf-e5b3058a519a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_cffbd18d-c150-4061-83a1-72f77d5b9985" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_10064c05-c9f0-4695-b5a4-0bdfcfbc4d92" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_cffbd18d-c150-4061-83a1-72f77d5b9985" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_10064c05-c9f0-4695-b5a4-0bdfcfbc4d92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_a0bdc48b-144f-405f-b65e-f99ab7d0d805" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_cffbd18d-c150-4061-83a1-72f77d5b9985" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_a0bdc48b-144f-405f-b65e-f99ab7d0d805" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_e92e50ac-49ff-401e-8685-940eb5ec0edc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_cffbd18d-c150-4061-83a1-72f77d5b9985" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_e92e50ac-49ff-401e-8685-940eb5ec0edc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_930f3648-0431-4ce7-b47c-9c3886409314" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_cffbd18d-c150-4061-83a1-72f77d5b9985" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_930f3648-0431-4ce7-b47c-9c3886409314" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_4a2de444-85af-4dff-806d-2685c5f1adad" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_22220ec8-0064-4450-98f3-2847d267590f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24b948a5-0274-4930-a1bf-e5b3058a519a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_22220ec8-0064-4450-98f3-2847d267590f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_66df8234-2030-4a23-9cbb-3822c41dca28" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_22220ec8-0064-4450-98f3-2847d267590f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_66df8234-2030-4a23-9cbb-3822c41dca28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_32eb60b6-1a27-4ddc-a93f-b5ae07a0d7f1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_22220ec8-0064-4450-98f3-2847d267590f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_32eb60b6-1a27-4ddc-a93f-b5ae07a0d7f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_92b1c353-7618-498b-99e4-285c43eac981" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_22220ec8-0064-4450-98f3-2847d267590f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_92b1c353-7618-498b-99e4-285c43eac981" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_e4276d1d-e2cb-4220-bd96-f7162d2b7c65" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_22220ec8-0064-4450-98f3-2847d267590f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_e4276d1d-e2cb-4220-bd96-f7162d2b7c65" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_0e773623-4b72-4098-80de-3f7661471f12" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/EarningsLossperShareScheduleofCommonStockEquivalentsExcludedintheCalculationofDilutedEarningsperShareDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#EarningsLossperShareScheduleofCommonStockEquivalentsExcludedintheCalculationofDilutedEarningsperShareDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/EarningsLossperShareScheduleofCommonStockEquivalentsExcludedintheCalculationofDilutedEarningsperShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_875b0c4c-1ae4-4a25-bc80-3d2c8f4ff7a6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_44bee13a-acfc-48a8-8683-a20eb4f85cd5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_875b0c4c-1ae4-4a25-bc80-3d2c8f4ff7a6" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_44bee13a-acfc-48a8-8683-a20eb4f85cd5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_aff9f705-c1bd-4edf-b4c0-bfdba46662ce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_44bee13a-acfc-48a8-8683-a20eb4f85cd5" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_aff9f705-c1bd-4edf-b4c0-bfdba46662ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_aff9f705-c1bd-4edf-b4c0-bfdba46662ce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_aff9f705-c1bd-4edf-b4c0-bfdba46662ce" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_aff9f705-c1bd-4edf-b4c0-bfdba46662ce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_d9a3cc60-5cf9-4695-a092-eb2e06d25f6a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_aff9f705-c1bd-4edf-b4c0-bfdba46662ce" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_d9a3cc60-5cf9-4695-a092-eb2e06d25f6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_289856b8-7611-4cae-bcb8-b14e9b2ad764" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_d9a3cc60-5cf9-4695-a092-eb2e06d25f6a" xlink:to="loc_us-gaap_ConvertibleDebtMember_289856b8-7611-4cae-bcb8-b14e9b2ad764" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_1e6a3919-1fd4-47b3-a1eb-a6951645e57d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_d9a3cc60-5cf9-4695-a092-eb2e06d25f6a" xlink:to="loc_us-gaap_StockCompensationPlanMember_1e6a3919-1fd4-47b3-a1eb-a6951645e57d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_cf2c726e-248d-4d60-8e5b-71a769b9a184" