<PAGE>   1

      As filed with the Securities and Exchange Commission on July 18, 2000
                                                    Registration No. 333-_______

================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933


                             PAIN THERAPEUTICS, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

<TABLE>
<CAPTION>
<S>                                     <C>                                    <C>
              DELAWARE                              7841                             91-1911336
  (STATE OR OTHER JURISDICTION OF       (PRIMARY STANDARD INDUSTRIAL              (I.R.S. EMPLOYER
   INCORPORATION OR ORGANIZATION)       CLASSIFICATION CODE NUMBER)            IDENTIFICATION NUMBER)
</TABLE>

                              250 EAST GRAND AVENUE
                          SOUTH SAN FRANCISCO, CA 94080
                                 (650) 624-8200

    (ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER, INCLUDING AREA CODE,
                  OF REGISTRANT'S PRINCIPAL EXECUTIVE OFFICES)

                                 1998 STOCK PLAN
                        2000 EMPLOYEE STOCK PURCHASE PLAN
                            (FULL TITLE OF THE PLANS)

                        ---------------------------------

                                  REMI BARBIER
                             CHIEF EXECUTIVE OFFICER
                             PAIN THERAPEUTICS, INC.
                              250 EAST GRAND AVENUE
                          SOUTH SAN FRANCISCO, CA 94080
                                 (650) 624-8200


           (NAME, ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER,
                   INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                        ---------------------------------

                                   Copies to:
                           MICHAEL J . O'DONNELL, ESQ.
                             MARTIN J. WATERS, ESQ.
                        WILSON SONSINI GOODRICH & ROSATI
                            PROFESSIONAL CORPORATION
                               650 PAGE MILL ROAD
                               PALO ALTO, CA 94304
                                 (650) 493-9300

                        ---------------------------------

        APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: As soon
as practicable after the effective date of this Registration Statement.

        If any of the securities being registered on this Form are to be offered
on a delayed or continuous basis pursuant to Rule 415 under the Securities Act
of 1933, check the following box. [X]

                        ---------------------------------
================================================================================


<PAGE>   2


                               CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
=============================================================================================================
                                                            PROPOSED
                                                             MAXIMUM           PROPOSED
                                          AMOUNT            OFFERING           MAXIMUM          AMOUNT OF
TITLE OF EACH CLASS OF SECURITIES          TO BE              PRICE           AGGREGATE       REGISTRATION
         TO BE REGISTERED               REGISTERED          PER SHARE       OFFERING PRICE         FEE
-------------------------------------------------------------------------------------------------------------
<S>                                     <C>                 <C>             <C>               <C>
1998 Stock Plan
Common Stock,  $0.001 par value
(currently outstanding
options)(1) .....................        1,834,187             $1.76         $3,228,169            $852
-------------------------------------------------------------------------------------------------------------
1998 Stock Plan
Common Stock, $0.001 par value
(options available for future
grant) (2)                               1,507,634            $19.19        $28,931,496          $7,638
-------------------------------------------------------------------------------------------------------------
TOTAL 1998 STOCK PLAN SHARES
   REGISTERED                            3,341,821
-------------------------------------------------------------------------------------------------------------
2000 Employee Stock Purchase Plan
Common Stock, $0.001 par
value (3)........................          500,000            $16.31         $8,155,000          $2,153
-------------------------------------------------------------------------------------------------------------
TOTAL REGISTRATION FEES                                                                         $10,643
=============================================================================================================
</TABLE>


(1)  The computation is based upon the weighted average exercise price per share
     of $1.76 as to 1,834,187 outstanding but unexercised options to purchase
     Common Stock under the 1998 Stock Plan (the "Currently Outstanding
     Options").

(2)  The Proposed Maximum Offering Price Per Share has been estimated in
     accordance with Rule 457(h) under the Securities Act of 1933 as to the
     remaining 1,507,634 shares of Common Stock authorized for issuance pursuant
     to the 1998 Stock Plan solely for the purpose of calculating the
     registration fee. No options have been granted with respect to such shares.
     The computation is based upon the average of the high and low price of the
     Common Stock as reported on the Nasdaq National Market on July 14, 2000
     because the price at which the options to be granted in the future may be
     exercised is not currently determinable.

