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                                                                    EXHIBIT 10.6

                             PAIN THERAPEUTICS, INC.


                        2000 EMPLOYEE STOCK PURCHASE PLAN


        The following constitute the provisions of the 2000 Employee Stock
Purchase Plan of Pain Therapeutics, Inc.

        1. Purpose. The purpose of the Plan is to provide employees of the
Company and its Designated Subsidiaries with an opportunity to purchase Common
Stock of the Company through accumulated payroll deductions. It is the intention
of the Company to have the Plan qualify as an "Employee Stock Purchase Plan"
under Section 423 of the Internal Revenue Code of 1986, as amended. The
provisions of the Plan, accordingly, shall be construed so as to extend and
limit participation in a manner consistent with the requirements of that section
of the Code.

        2. Definitions.

               (a) "Board" shall mean the Board of Directors of the Company or
any committee thereof designated by the Board of Directors of the Company in
accordance with Section 14 of the Plan.

               (b) "Code" shall mean the Internal Revenue Code of 1986, as
amended.

               (c) "Common Stock" shall mean the common stock of the Company.

               (d) "Company" shall mean Pain Therapeutics, Inc., a Delaware
Corporation and any Designated Subsidiary of the Company.

               (e) "Compensation" shall mean all base straight time gross
earnings but exclusive of payments for commissions, overtime, shift premium,
incentive compensation, incentive payments, bonuses and other compensation.

               (f) "Designated Subsidiary" shall mean any Subsidiary that has
been designated by the Board from time to time in its sole discretion as
eligible to participate in the Plan.

               (g) "Employee" shall mean any individual who is an Employee of
the Company for tax purposes whose customary employment with the Company is at
least twenty (20) hours per week and more than five (5) months in any calendar
year. For purposes of the Plan, the employment relationship shall be treated as
continuing intact while the individual is on sick leave or other leave of
absence approved by the Company. Where the period of leave exceeds 90 days and
the individual's right to reemployment is not guaranteed either by statute or by
contract, the employment relationship shall be deemed to have terminated on the
91st day of such leave.

               (h) "Enrollment Date" shall mean the first Trading Day of each
Offering Period.



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               (i) "Exercise Date" shall mean the first Trading Day on or after
MAY 1ST AND NOVEMBER 1ST of each year.

               (j) "Fair Market Value" shall mean, as of any date, the value of
Common Stock determined as follows:

                          (i) If the Common Stock is listed on any established
stock exchange or a national market system, including without limitation the
Nasdaq National Market or The Nasdaq SmallCap Market of The Nasdaq Stock Market,
its Fair Market Value shall be the closing sales price for such stock (or the
closing bid, if no sales were reported) as quoted on such exchange or system on
the date of determination, as reported in The Wall Street Journal or such other
source as the Board deems reliable;

                          (ii) If the Common Stock is regularly quoted by a
recognized securities dealer but selling prices are not reported, its Fair
Market Value shall be the mean of the closing bid and asked prices for the
Common Stock on the date of determination, as reported in The Wall Street
Journal or such other source as the Board deems reliable;

                          (iii) In the absence of an established market for the
Common Stock, the Fair Market Value thereof shall be determined in good faith by
the Board; or

                          (iv) For purposes of the Enrollment Date of the first
Offering Period under the Plan, the Fair Market Value shall be the initial price
to the public as set forth in the final prospectus included within the
registration statement in Form S-1 filed with the Securities and Exchange
Commission for the initial public offering of the Company's Common Stock (the
"Registration Statement").

               (k) "Offering Periods" shall mean the periods of approximately
twenty-four (24) months during which an option granted pursuant to the Plan may
be exercised, commencing on the first Trading Day on or after MAY 1ST AND
NOVEMBER 1ST of each year and terminating on the first Trading Day on or after
the MAY 1ST AND NOVEMBER 1ST Offering Period commencement date approximately
twenty-four months later; provided, however, that the first Offering Period
under the Plan shall commence with the first Trading Day on or after the date on
which the Securities and Exchange Commission declares the Company's Registration
Statement effective and ending on the first Trading Day on or after MAY 1, 2002.
The duration and timing of Offering Periods may be changed pursuant to Section 4
of this Plan.

               (l) "Plan" shall mean this 2000 Employee Stock Purchase Plan.

