<PAGE>




                                                                   EXHIBIT 10.48


                           CRITICAL THERAPEUTICS, INC.
           AMENDMENT NO. 2 TO CONSULTING AGREEMENT, AMENDMENT NO. 1 TO
                     APPROVAL AGREEMENT AND MUTUAL RELEASE

         This Amendment No. 2 to Consulting Agreement, Amendment No. 1 to
Approval Agreement, and Mutual Release dated January 29, 2007 (this "Amendment")
to the Consulting Agreement dated January 31, 2001 between Critical
Therapeutics, Inc., a Delaware corporation (the "Company"), and Kevin J. Tracey,
M.D. (the "Consultant"), as amended on January 16, 2003 (the "Consulting
Agreement") and to that certain Approval Agreement dated March 7, 2006 by and
between the Company and the Consultant (the "Approval Agreement") is hereby
entered into by the Company and the Consultant. Each of the Company and the
Consultant are sometimes hereinafter referred to as a "Party" and collectively
as the "Parties".

                                    RECITALS:

         A. The Company and the Consultant are parties to (i) the Consulting
Agreement, (ii) the Approval Agreement, and (iii) that certain Confidentiality
Agreement dated as of March 7, 2006 by and between the Company and the
Consultant (the "Founder Confidentiality Agreement").

         B. The Consultant is a stockholder of Innovative Metabolics, Inc., a
Delaware corporation ("IMI").

         C. The Company and IMI are parties to (i) that certain Confidentiality
Agreement dated as of March 7, 2006 (the "Original Confidentiality Agreement"),
(ii) that certain Confidential Disclosure Agreement dated as of the date hereof
(the "Final CDA") and (iii) that certain Exclusive License Agreement dated as of
the date hereof (the "License Agreement").

         D. The Company and the Consultant desire to make certain amendments to
the Consulting Agreement and the Approval Agreement, to grant certain releases
and to coordinate certain matters relating to the Founder Confidentiality
Agreement, the Original Confidentiality Agreement, the Final CDA and the License
Agreement.

         E. Capitalized terms used herein and not otherwise defined shall have
the meanings assigned to them in the Consulting Agreement.

         NOW, THEREFORE, for valuable consideration, receipt of which is
acknowledged, the Parties hereto agree as follows:

         1. Amendments to the Consulting Agreement.  Acting in accordance with
Section 8.5 of the Consulting Agreement, the Consulting Agreement is hereby
amended as follows:


            a.   Section 1.3 shall be deleted in its entirety and a new Section
                 1.3 shall be inserted in lieu thereof, which shall read as
                 follows:

<PAGE>

                  "1.3 Commitment. The Consultant agrees to make himself
                  available to render the Services from time to time as
                  requested by the Company at such times and locations as may be
                  mutually agreed, provided that the Consultant shall not be
                  required to devote time equivalent to more than 48 hours per
                  year to the performance of the Services."

            b.   Section 2 shall be deleted in its entirety and a new Section 2
                 shall be inserted in lieu thereof, which shall read as follows:

                  "2. Term. Subject to Section 7, this Agreement will be for a
                  term beginning as of January 31, 2001 and ending on January 1,
                  2008."

            c.   Subsection 3.1 shall be deleted in its entirety and a new
                 Subsection 3.1 shall be inserted in lieu thereof, which shall
                 read as follows:

                  "3.1 Compensation. As full compensation for the Services, the
                  Company shall pay the Consultant the following:

                  (a) for the first six years of the term of this Agreement (i)
                  $75,000 during the first year of this Agreement, (ii) $137,250
                  during the second year of this Agreement, (iii) $139,567.50
                  during the third year of this Agreement, (iv) $141,954.53
                  during the fourth year of this Agreement, (v) $144,413.17
                  during the fifth year of this Agreement, and (vi) $146,945.57
                  during the sixth year of this Agreement, in each case payable
                  bi-weekly in arrears.

                  (b) for the period February 1, 2007 through January 1, 2008 of
                  the term of this Agreement, the sum of $500 per month, payable
                  quarterly on the 15th calendar day after the end of such
                  quarter."