(3)  The Proposed Maximum Offering Price Per Share has been estimated in
     accordance with Rule 457(h) under the Securities Act of 1933 solely for the
     purpose of calculating the registration fee. The computation is based upon
     85% (see explanation in following sentence) of the average of the high and
     low price of the Common Stock as reported on the Nasdaq National Market on
     July 14, 2000 because the price at which the options to be granted in the
     future may be exercised is not currently determinable. Pursuant to the
     Employee Stock Purchase Plan, which plan is incorporated by reference
     herein, the Purchase Price of a share of Common Stock shall mean an amount
     equal to 85% of the Fair Market Value of a share of Common Stock on the
     Enrollment Date or the Exercise Date, whichever is lower.


                                      -2-
<PAGE>   3

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INFORMATION INCORPORATED BY REFERENCE.

        The following documents and information previously filed with the
Securities and Exchange Commission are hereby incorporated by reference:

        (a) The audited financial statements for the Registrant's fiscal year
            ended December 31, 1999 and the unaudited interim financial
            statements for the three (3) month period ending on March 31, 2000
            each as contained in the Prospectus, dated July 13, 2000, filed
            pursuant to Rule 424(b)(1) under the Securities Act of 1933 on July
            14, 2000.

        (b) The description of the Common Stock of the Registrant that is
            contained in the Registration Statement on Form 8-A filed pursuant
            to Section 12 of the Exchange Act on March 14, 2000.

        (c) All documents filed by the Registrant pursuant to Sections 13(a),
            13(c), 14 and 15(d) of the Exchange Act subsequent to the filing of
            this Registration Statement and prior to the filing of a
            post-effective amendment which indicates that all securities offered
            have been sold or which deregisters all securities then remaining
            unsold, shall be deemed to be incorporated by reference in the
            Registration Statement and to be part hereof from the date of filing
            of such documents.

ITEM 4. DESCRIPTION OF SECURITIES.

        Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

        Michael J. O'Donnell of Wilson Sonsini Goodrich & Rosati, Professional
Corporation, is a Director and Secretary of the Registrant. Wilson Sonsini
Goodrich & Rosati is corporate counsel to the Registrant. Individual members and
persons associated with Wilson Sonsini Goodrich & Rosati beneficially own an
aggregate of approximately 66,514 shares of the Registrant's common stock.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

        The Registrant has adopted provisions in its Certificate of
Incorporation that eliminate the personal liability of its directors and
officers for monetary damages arising from a breach of their fiduciary duties in
certain circumstances to the fullest extent permitted by law and authorizes the
Registrant to indemnify its directors and officers to the fullest extent
permitted by law. Such limitation of liability does not affect the availability
of equitable remedies such as injunctive relief or rescission.

        The Registrant's Bylaws provide that the Registrant shall indemnify its
directors and officers to the fullest extent permitted by the General
Corporation Law of Delaware, including circumstances in which indemnification is
otherwise discretionary under Delaware law. Section 145 of the General
Corporation Law of Delaware provides for the indemnification of officers,
directors and other corporate agents in terms sufficiently broad to indemnify
such persons, under certain circumstances, for certain liabilities (including
reimbursement of expenses incurred) arising under the Securities Act of 1933
(the "Securities Act"). The Registrant has entered into indemnification
agreements to such effect with its officers and directors containing provisions
which are in some respects broader than the specific indemnification provisions
contained in the General Corporation Law of Delaware. The indemnification
agreements may require the Company, among other things, to indemnify such
officers and directors against certain liabilities that may arise by reason of
their status or service as directors or officers (other than liabilities arising
from willful misconduct of a


                                      II-1
<PAGE>   4

culpable nature) and to advance their expenses incurred as a result of any
proceeding against them as to which they could be indemnified.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

        Not applicable.

ITEM 8. EXHIBITS.

        The Exhibits listed on the accompanying Index to Exhibits are filed as
part hereof, or incorporated by reference into, this Registration Statement.
(See Exhibit Index below).

ITEM 9. UNDERTAKINGS.