               (m) "Purchase Period" shall mean the approximately six month
period commencing on one Exercise Date and ending with the next Exercise Date,
except that the first Purchase Period of any Offering Period shall commence on
the Enrollment Date and end with the next Exercise Date.

               (n) "Purchase Price" shall mean 85% of the Fair Market Value of a
share of Common Stock on the Enrollment Date or on the Exercise Date, whichever
is lower; provided however, that the Purchase Price may be adjusted by the Board
pursuant to Section 20.

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               (o) "Reserves" shall mean the number of shares of Common Stock
covered by each option under the Plan which have not yet been exercised and the
number of shares of Common Stock which have been authorized for issuance under
the Plan but not yet placed under option.

               (p) "Subsidiary" shall mean a corporation, domestic or foreign,
of which not less than 50% of the voting shares are held by the Company or a
Subsidiary, whether or not such corporation now exists or is hereafter organized
or acquired by the Company or a Subsidiary.

               (q) "Trading Day" shall mean a day on which national stock
exchanges and the Nasdaq System are open for trading.

        3. Eligibility.

               (a) Any Employee who shall be employed by the Company on a given
Enrollment Date shall be eligible to participate in the Plan.

               (b) Any provisions of the Plan to the contrary notwithstanding,
no Employee shall be granted an option under the Plan (i) to the extent that,
immediately after the grant, such Employee (or any other person whose stock
would be attributed to such Employee pursuant to Section 424(d) of the Code)
would own capital stock of the Company and/or hold outstanding options to
purchase such stock possessing five percent (5%) or more of the total combined
voting power or value of all classes of the capital stock of the Company or of
any Subsidiary, or (ii) to the extent that his or her rights to purchase stock
under all employee stock purchase plans of the Company and its subsidiaries
accrues at a rate which exceeds Twenty-Five Thousand Dollars ($25,000) worth of
stock (determined at the fair market value of the shares at the time such option
is granted) for each calendar year in which such option is outstanding at any
time.

        4. Offering Periods. The Plan shall be implemented by consecutive,
overlapping Offering Periods with a new Offering Period commencing on the first
Trading Day on or after MAY 1ST AND NOVEMBER 1ST each year, or on such other
date as the Board shall determine, and continuing thereafter until terminated in
accordance with Section 20 hereof; provided, however, that the first Offering
Period under the Plan shall commence with the first Trading Day on or after the
date on which the Securities and Exchange Commission declares the Company's
Registration Statement effective and ending on the first Trading Day on or after
[MAY 1, 2002.] The Board shall have the power to change the duration of Offering
Periods (including the commencement dates thereof) with respect to future
offerings without stockholder approval if such change is announced at least five
(5) days prior to the scheduled beginning of the first Offering Period to be
affected thereafter.

        5. Participation.

               (a) An eligible Employee may become a participant in the Plan by
completing a subscription agreement authorizing payroll deductions in the form
of Exhibit A to this Plan and filing it with the Company's payroll office prior
to the applicable Enrollment Date.

               (b) Payroll deductions for a participant shall commence on the
first payroll following the Enrollment Date and shall end on the last payroll in
the Offering Period to which such authorization is applicable, unless sooner
terminated by the participant as provided in Section 10 hereof.

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        6. Payroll Deductions.

               (a) At the time a participant files his or her subscription
agreement, he or she shall elect to have payroll deductions made on each pay day
during the Offering Period in an amount not exceeding fifteen percent (15%) of
the Compensation which he or she receives on each pay day during the Offering
Period; provided, however, that should a pay day occur on an Exercise Date, a
participant shall have the payroll deductions made on such day applied to his or
her account under the new Offering Period or Purchase Period, as the case may
be.

               (b) All payroll deductions made for a participant shall be
credited to his or her account under the Plan and shall be withheld in whole
percentages only. A participant may not make any additional payments into such
account.

               (c) A participant may discontinue his or her participation in the
Plan as provided in Section 10 hereof, or may increase or decrease the rate of
his or her payroll deductions during the Offering Period by completing or filing
with the Company a new subscription agreement authorizing a change in payroll
deduction rate. The Company may, in its discretion, limit the nature and/or
number of participation rate changes during any Offering Period, and may
establish such other conditions or limitations as it deems appropriate for Plan
administration. The change in rate shall be effective with the first full
payroll period following five (5) business days after the Company's receipt of
the new subscription agreement unless the Company elects to process a given
change in participation more quickly. A participant's subscription agreement
shall remain in effect for successive Offering Periods unless terminated as
provided in Section 10 hereof.