For the purposes of the Consulting Agreement, notwithstanding any other
provision or agreement, the Consultant and the Company hereby expressly agree
that

     (i)    the term "Field" as used in the Consulting Agreement shall not
            include the "Field" as defined in the License Agreement, as amended
            and restated at any time hereafter; provided, however, if the
            License Agreement is terminated by either party for any reason, then
            as of the effective date of such termination the term "Field" as
            used in the Consulting Agreement shall thereafter include "Field" as
            defined in the License Agreement, as amended and restated at any
            time hereafter;

     (ii)   payments due to the Consultant pursuant to Section 3.3 of the
            Consulting Agreement shall neither include nor reflect any payments
            of any nature received by the Company from IMI, IMI's Sublicensed
            Affiliates or Sublicensed Third Parties (each as defined in the
            License Agreement) under the terms of the License Agreement,
            including, without limitation, any royalties, upfront payments,
            license fees, or milestone payments in connection with any sales or
            licensing of Products by the Company to IMI, IMI's



                                       2
<PAGE>

            Sublicensed Affiliates or Sublicensed Third Parties or any royalties
            paid by IMI, IMI's Sublicensed Affiliates or Sublicensed Third
            Parties to the Company in respect of Products (collectively, the
            "Excluded Royalties");

     (iii)  the term "royalty payments" as used in Sections 3.3(a)(ii) and
            3.3(b)(ii) of the Consulting Agreement shall include only royalties
            and sublicensing royalties based upon sales of Products received by
            the Company or its Affiliates from a party other than IMI, IMI's
            Sublicensed Affiliates or Sublicensed Third Parties;

     (iv)   the term "royalty payments" as used in Sections 3.3(a)(ii) and
            3.3(b)(ii) of the Consulting Agreement specifically shall not
            include (1) any milestone payments, (2) any upfront fees, (3) any
            license or sublicense fees, or (4) other payments that are not
            related to royalties on sales that are received by the Company and
            the Company's Affiliates in connection with the Products; and

     (v)    the Company's obligations to pay the Consultant royalties pursuant
            to Section 3.3 of the Consulting Agreement shall survive termination
            of the Consulting Agreement for so long as the Company is obligated
            to make payments to the Institution related to the development
            and/or commercialization of Products.

In all other respects, the Consulting Agreement is hereby ratified and confirmed
and remains in full force and effect.

     2.   Release by Consultant. Subject to Section 5, in consideration of
mutual promises contained in this Amendment, the Consultant voluntarily and of
his own free will:


            a.   acknowledges and agrees that (i) the Company has paid all
                 amounts owed to the Consultant under the Consulting Agreement
                 as of the date hereof and (ii) the Company is not and will not
                 be obligated to make any further payments to the Consultant
                 under the Consulting Agreement, except as specifically set
                 forth in new Subsection 3.1(b) of the Consulting Agreement as
                 set forth in Section 1.c of this Amendment and in Section 3.3
                 of the Consulting Agreement, as clarified by this Amendment;
                 provided, however, that the Consultant acknowledges and agrees
                 that Section 3.3 of the Consulting Agreement shall not apply
                 to, and no such royalty payments shall ever become due on, any
                 Excluded Royalties.

            b.   for the Consultant and anyone who may claim through the
                 Consultant, including, but not limited to, the Consultant's
                 personal representatives, heirs, and assigns, agrees to, and
                 does hereby, irrevocably and unconditionally release and
                 forever discharge the Company and its affiliated corporations
                 of any nature, each of their agents, directors, officers,
                 employees, representatives, attorneys, predecessors,
                 successors, heirs, executors, administrators and assigns, and
                 all persons acting by, through, under or in concert with any of
                 them of and from any and all claims, assertion of claims,
                 expenses, debts, demands, actions, causes of