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_875b0c4c-1ae4-4a25-bc80-3d2c8f4ff7a6" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_cf2c726e-248d-4d60-8e5b-71a769b9a184" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/CompositionofOtherBalanceSheetItemsPropertyandEquipmentDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#CompositionofOtherBalanceSheetItemsPropertyandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/CompositionofOtherBalanceSheetItemsPropertyandEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_fb5691de-b580-4655-a810-e8c577b38850" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_ab4e7f89-34cd-4b8d-9644-46e52de70083" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_fb5691de-b580-4655-a810-e8c577b38850" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_ab4e7f89-34cd-4b8d-9644-46e52de70083" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_55709a30-2069-4ea3-bd4e-ac2951594edd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_ab4e7f89-34cd-4b8d-9644-46e52de70083" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_55709a30-2069-4ea3-bd4e-ac2951594edd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_55709a30-2069-4ea3-bd4e-ac2951594edd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_55709a30-2069-4ea3-bd4e-ac2951594edd" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_55709a30-2069-4ea3-bd4e-ac2951594edd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_808b7a4f-bf78-4456-9cc3-6ddcd4b1e60e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_55709a30-2069-4ea3-bd4e-ac2951594edd" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_808b7a4f-bf78-4456-9cc3-6ddcd4b1e60e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_LabEquipmentAndFurnitureMember_434a52a4-cfbf-408e-ba16-b5f40c435706" xlink:href="supn-20240630.xsd#supn_LabEquipmentAndFurnitureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_808b7a4f-bf78-4456-9cc3-6ddcd4b1e60e" xlink:to="loc_supn_LabEquipmentAndFurnitureMember_434a52a4-cfbf-408e-ba16-b5f40c435706" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_da9aa0e6-0467-486e-af8b-df013a1ce2c5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_808b7a4f-bf78-4456-9cc3-6ddcd4b1e60e" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_da9aa0e6-0467-486e-af8b-df013a1ce2c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_a413ca4a-4b71-43cd-a706-8fc8e901584e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_808b7a4f-bf78-4456-9cc3-6ddcd4b1e60e" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_a413ca4a-4b71-43cd-a706-8fc8e901584e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_da899e83-5fbc-482a-b234-35bd065803f0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ComputerEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_808b7a4f-bf78-4456-9cc3-6ddcd4b1e60e" xlink:to="loc_us-gaap_ComputerEquipmentMember_da899e83-5fbc-482a-b234-35bd065803f0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_531f3adf-e98c-4c11-8e76-f365286fd9bb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_fb5691de-b580-4655-a810-e8c577b38850" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_531f3adf-e98c-4c11-8e76-f365286fd9bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_0f8eeb2d-40ac-46fd-aa64-20f8fc58bc45" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_fb5691de-b580-4655-a810-e8c577b38850" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_0f8eeb2d-40ac-46fd-aa64-20f8fc58bc45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_9d992841-5908-478f-9bf8-5453befcf892" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_fb5691de-b580-4655-a810-e8c577b38850" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_9d992841-5908-478f-9bf8-5453befcf892" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_3a0629d4-ca7d-44b9-9fc6-c528cfef1273" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_fb5691de-b580-4655-a810-e8c577b38850" xlink:to="loc_us-gaap_DepreciationAndAmortization_3a0629d4-ca7d-44b9-9fc6-c528cfef1273" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.supernus.com/role/CommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="supn-20240630.xsd#CommitmentsandContingenciesDetails"/>
  <link:definitionLink xlink:role="http://www.supernus.com/role/CommitmentsandContingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermPurchaseCommitmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentTable_47366336-778c-40fd-aa0d-59ff9df6e630" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermPurchaseCommitmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentTable_47366336-778c-40fd-aa0d-59ff9df6e630" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_cf75bc43-629a-4d85-9913-13d844e35964" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_47366336-778c-40fd-aa0d-59ff9df6e630" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_cf75bc43-629a-4d85-9913-13d844e35964" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cf75bc43-629a-4d85-9913-13d844e35964_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_cf75bc43-629