               (d) Notwithstanding the foregoing, to the extent necessary to
comply with Section 423(b)(8) of the Code and Section 3(b) hereof, a
participant's payroll deductions may be decreased to zero percent (0%) at any
time during a Purchase Period. Payroll deductions shall recommence at the rate
provided in such participant's subscription agreement at the beginning of the
first Purchase Period which is scheduled to end in the following calendar year,
unless terminated by the participant as provided in Section 10 hereof.

               (e) At the time the option is exercised, in whole or in part, or
at the time some or all of the Company's Common Stock issued under the Plan is
disposed of, the participant must make adequate provision for the Company's
federal, state, or other tax withholding obligations, if any, which arise upon
the exercise of the option or the disposition of the Common Stock. At any time,
the Company may, but shall not be obligated to, withhold from the participant's
compensation the amount necessary for the Company to meet applicable withholding
obligations, including any withholding required to make available to the Company
any tax deductions or benefits attributable to sale or early disposition of
Common Stock by the Employee.

        7. Grant of Option. On the Enrollment Date of each Offering Period, each
eligible Employee participating in such Offering Period shall be granted an
option to purchase on each Exercise Date during such Offering Period (at the
applicable Purchase Price) up to a number of shares of the Company's Common
Stock determined by dividing such Employee's payroll deductions accumulated
prior to such Exercise Date and retained in the Participant's account as of the
Exercise Date by the applicable Purchase Price; provided that in no event shall
an Employee be permitted to purchase during each Purchase Period more than 7,500
shares of the Company's Common Stock

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(subject to any adjustment pursuant to Section 19), and provided further that
such purchase shall be subject to the limitations set forth in Sections 3(b) and
12 hereof. The Board may, for future Offering Periods, increase or decrease, in
its absolute discretion, the maximum number of shares of the Company's Common
Stock an Employee may purchase during each Purchase Period of such Offering
Period. Exercise of the option shall occur as provided in Section 8 hereof,
unless the participant has withdrawn pursuant to Section 10 hereof. The option
shall expire on the last day of the Offering Period.

        8. Exercise of Option.

               (a) Unless a participant withdraws from the Plan as provided in
Section 10 hereof, his or her option for the purchase of shares shall be
exercised automatically on the Exercise Date, and the maximum number of full
shares subject to option shall be purchased for such participant at the
applicable Purchase Price with the accumulated payroll deductions in his or her
account. No fractional shares shall be purchased; any payroll deductions
accumulated in a participant's account which are not sufficient to purchase a
full share shall be retained in the participant's account for the subsequent
Purchase Period or Offering Period, subject to earlier withdrawal by the
participant as provided in Section 10 hereof. Any other monies left over in a
participant's account after the Exercise Date shall be returned to the
participant. During a participant's lifetime, a participant's option to purchase
shares hereunder is exercisable only by him or her.

               (b) If the Board determines that, on a given Exercise Date, the
number of shares with respect to which options are to be exercised may exceed
(i) the number of shares of Common Stock that were available for sale under the
Plan on the Enrollment Date of the applicable Offering Period, or (ii) the
number of shares available for sale under the Plan on such Exercise Date, the
Board may in its sole discretion (x) provide that the Company shall make a pro
rata allocation of the shares of Common Stock available for purchase on such
Enrollment Date or Exercise Date, as applicable, in as uniform a manner as shall
be practicable and as it shall determine in its sole discretion to be equitable
among all participants exercising options to purchase Common Stock on such
Exercise Date, and continue all Offering Periods then in effect, or (y) provide
that the Company shall make a pro rata allocation of the shares available for
purchase on such Enrollment Date or Exercise Date, as applicable, in as uniform
a manner as shall be practicable and as it shall determine in its sole
discretion to be equitable among all participants exercising options to purchase
Common Stock on such Exercise Date, and terminate any or all Offering Periods
then in effect pursuant to Section 20 hereof. The Company may make pro rata
allocation of the shares available on the Enrollment Date of any applicable
Offering Period pursuant to the preceding sentence, notwithstanding any
authorization of additional shares for issuance under the Plan by the Company's
stockholders subsequent to such Enrollment Date.