                                       3
<PAGE>

                 action, suits, liabilities, and/or expenses (including
                 attorneys' fees) of any nature whatsoever, whether or not now
                 known, suspected or claimed, which the Consultant ever had, now
                 has or hereafter acquires, in each case arising from any events
                 occurring before the date first written above (but not
                 thereafter), both at law and in equity ("Claims"), including,
                 but not limited to, Claims arising under or relating to (1) the
                 Consulting Agreement and the relationship and activities of the
                 parties thereunder prior to the date hereof, (2) The National
                 Labor Relations Act, as amended; (3) Title VII of the Civil
                 Rights Act of 1964, as amended; (4) Sections 1981 through 1988
                 of Title 42 of the United States Code, as amended; (5) the
                 Immigration Reform Control Act, as amended; (6) the Employee
                 Retirement Income Security Act of 1974, 29 U.S.C. Section 1001,
                 et seq., except for any claims for benefits vested, due and
                 owing; (7) the Occupational Safety and Health Act, as amended;
                 (8) the Civil Rights Act of 1866, 29 U.S.C. Section 1981, et
                 seq; (9) the Rehabilitation Act of 1973, 29 U.S.C. Section 701,
                 et seq.; (10) the Americans With Disabilities Act of 1990, as
                 amended; (11) the Civil Rights Act of 1991; (12) the Workers
                 Adjustment and Retraining Notification Act, as amended; (13)
                 Section 806 of the Corporate Fraud Accountability Act of 2002,
                 18 U.S.C. Section 1514(A); (14) the Fair Credit Reporting Act,
                 15 U.S.C. Section 1681 et. seq.; (15) the Massachusetts Law
                 Against Discrimination, G.L. c. 151B; (16) the Massachusetts
                 Wage and Hour Laws, G.L. c. 151; (17) the Massachusetts Privacy
                 Statute, G.L. c. 214, Section 1B; (18) the Massachusetts Wage
                 Payment Statute, G.L. c. 149, Section 148 et seq.; (19) the
                 Massachusetts Sexual Harassment Statute, G.L. c. 214 Section
                 1C; (20) the Massachusetts Civil Rights Act, G.L. c. 12,
                 Section 11H; (22) the Massachusetts Equal Rights Act, G.L. c.
                 93, Section 102; (23) any other federal or state law,
                 regulation, or ordinance; (24) any public policy, contract,
                 tort, or common law; (25) all claims to any non-vested
                 ownership interest in the Company, contractual or otherwise,
                 including, but not limited to, claims to stock or stock
                 options; (26) any allegation for costs, fees, or other expenses
                 including attorneys' fees incurred in these matters; (27) the
                 Excluded Royalties; and (28) any New York state law analogous
                 to, or covering any subject matter similar to, the foregoing.
                 The Consultant agrees that neither the foregoing release, nor
                 the furnishing of consideration for the foregoing release,
                 shall be deemed or construed at anytime for any purpose as an
                 admission by the Company of any liability or unlawful conduct
                 of any kind; and

            c.   except as expressly modified by this Amendment, agree and
                 reaffirm that (i) the Consulting Agreement and (ii) the
                 Approval Agreement each remain in full force and effect in
                 accordance with their terms for the full periods stated therein
                 (the "Surviving Obligations").

     3.    Release by the Company. In consideration of mutual promises contained
in this Amendment, the Company voluntarily and of its own free will for itself
and anyone who may claim through the Company or otherwise derivatively for the
Company or on its behalf, agrees to, and does hereby, irrevocably and
unconditionally release and forever discharge the





                                       4
<PAGE>


Consultant and his personal representatives, heirs and assigns from any and all
Claims the Company ever had, now has or hereafter acquires, against the
Consultant in each case arising from any events occurring before the date first
written above (but not thereafter), including, but not limited to, Claims
arising under or relating to (a) the Consulting Agreement and the relationship
and activities of the parties thereunder prior to the date hereof and (b) the
Founder Confidentiality Agreement; provided that IMI remains responsible to the
Company pursuant to the Founder Confidentiality Agreement and the assignment
thereof pursuant to Section 7.

     4.   Effect of Release on Agreements between the Company and IMI. The
Consultant and the Company expressly acknowledge and agree that (a) the Final
CDA and the License Agreement shall be unaffected by the foregoing releases and
remain in full force and effect, and (b) the releases set forth in this
Amendment shall not apply to any rights or obligations arising out of any other
agreement entered into between the Company and IMI on or after the date hereof.

     5.   Retained Rights. The Consultant and the Company expressly acknowledge
and agree that nothing contained herein shall be construed as (a) a release of
any rights or obligations of either Party arising on or after the date hereof
under the agreements set forth on Schedule A attached hereto, (b) a release of
any Claims the Consultant may have under the agreements set forth on Schedule A
regarding ownership interests in the Company or (c) an admission by either Party
of any liability to the other or unlawful conduct.