        (a) The undersigned Registrant hereby undertakes:

            (1) To file, during any period in which offers or sales are being
made, a post-effective amendment to this Registration Statement to include any
material information with respect to the plan of distribution not previously
disclosed in the Registration Statement or any material change to such
information in the Registration Statement.

            (2) That, for the purpose of determining any liability under the
Securities Act, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

            (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

        (b) The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be an initial bona fide offering thereof.

        (c) Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions, or otherwise,
the Registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Securities Act and is, therefore, unenforceable. In the event that a
claim for indemnification against such liabilities (other than the payment by
the Registrant of expenses incurred or paid by a director, officer or
controlling person of the Registrant in the successful defense of any action,
suit or proceeding) is asserted by such director, officer or controlling person
in connection with the securities being registered, the Registrant will, unless
in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the Act and
will be governed by the final adjudication of such issue.


                                      II-2
<PAGE>   5

                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized in the City of South San Francisco, State of California on July 18,
2000.


                                       PAIN THERAPEUTICS, INC.


                                       By: /s/ Remi Barbier
                                           -------------------------------------
                                           Remi Barbier
                                           President and Chief Executive Officer


                                      II-3
<PAGE>   6

                                POWER OF ATTORNEY

        KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Remi Barbier and David Johnson, jointly
and severally, his or her attorneys-in-fact, each with the power of
substitution, for him or her in any and all capacities, to sign any amendments
to this Registration Statement on Form S-8, and to file the same, with exhibits
thereto and other documents in connection therewith, with the Securities and
Exchange Commission, hereby ratifying and confirming all that each of said
attorneys-in-fact, or his substitute or substitutes, may do or cause to be done
by virtue hereof.

        Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the date indicated.

<TABLE>
<CAPTION>
                 SIGNATURE                               TITLE                           DATE
                 ---------                               -----                           ----
<S>                                           <C>                                    <C>
 /s/ Remi Barbier                             President, Chief Executive             July 18, 2000
------------------------------------          Officer and Director (Principal
                Remi Barbier                  Executive Officer)


/s/ David Johnson                             Chief Financial Officer                July 18, 2000
------------------------------------          (Principal Financial and
               David Johnson                  Accounting Officer)


/s/ Gert Caspritz                             Director                               July 18, 2000
------------------------------------
            Gert Caspritz, Ph.D.


/s/ Nadav Friedmann                           Director                               July 18, 2000
------------------------------------
        Nadav Friedmann, M.D., Ph.D.


/s/ Wilfred Konneker                          Director                               July 18, 2000
------------------------------------
          Wilfred Konneker, Ph.D.


/s/ Michael J. O'Donnell                      Director                               July 18, 2000
------------------------------------
            Michael J. O'Donnell


/s/ Sanford R. Robertson                      Director                               July 18, 2000
------------------------------------
            Sanford R. Robertson
</TABLE>


*    The employee benefit plans being registered pursuant to this Registration
     Statement are subject to administration by the Board of Directors of the
     Registrant.


                                      II-4
<PAGE>   7

                                INDEX TO EXHIBITS



<TABLE>
<CAPTION>
                                                                                      SEQUENTIALLY
    EXHIBIT NUMBER                         EXHIBIT DOCUMENT                           NUMBERED PAGE
    -----------------------------------------------------------------------------------------------
<S>                 <C>                                                               <C>
          3.1*      Certificate of Incorporation of Registrant

          3.2*      Bylaws of Registrant

         10.5*      1998 Stock Plan

         10.6*      2000 Employee Stock Purchase Plan

          5.1       Opinion of Wilson Sonsini Goodrich & Rosati, Professional
                    Corporation, as to the legality of securities being
                    registered (Counsel to the Registrant)

         23.1       Consent of KPMG LLP Independent Certified Public Accountants

         23.2       Consent of Wilson Sonsini Goodrich & Rosati, Professional
                    Corporation (contained in Exhibit 5.1 hereto)