        9. Delivery. As promptly as practicable after each Exercise Date on
which a purchase of shares occurs, the Company shall arrange the delivery to
each participant, as appropriate, of a certificate representing the shares
purchased upon exercise of his or her option.

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        10. Withdrawal.

               (a) A participant may withdraw all but not less than all the
payroll deductions credited to his or her account and not yet used to exercise
his or her option under the Plan at any time by giving written notice to the
Company in the form of Exhibit B to this Plan. All of the participant's payroll
deductions credited to his or her account shall be paid to such participant
promptly after receipt of notice of withdrawal and such participant's option for
the Offering Period shall be automatically terminated, and no further payroll
deductions for the purchase of shares shall be made for such Offering Period. If
a participant withdraws from an Offering Period, payroll deductions shall not
resume at the beginning of the succeeding Offering Period unless the participant
delivers to the Company a new subscription agreement.

               (b) A participant's withdrawal from an Offering Period shall not
have any effect upon his or her eligibility to participate in any similar plan
which may hereafter be adopted by the Company or in succeeding Offering Periods
which commence after the termination of the Offering Period from which the
participant withdraws.

        11. Termination of Employment.

               Upon a participant's ceasing to be an Employee, for any reason,
he or she shall be deemed to have elected to withdraw from the Plan and the
payroll deductions credited to such participant's account during the Offering
Period but not yet used to exercise the option shall be returned to such
participant or, in the case of his or her death, to the person or persons
entitled thereto under Section 15 hereof, and such participant's option shall be
automatically terminated. The preceding sentence notwithstanding, a participant
who receives payment in lieu of notice of termination of employment shall be
treated as continuing to be an Employee for the participant's customary number
of hours per week of employment during the period in which the participant is
subject to such payment in lieu of notice.

        12. Interest. No interest shall accrue on the payroll deductions of a
participant in the Plan.

        13. Stock.

               (a) Subject to adjustment upon changes in capitalization of the
Company as provided in Section 19 hereof, the maximum number of shares of the
Company's Common Stock which shall be made available for sale under the Plan
shall be 500,000 shares, plus an annual increase to be added on the first day of
the Company's fiscal year, beginning in 2001, equal to the lesser of (i) 500,000
shares, (ii) 1% of the outstanding shares of Common Stock on such date, or (iii)
an amount determined by the Board.

               (b) The participant shall have no interest or voting right in
shares covered by his option until such option has been exercised.

               (c) Shares to be delivered to a participant under the Plan shall
be registered in the name of the participant or in the name of the participant
and his or her spouse.

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        14. Administration. The Plan shall be administered by the Board or a
committee of members of the Board appointed by the Board. The Board or its
committee shall have full and exclusive discretionary authority to construe,
interpret and apply the terms of the Plan, to determine eligibility and to
adjudicate all disputed claims filed under the Plan. Every finding, decision and
determination made by the Board or its committee shall, to the full extent
permitted by law, be final and binding upon all parties.

        15. Designation of Beneficiary.

               (a) A participant may file a written designation of a beneficiary
who is to receive any shares and cash, if any, from the participant's account
under the Plan in the event of such participant's death subsequent to an
Exercise Date on which the option is exercised but prior to delivery to such
participant of such shares and cash. In addition, a participant may file a
written designation of a beneficiary who is to receive any cash from the
participant's account under the Plan in the event of such participant's death
prior to exercise of the option. If a participant is married and the designated
beneficiary is not the spouse, spousal consent shall be required for such
designation to be effective.

               (b) Such designation of beneficiary may be changed by the
participant at any time by written notice. In the event of the death of a
participant and in the absence of a beneficiary validly designated under the
Plan who is living at the time of such participant's death, the Company shall
deliver such shares and/or cash to the executor or administrator of the estate
of the participant, or if no such executor or administrator has been appointed
(to the knowledge of the Company), the Company, in its discretion, may deliver
such shares and/or cash to the spouse or to any one or more dependents or
relatives of the participant, or if no spouse, dependent or relative is known to
the Company, then to such other person as the Company may designate.