     6.   Amendment to the Approval Agreement. For the purposes of the Approval
Agreement, the Consultant and the Company hereby agree that

          a.     the phrase "physical and electrical simulation of the vagus
                 nerve" in Section 2 of the Approval Agreement shall be replaced
                 with "the Field, as defined in that certain Exclusive License
                 Agreement, dated as of January 29, 2007, by and between CRTX
                 and IMI";

          b.     the Parties hereby agree that the conditions set forth in
                 Sections 3(a)(1) and (2) of the Approval Agreement relating to
                 the share ownership of IMI and negotiation and execution of a
                 license agreement shall be fully satisfied for so long as the
                 License Agreement is in effect; and

          c.     the phrase "the one year anniversary of the Effective Date" in
                 Section 3(a)(3) of the Approval Agreement shall be replaced
                 with "June 30, 2007".

In all other respects, the Approval Agreement is hereby ratified and confirmed
and remains in full force and effect.

     7.   Relationship of the License Agreement to the Founder Confidentiality
Agreement. As expressly contemplated by the terms of the Founder Confidentiality
Agreement, the Founder Confidentiality Agreement is hereby assigned in full to
IMI, with IMI assuming all rights and obligations of the Consultant thereunder,
and the Company hereby acknowledges and consents to such assignment and releases
the Consultant in full from any of his past or future obligations under the
Founder Confidentiality Agreement.



                                       5
<PAGE>

     8.   Relationship of the Final CDA to the Original Confidentiality
Agreement and the Founder Confidentiality Agreement. As provided in paragraph 17
of the Final CDA, such agreement shall supersede each of the Original
Confidentiality Agreement and the Founder Confidentiality Agreement, with the
consequences specified therein.

     9.   Effect of Amendments. Upon the effectiveness of this Amendment, each
reference in each of the Consulting Agreement and Approval Agreement to "this
Agreement," "hereunder," "hereof," "herein" or words of like import, and each
reference in the other documents entered into in connection with the Consulting
Agreement, shall mean and be a reference to the Consulting Agreement or Approval
Agreement, as applicable, as amended hereby.

     10.  Securities Laws. The Consultant acknowledges and agrees that (i) the
Company is a publicly-held company and (ii) the Consultant is aware that
applicable securities laws prohibit any person who is aware of material,
non-public information about a publicly-held company obtained directly or
indirectly from that company from purchasing or selling securities of such
company or from communicating such information to any other person under
circumstances in which it is reasonably foreseeable that such person is likely
to purchase or sell such securities.

     11.  Governing Law. This Amendment shall be governed by, and construed in
accordance with the law of The Commonwealth of Massachusetts without regard to
any choice of law principle that would dictate the application of the law of
another jurisdiction.

     12.  Counterparts. This Amendment may be executed in counterparts, and each
such counterpart shall be deemed to be an original instrument, but all such
counterparts together shall constitute but one agreement.

        [The remainder of this page has intentionally been left blank.]



                                       6
<PAGE>


         IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the day and year first above written.

                                          CRITICAL THERAPEUTICS, INC.



                                          By:  /s/ Frank E. Thomas
                                               ---------------------------------
                                               Name: Frank E. Thomas
                                               Title: President and Chief
                                                      Executive Officer



                                          CONSULTANT:



                                          /s/ Kevin J. Tracey
                                          -------------------------------------
                                          Kevin J. Tracey, M.D.


The undersigned executes this Amendment for the sole purpose of agreeing to and
being bound by the provisions of Sections 7 and 8 hereof.


                                          INNOVATIVE METABOLICS, INC.



                                          By: /s/ Kevin J. Tracey
                                              ---------------------------------
                                              Name: Kevin J. Tracey, M.D.
                                              Title: President






<PAGE>


                                   Schedule A

1.   the Approval Agreement

2.   the Consulting Agreement

3.   the Founder Confidentiality Agreement

4.   Restricted Stock Agreement, dated July 6, 2001, by and between Critical
     Therapeutics, Inc., a Delaware corporation, and Kevin J. Tracey

5.   Restricted Stock Agreement, dated October 9, 2002, by and between Critical
     Therapeutics, Inc., a Delaware corporation, and Kevin Tracey

6.   Nonstatutory Stock Option Agreement, dated December 19, 2003, by Critical
     Therapeutics, Inc., a Delaware corporation, to Kevin J. Tracey

7.   Nonstatutory Stock Option Agreement for a Consultant, dated March 15, 2005,
     by Critical Therapeutics, Inc., a Delaware corporation, to Kevin Tracey