a-4d85-9913-13d844e35964" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cf75bc43-629a-4d85-9913-13d844e35964_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bbc12135-5695-42a0-9b8b-9b137c16363d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_cf75bc43-629a-4d85-9913-13d844e35964" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bbc12135-5695-42a0-9b8b-9b137c16363d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_ca0cd59d-ecec-46ef-aeaa-8756e8f7b267" xlink:href="supn-20240630.xsd#supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bbc12135-5695-42a0-9b8b-9b137c16363d" xlink:to="loc_supn_MDDUSEnterprisesLLCFormerlyUSWMEnterprisesMember_ca0cd59d-ecec-46ef-aeaa-8756e8f7b267" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_a9bd9e25-965e-4051-842a-019f80b8354c" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_47366336-778c-40fd-aa0d-59ff9df6e630" xlink:to="loc_srt_LitigationCaseAxis_a9bd9e25-965e-4051-842a-019f80b8354c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_a9bd9e25-965e-4051-842a-019f80b8354c_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_a9bd9e25-965e-4051-842a-019f80b8354c" xlink:to="loc_srt_LitigationCaseTypeDomain_a9bd9e25-965e-4051-842a-019f80b8354c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_d20d8eff-8e2c-40f9-8253-c18e7fb46661" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_a9bd9e25-965e-4051-842a-019f80b8354c" xlink:to="loc_srt_LitigationCaseTypeDomain_d20d8eff-8e2c-40f9-8253-c18e7fb46661" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_NAMENDAXRNamzaricQuiTamLitigationMember_903cf39c-2474-426f-af83-04a6a1627b5c" xlink:href="supn-20240630.xsd#supn_NAMENDAXRNamzaricQuiTamLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_d20d8eff-8e2c-40f9-8253-c18e7fb46661" xlink:to="loc_supn_NAMENDAXRNamzaricQuiTamLitigationMember_903cf39c-2474-426f-af83-04a6a1627b5c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_cd1083ff-2d09-452a-8dff-f2dae1d70edd" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_47366336-778c-40fd-aa0d-59ff9df6e630" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_cd1083ff-2d09-452a-8dff-f2dae1d70edd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_cd1083ff-2d09-452a-8dff-f2dae1d70edd_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_cd1083ff-2d09-452a-8dff-f2dae1d70edd" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_cd1083ff-2d09-452a-8dff-f2dae1d70edd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_a555077b-d2f3-41a7-917a-83bdc92c0c14" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_cd1083ff-2d09-452a-8dff-f2dae1d70edd" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_a555077b-d2f3-41a7-917a-83bdc92c0c14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_NavitorPharmaceuticalsIncMember_6ea0313a-34d7-403f-99af-502df59b2aa2" xlink:href="supn-20240630.xsd#supn_NavitorPharmaceuticalsIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_a555077b-d2f3-41a7-917a-83bdc92c0c14" xlink:to="loc_supn_NavitorPharmaceuticalsIncMember_6ea0313a-34d7-403f-99af-502df59b2aa2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_0f3c3db9-d546-4b00-9835-5f2b2e37a375" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_47366336-778c-40fd-aa0d-59ff9df6e630" xlink:to="loc_srt_ConsolidatedEntitiesAxis_0f3c3db9-d546-4b00-9835-5f2b2e37a375" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_0f3c3db9-d546-4b00-9835-5f2b2e37a375_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_0f3c3db9-d546-4b00-9835-5f2b2e37a375" xlink:to="loc_srt_ConsolidatedEntitiesDomain_0f3c3db9-d546-4b00-9835-5f2b2e37a375_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_dec1cf28-b701-4345-a0b8-a41813673540" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_0f3c3db9-d546-4b00-9835-5f2b2e37a375" xlink:to="loc_srt_ConsolidatedEntitiesDomain_dec1cf28-b701-4345-a0b8-a41813673540" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_dcf30377-1469-4626-bb43-ecdf1be83f34" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_dec1cf28-b701-4345-a0b8-a41813673540" xlink:to="loc_us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember_dcf30377-1469-4626-bb43-ecdf1be83f34" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_bb9018ac-7f94-483e-a956-2d448580fd4b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_47366336-778c-40fd-aa0d-59ff9df6e630" xlink:to="loc_srt_RangeAxis_bb9018ac-7f94-483e-a956-2d448580fd4b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_bb9018ac-7f94-483e-a956-2d448580fd4b_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_bb9018ac-7f94-483e-a956-2d448580fd4b" xlink:to="loc_srt_RangeMember_bb9018ac-7f94-483e-a956-2d448580fd4b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_17d437cd-cdc8-47fd-b840-b613125b7db7" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_bb9018ac-7f94-483e-a956-2d448580fd4b" xlink:to="loc_srt_RangeMember_17d437cd-cdc8-47fd-b840-b613125b7db7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_07de8e97-1491-43c9-8cbe-d9804e650e4f" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