        16. Transferability. Neither payroll deductions credited to a
participant's account nor any rights with regard to the exercise of an option or
to receive shares under the Plan may be assigned, transferred, pledged or
otherwise disposed of in any way (other than by will, the laws of descent and
distribution or as provided in Section 15 hereof) by the participant. Any such
attempt at assignment, transfer, pledge or other disposition shall be without
effect, except that the Company may treat such act as an election to withdraw
funds from an Offering Period in accordance with Section 10 hereof.

        17. Use of Funds. All payroll deductions received or held by the Company
under the Plan may be used by the Company for any corporate purpose, and the
Company shall not be obligated to segregate such payroll deductions.

        18. Reports. Individual accounts shall be maintained for each
participant in the Plan. Statements of account shall be given to participating
Employees at least annually, which statements shall set forth the amounts of
payroll deductions, the Purchase Price, the number of shares purchased and the
remaining cash balance, if any.

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        19. Adjustments Upon Changes in Capitalization, Dissolution,
            Liquidation, Merger or Asset Sale.

               (a) Changes in Capitalization. Subject to any required action by
the stockholders of the Company, the Reserves (including the number of shares
automatically added annually to the Plan pursuant to Section 13(a)(i)), the
maximum number of shares each participant may purchase each Purchase Period
(pursuant to Section 7), as well as the price per share and the number of shares
of Common Stock covered by each option under the Plan which has not yet been
exercised shall be proportionately adjusted for any increase or decrease in the
number of issued shares of Common Stock resulting from a stock split, reverse
stock split, stock dividend, combination or reclassification of the Common
Stock, or any other increase or decrease in the number of shares of Common Stock
effected without receipt of consideration by the Company; provided, however,
that conversion of any convertible securities of the Company shall not be deemed
to have been "effected without receipt of consideration." Such adjustment shall
be made by the Board, whose determination in that respect shall be final,
binding and conclusive. Except as expressly provided herein, no issuance by the
Company of shares of stock of any class, or securities convertible into shares
of stock of any class, shall affect, and no adjustment by reason thereof shall
be made with respect to, the number or price of shares of Common Stock subject
to an option.

               (b) Dissolution or Liquidation. In the event of the proposed
dissolution or liquidation of the Company, the Offering Period then in progress
shall be shortened by setting a new Exercise Date (the "New Exercise Date"), and
shall terminate immediately prior to the consummation of such proposed
dissolution or liquidation, unless provided otherwise by the Board. The New
Exercise Date shall be before the date of the Company's proposed dissolution or
liquidation. The Board shall notify each participant in writing, at least ten
(10) business days prior to the New Exercise Date, that the Exercise Date for
the participant's option has been changed to the New Exercise Date and that the
participant's option shall be exercised automatically on the New Exercise Date,
unless prior to such date the participant has withdrawn from the Offering Period
as provided in Section 10 hereof.

               (c) Merger or Asset Sale. In the event of a proposed sale of all
or substantially all of the assets of the Company, or the merger of the Company
with or into another corporation, each outstanding option shall be assumed or an
equivalent option substituted by the successor corporation or a Parent or
Subsidiary of the successor corporation. In the event that the successor
corporation refuses to assume or substitute for the option, any Purchase Periods
then in progress shall be shortened by setting a new Exercise Date (the "New
Exercise Date") and any Offering Periods then in progress shall end on the New
Exercise Date. The New Exercise Date shall be before the date of the Company's
proposed sale or merger. The Board shall notify each participant in writing, at
least ten (10) business days prior to the New Exercise Date, that the Exercise
Date for the participant's option has been changed to the New Exercise Date and
that the participant's option shall be exercised automatically on the New
Exercise Date, unless prior to such date the participant has withdrawn from the
Offering Period as provided in Section 10 hereof.

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        20. Amendment or Termination.

               (a) The Board of Directors of the Company may at any time and for
any reason terminate or amend the Plan. Except as provided in Section 19 hereof,
no such termination can affect options previously granted, provided that an
Offering Period may be terminated by the Board of Directors on any Exercise Date
if the Board determines that the termination of the Offering Period or the Plan
is in the best interests of the Company and its stockholders. Except as provided
in Section 19 and this Section 20 hereof, no amendment may make any change in
any option theretofore granted which adversely affects the rights of any
participant. To the extent necessary to comply with Section 423 of the Code (or
any successor rule or provision or any other applicable law, regulation or stock
exchange rule), the Company shall obtain stockholder approval in such a manner
and to such a degree as required.