         24.1       Power of Attorney (see page II-5)
</TABLE>

---------------
*    Incorporated by reference to the Company's Registration Statement on Form
     S-1 (File No. 333-32370), effective July 13, 2000.
[{"type": "S-8", "sequence": "1", "filename": "s-8.txt", "description": "FORM S-8", "secsgml_size_bytes": 18978}]
{"company-data": {"conformed-name": "PAIN THERAPEUTICS INC", "cik": "0001069530", "assigned-sic": "2834", "irs-number": "911911336", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-41660", "film-number": "674758"}, "business-address": {"street1": "250 EAST GRAND AVENUE", "street2": "SUITE 70", "city": "SOUTH SAN FRANCISCO", "state": "CA", "zip": "94080", "phone": "6506248200"}, "mail-address": {"street1": "250 EAST GRAND AVENUE", "street2": "SUITE 70", "city": "SOUTH SAN FRANCISCO", "state": "CA", "zip": "94080"}}
1

      As filed with the Securities and Exchange Commission on July 18, 2000
                                                    Registration No. 333-_______

================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                             PAIN THERAPEUTICS, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
DELAWARE                              7841                             91-1911336
  (STATE OR OTHER JURISDICTION OF       (PRIMARY STANDARD INDUSTRIAL              (I.R.S. EMPLOYER
   INCORPORATION OR ORGANIZATION)       CLASSIFICATION CODE NUMBER)            IDENTIFICATION NUMBER)
250 EAST GRAND AVENUE
                          SOUTH SAN FRANCISCO, CA 94080
                                 (650) 624-8200

    (ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER, INCLUDING AREA CODE,
                  OF REGISTRANT'S PRINCIPAL EXECUTIVE OFFICES)

                                 1998 STOCK PLAN
                        2000 EMPLOYEE STOCK PURCHASE PLAN
                            (FULL TITLE OF THE PLANS)

                        ---------------------------------

                                  REMI BARBIER
                             CHIEF EXECUTIVE OFFICER
                             PAIN THERAPEUTICS, INC.
                              250 EAST GRAND AVENUE
                          SOUTH SAN FRANCISCO, CA 94080
                                 (650) 624-8200

           (NAME, ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER,
                   INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                        ---------------------------------

                                   Copies to:
                           MICHAEL J . O'DONNELL, ESQ.
                             MARTIN J. WATERS, ESQ.
                        WILSON SONSINI GOODRICH & ROSATI
                            PROFESSIONAL CORPORATION
                               650 PAGE MILL ROAD
                               PALO ALTO, CA 94304
                                 (650) 493-9300

                        ---------------------------------

        APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: As soon
as practicable after the effective date of this Registration Statement.

        If any of the securities being registered on this Form are to be offered
on a delayed or continuous basis pursuant to Rule 415 under the Securities Act
of 1933, check the following box. [X]

                        ---------------------------------
================================================================================
2

                               CALCULATION OF REGISTRATION FEE
=============================================================================================================
                                                            PROPOSED
                                                             MAXIMUM           PROPOSED
                                          AMOUNT            OFFERING           MAXIMUM          AMOUNT OF
TITLE OF EACH CLASS OF SECURITIES          TO BE              PRICE           AGGREGATE       REGISTRATION
         TO BE REGISTERED               REGISTERED          PER SHARE       OFFERING PRICE         FEE
-------------------------------------------------------------------------------------------------------------
1998 Stock Plan
Common Stock,  $0.001 par value
(currently outstanding
options)(1) .....................        1,834,187             $1.76         $3,228,169            $852
-------------------------------------------------------------------------------------------------------------
1998 Stock Plan
Common Stock, $0.001 par value
(options available for future
grant) (2)                               1,507,634            $19.19        $28,931,496          $7,638
-------------------------------------------------------------------------------------------------------------
TOTAL 1998 STOCK PLAN SHARES
   REGISTERED                            3,341,821
-------------------------------------------------------------------------------------------------------------
2000 Employee Stock Purchase Plan
Common Stock, $0.001 par
value (3)........................          500,000            $16.31         $8,155,000          $2,153
-------------------------------------------------------------------------------------------------------------
TOTAL REGISTRATION FEES                                                                         $10,643
=============================================================================================================
(1)  The computation is based upon the weighted average exercise price per share
     of $1.76 as to 1,834,187 outstanding but unexercised options to purchase
     Common Stock under the 1998 Stock Plan (the "Currently Outstanding
     Options").