_17d437cd-cdc8-47fd-b840-b613125b7db7" xlink:to="loc_srt_MinimumMember_07de8e97-1491-43c9-8cbe-d9804e650e4f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_0e28e352-06bb-4269-86ce-06481fade4e8" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_17d437cd-cdc8-47fd-b840-b613125b7db7" xlink:to="loc_srt_MaximumMember_0e28e352-06bb-4269-86ce-06481fade4e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CollaborativeArrangementAgreementTerminationNoticePeriod_ceace0d4-82e3-4026-94e5-2c67d9997177" xlink:href="supn-20240630.xsd#supn_CollaborativeArrangementAgreementTerminationNoticePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_supn_CollaborativeArrangementAgreementTerminationNoticePeriod_ceace0d4-82e3-4026-94e5-2c67d9997177" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CollaborativeArrangementThresholdForDevelopmentCostsPayments_d785afb3-f0ae-4f4a-8684-11f027f70f91" xlink:href="supn-20240630.xsd#supn_CollaborativeArrangementThresholdForDevelopmentCostsPayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_supn_CollaborativeArrangementThresholdForDevelopmentCostsPayments_d785afb3-f0ae-4f4a-8684-11f027f70f91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCost_4b52cacf-ea71-44bb-8a2b-b696f2313e7f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquitySecuritiesFvNiCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCost_4b52cacf-ea71-44bb-8a2b-b696f2313e7f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityOwnershipPercentage_be32a30b-6925-46a4-9033-48bb5b42fa9e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableInterestEntityOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_us-gaap_VariableInterestEntityOwnershipPercentage_be32a30b-6925-46a4-9033-48bb5b42fa9e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CollaborativeArrangementPaymentForOneTimeFee_3c0f50f3-d228-433c-b772-7dbc02b9ba97" xlink:href="supn-20240630.xsd#supn_CollaborativeArrangementPaymentForOneTimeFee"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_supn_CollaborativeArrangementPaymentForOneTimeFee_3c0f50f3-d228-433c-b772-7dbc02b9ba97" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CollaborativeArrangementExpectedDevelopmentCosts_4a55db2b-5165-436e-a6fd-d93ec6cb6d06" xlink:href="supn-20240630.xsd#supn_CollaborativeArrangementExpectedDevelopmentCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_supn_CollaborativeArrangementExpectedDevelopmentCosts_4a55db2b-5165-436e-a6fd-d93ec6cb6d06" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_CollaborativeArrangementUpfrontDevelopmentCosts_2e7cf7b8-d0e2-4f8a-b6fd-7612d8fe09eb" xlink:href="supn-20240630.xsd#supn_CollaborativeArrangementUpfrontDevelopmentCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_supn_CollaborativeArrangementUpfrontDevelopmentCosts_2e7cf7b8-d0e2-4f8a-b6fd-7612d8fe09eb" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_PurchaseCommitmentAnnualMinimumAmountCommitted_ad211169-9b8a-4c8d-9f18-82deb75c760b" xlink:href="supn-20240630.xsd#supn_PurchaseCommitmentAnnualMinimumAmountCommitted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_supn_PurchaseCommitmentAnnualMinimumAmountCommitted_ad211169-9b8a-4c8d-9f18-82deb75c760b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_59b66a7c-ca50-4604-8094-15974de00870" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_59b66a7c-ca50-4604-8094-15974de00870" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyDamagesSoughtValue_bc501883-7d62-4e5d-b043-fa5177998e36" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingencyDamagesSoughtValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_6001635c-bd81-4a9e-bf22-b0eecd750460" xlink:to="loc_us-gaap_LossContingencyDamagesSoughtValue_bc501883-7d62-4e5d-b043-fa5177998e36" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#AwardTypeOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_StockOptionStockAppreciationRightsMember_7779016e-5290-431f-82af-6a96540208b3" xlink:href="supn-20240630.xsd#supn_StockOptionStockAppreciationRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_supn_StockOptionStockAppreciationRightsMember_7779016e-5290-431f-82af-6a96540208b3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_PerformanceBasedUnitsMember_4808e4c7-1b2c-438d-9ea4-564e624024d2" xlink:href="supn-20240630.xsd#supn_PerformanceBasedUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_supn_PerformanceBasedUnitsMember_4808e4c7-1b2c-438d-9ea4-564e624024d2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_supn_MarketBasedUnitsMember_114d8a16-0f62-41c0-aaf5-d7c1a1dcfc4e" xlink:href="supn-20240630.xsd#supn_MarketBasedUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_supn_MarketBasedUnitsMember_114d8a16-0f62-41c0-aaf5-d7c1a1dcfc4e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_PerformanceSharesMember" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-roles-2024.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_OtherAssetsNoncurrent" xlink:type="arc" order="1"/>
  </link:definitionLink>
</link:linkbase>
