September 21, 2018

Jack A. Khattar
President and Chief Executive Officer
Supernus Pharmaceuticals, Inc.
1550 East Gude Drive
Rockville, MD 20850

       Re: Supernus Pharmaceuticals, Inc.
           Form 10-K for the Fiscal Year Ended December 31, 2017
           Filed March 1, 2018
           File No. 001-35518

Dear Mr. Khattar:

       We have limited our review of your filing to the financial statements
and related
disclosures and have the following comments. In our comments, we ask you to
provide us with
information so we may better understand your disclosure.

       Please respond to these comments within 10 business days by providing
the requested
information or advise us as soon as possible when you will respond. If you do
not believe our
comments apply to your facts and circumstances, please tell us why in your
response.

       After reviewing your response to these comments, we may have additional
comments.

Form 10-K for the Fiscal Year Ended December 31, 2017

Management's Discussion and Analysis of Financial Condition and Results of
Operations
Critical Account Policies and Use of Estimates
Revenue Recognition, page 64

1.    You identify product revenue recognition as a critical accounting
estimate. Given the
      magnitude of your net product sales and your gross-to-net adjustments as
previously
      conveyed in your quarterly earnings conference calls, please address the
following:
        Provide us a roll forward of the accrual of each gross-to-net
adjustment type (whether
         reflected as an allowance against accounts receivable or a liability)
that depicts
         the following for each annual period from January 1, 2016 to December
31, 2017 and
         for the six-month period from January 1, 2018 to June 30, 3018:
         o   Beginning balance;
 Jack A. Khattar
Supernus Pharmaceuticals, Inc.
September 21, 2018
Page 2

             o   Current provision related to sales made in current period;
             o   Current provision related to sales made in prior periods;
             o   Actual returns or credits in current period related to sales
made in current period;
             o   Actual returns or credits in current period related to sales
made in prior
                 periods; and
             o   Ending balance.
             Tell us the amount of and reason for significant fluctuations in
the provision from
             period to period for each type of gross-to-net adjustment, and the
amount and reason
             that changes in your estimates of these items had on your revenues
and operations.
             Tell us why the balance of your accrued sales deductions is
greater than your net
             accounts receivable at December 31, 2016 and 2017.

Notes to Consolidated Financial Statements
Summary of Significant Accounting Policies
Inventories, page 86

2.       Please confirm for us whether you reflect your inventories at the
lower of cost or net
         realizable value under ASC 330-10-35-1B as added by ASU 2015-11
instead of the
         disclosed lower of cost or market. If so, represent to us that you
will modify your policy
         disclosures in future periodic reports accordingly. Otherwise, please
advise.
       In closing, we remind you that the company and its management are
responsible for the
accuracy and adequacy of their disclosures, notwithstanding any review,
comments, action or
absence of action by the staff.

      You may contact Bonnie Baynes at (202) 551-4924 or Mark Brunhofer at
(202) 551-
3638 with any questions.



FirstName LastNameJack A. Khattar                               Sincerely,
Comapany NameSupernus Pharmaceuticals, Inc.
                                                                Division of
Corporation Finance
September 21, 2018 Page 2                                       Office of
Healthcare & Insurance
FirstName LastName