(2)  The Proposed Maximum Offering Price Per Share has been estimated in
     accordance with Rule 457(h) under the Securities Act of 1933 as to the
     remaining 1,507,634 shares of Common Stock authorized for issuance pursuant
     to the 1998 Stock Plan solely for the purpose of calculating the
     registration fee. No options have been granted with respect to such shares.
     The computation is based upon the average of the high and low price of the
     Common Stock as reported on the Nasdaq National Market on July 14, 2000
     because the price at which the options to be granted in the future may be
     exercised is not currently determinable.

(3)  The Proposed Maximum Offering Price Per Share has been estimated in
     accordance with Rule 457(h) under the Securities Act of 1933 solely for the
     purpose of calculating the registration fee. The computation is based upon
     85% (see explanation in following sentence) of the average of the high and
     low price of the Common Stock as reported on the Nasdaq National Market on
     July 14, 2000 because the price at which the options to be granted in the
     future may be exercised is not currently determinable. Pursuant to the
     Employee Stock Purchase Plan, which plan is incorporated by reference
     herein, the Purchase Price of a share of Common Stock shall mean an amount
     equal to 85% of the Fair Market Value of a share of Common Stock on the
     Enrollment Date or the Exercise Date, whichever is lower.

                                      -2-
3

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INFORMATION INCORPORATED BY REFERENCE.

        The following documents and information previously filed with the
Securities and Exchange Commission are hereby incorporated by reference:

        (a) The audited financial statements for the Registrant's fiscal year
            ended December 31, 1999 and the unaudited interim financial
            statements for the three (3) month period ending on March 31, 2000
            each as contained in the Prospectus, dated July 13, 2000, filed
            pursuant to Rule 424(b)(1) under the Securities Act of 1933 on July
            14, 2000.

        (b) The description of the Common Stock of the Registrant that is
            contained in the Registration Statement on Form 8-A filed pursuant
            to Section 12 of the Exchange Act on March 14, 2000.

        (c) All documents filed by the Registrant pursuant to Sections 13(a),
            13(c), 14 and 15(d) of the Exchange Act subsequent to the filing of
            this Registration Statement and prior to the filing of a
            post-effective amendment which indicates that all securities offered
            have been sold or which deregisters all securities then remaining
            unsold, shall be deemed to be incorporated by reference in the
            Registration Statement and to be part hereof from the date of filing
            of such documents.

ITEM 4. DESCRIPTION OF SECURITIES.

        Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

        Michael J. O'Donnell of Wilson Sonsini Goodrich & Rosati, Professional
Corporation, is a Director and Secretary of the Registrant. Wilson Sonsini
Goodrich & Rosati is corporate counsel to the Registrant. Individual members and
persons associated with Wilson Sonsini Goodrich & Rosati beneficially own an
aggregate of approximately 66,514 shares of the Registrant's common stock.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

        The Registrant has adopted provisions in its Certificate of
Incorporation that eliminate the personal liability of its directors and
officers for monetary damages arising from a breach of their fiduciary duties in
certain circumstances to the fullest extent permitted by law and authorizes the
Registrant to indemnify its directors and officers to the fullest extent
permitted by law. Such limitation of liability does not affect the availability
of equitable remedies such as injunctive relief or rescission.

        The Registrant's Bylaws provide that the Registrant shall indemnify its
directors and officers to the fullest extent permitted by the General
Corporation Law of Delaware, including circumstances in which indemnification is
otherwise discretionary under Delaware law. Section 145 of the General
Corporation Law of Delaware provides for the indemnification of officers,
directors and other corporate agents in terms sufficiently broad to indemnify
such persons, under certain circumstances, for certain liabilities (including
reimbursement of expenses incurred) arising under the Securities Act of 1933
(the "Securities Act"). The Registrant has entered into indemnification
agreements to such effect with its officers and directors containing provisions
which are in some respects broader than the specific indemnification provisions
contained in the General Corporation Law of Delaware. The indemnification
agreements may require the Company, among other things, to indemnify such
officers and directors against certain liabilities that may arise by reason of
their status or service as directors or officers (other than liabilities arising
from willful misconduct of a

                                      II-1
4

culpable nature) and to advance their expenses incurred as a result of any
proceeding against them as to which they could be indemnified.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

        Not applicable.

ITEM 8. EXHIBITS.

        The Exhibits listed on the accompanying Index to Exhibits are filed as
part hereof, or incorporated by reference into, this Registration Statement.
(See Exhibit Index below).

ITEM 9. UNDERTAKINGS.

        (a) The undersigned Registrant hereby undertakes:

            (1) To file, during any period in which offers or sales are being
made, a post-effective amendment to this Registration Statement to include any
material information with respect to the plan of distribution not previously
disclosed in the Registration Statement or any material change to such
information in the Registration Statement.

            (2) That, for the purpose of determining any liability under the
Securities Act, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

            (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

        (b) The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be an initial bona fide offering thereof.

        (c) Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions, or otherwise,
the Registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Securities Act and is, therefore, unenforceable. In the event that a
claim for indemnification against such liabilities (other than the payment by
the Registrant of expenses incurred or paid by a director, officer or
controlling person of the Registrant in the successful defense of any action,
suit or proceeding) is asserted by such director, officer or controlling person
in connection with the securities being registered, the Registrant will, unless
in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the Act and
will be governed by the final adjudication of such issue.

                                      II-2
5

                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized in the City of South San Francisco, State of California on July 18,
2000.

                                       PAIN THERAPEUTICS, INC.

                                       By: /s/ Remi Barbier
                                           -------------------------------------
                                           Remi Barbier
                                           President and Chief Executive Officer

                                      II-3
6

                                POWER OF ATTORNEY

        KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Remi Barbier and David Johnson, jointly
and severally, his or her attorneys-in-fact, each with the power of
substitution, for him or her in any and all capacities, to sign any amendments
to this Registration Statement on Form S-8, and to file the same, with exhibits
thereto and other documents in connection therewith, with the Securities and
Exchange Commission, hereby ratifying and confirming all that each of said
attorneys-in-fact, or his substitute or substitutes, may do or cause to be done
by virtue hereof.

        Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the date indicated.
SIGNATURE                               TITLE                           DATE
                 ---------                               -----                           ----
/s/ Remi Barbier                             President, Chief Executive             July 18, 2000
------------------------------------          Officer and Director (Principal
                Remi Barbier                  Executive Officer)

/s/ David Johnson                             Chief Financial Officer                July 18, 2000
------------------------------------          (Principal Financial and
               David Johnson                  Accounting Officer)

/s/ Gert Caspritz                             Director                               July 18, 2000
------------------------------------
            Gert Caspritz, Ph.D.

/s/ Nadav Friedmann                           Director                               July 18, 2000
------------------------------------
        Nadav Friedmann, M.D., Ph.D.

/s/ Wilfred Konneker                          Director                               July 18, 2000
------------------------------------
          Wilfred Konneker, Ph.D.

/s/ Michael J. O'Donnell                      Director                               July 18, 2000
------------------------------------
            Michael J. O'Donnell

/s/ Sanford R. Robertson                      Director                               July 18, 2000
------------------------------------
            Sanford R. Robertson
*    The employee benefit plans being registered pursuant to this Registration
     Statement are subject to administration by the Board of Directors of the
     Registrant.

                                      II-4
7

                                INDEX TO EXHIBITS
SEQUENTIALLY
    EXHIBIT NUMBER                         EXHIBIT DOCUMENT                           NUMBERED PAGE
    -----------------------------------------------------------------------------------------------
3.1*      Certificate of Incorporation of Registrant

          3.2*      Bylaws of Registrant

         10.5*      1998 Stock Plan

         10.6*      2000 Employee Stock Purchase Plan

          5.1       Opinion of Wilson Sonsini Goodrich & Rosati, Professional
                    Corporation, as to the legality of securities being
                    registered (Counsel to the Registrant)

         23.1       Consent of KPMG LLP Independent Certified Public Accountants

         23.2       Consent of Wilson Sonsini Goodrich & Rosati, Professional
                    Corporation (contained in Exhibit 5.1 hereto)

         24.1       Power of Attorney (see page II-5)
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*    Incorporated by reference to the Company's Registration Statement on Form
     S-1 (File No. 333-32370), effective July 13, 2000.