               (b) Without stockholder consent and without regard to whether any
participant rights may be considered to have been "adversely affected," the
Board (or its committee) shall be entitled to change the Offering Periods, limit
the frequency and/or number of changes in the amount withheld during an Offering
Period, establish the exchange ratio applicable to amounts withheld in a
currency other than U.S. dollars, permit payroll withholding in excess of the
amount designated by a participant in order to adjust for delays or mistakes in
the Company's processing of properly completed withholding elections, establish
reasonable waiting and adjustment periods and/or accounting and crediting
procedures to ensure that amounts applied toward the purchase of Common Stock
for each participant properly correspond with amounts withheld from the
participant's Compensation, and establish such other limitations or procedures
as the Board (or its committee) determines in its sole discretion advisable
which are consistent with the Plan.

               (c) In the event the Board determines that the ongoing operation
of the Plan may result in unfavorable financial accounting consequences, the
Board may, in its discretion and, to the extent necessary or desirable, modify
or amend the Plan to reduce or eliminate such accounting consequence including,
but not limited to:

                          (i) altering the Purchase Price for any Offering
Period including an Offering Period underway at the time of the change in
Purchase Price;

                          (ii) shortening any Offering Period so that Offering
Period ends on a new Exercise Date, including an Offering Period underway at the
time of the Board action; and

                          (iii) allocating shares.

               Such modifications or amendments shall not require stockholder
approval or the consent of any Plan participants.

        21. Notices. All notices or other communications by a participant to the
Company under or in connection with the Plan shall be deemed to have been duly
given when received in the form specified by the Company at the location, or by
the person, designated by the Company for the receipt thereof.

        22. Conditions Upon Issuance of Shares. Shares shall not be issued with
respect to an option unless the exercise of such option and the issuance and
delivery of such shares pursuant

                                      -9-
<PAGE>   10

thereto shall comply with all applicable provisions of law, domestic or foreign,
including, without limitation, the Securities Act of 1933, as amended, the
Securities Exchange Act of 1934, as amended, the rules and regulations
promulgated thereunder, and the requirements of any stock exchange upon which
the shares may then be listed, and shall be further subject to the approval of
counsel for the Company with respect to such compliance.

               As a condition to the exercise of an option, the Company may
require the person exercising such option to represent and warrant at the time
of any such exercise that the shares are being purchased only for investment and
without any present intention to sell or distribute such shares if, in the
opinion of counsel for the Company, such a representation is required by any of
the aforementioned applicable provisions of law.

        23. Term of Plan. The Plan shall become effective upon the earlier to
occur of its adoption by the Board of Directors or its approval by the
stockholders of the Company. It shall continue in effect for a term of ten (10)
years unless sooner terminated under Section 20 hereof.

        24. Automatic Transfer to Low Price Offering Period. To the extent
permitted by any applicable laws, regulations, or stock exchange rules if the
Fair Market Value of the Common Stock on any Exercise Date in an Offering Period
is lower than the Fair Market Value of the Common Stock on the Enrollment Date
of such Offering Period, then all participants in such Offering Period shall be
automatically withdrawn from such Offering Period immediately after the exercise
of their option on such Exercise Date and automatically re-enrolled in the
immediately following Offering Period.

                                      -10-
<PAGE>   11


                                    EXHIBIT A



                             PAIN THERAPEUTICS, INC.
                        2000 EMPLOYEE STOCK PURCHASE PLAN

                             SUBSCRIPTION AGREEMENT



______ Original Application                            Enrollment Date: ______

______ Change in Payroll Deduction Rate

______ Change of Beneficiary(ies)


1.      ____________________ hereby elects to participate in the Pain
        Therapeutics, Inc. 2000 Employee Stock Purchase Plan (the "Employee
        Stock Purchase Plan") and subscribes to purchase shares of the Company's
        Common Stock in accordance with this Subscription Agreement and the
        Employee Stock Purchase Plan.

2.      I hereby authorize payroll deductions from each paycheck in the amount
        of ____% of my Compensation on each payday (from 0 to 15%) during the
        Offering Period in accordance with the Employee Stock Purchase Plan.
        (Please note that no fractional percentages are permitted.)

3.      I understand that said payroll deductions shall be accumulated for the
        purchase of shares of Common Stock at the applicable Purchase Price
        determined in accordance with the Employee Stock Purchase Plan. I
        understand that if I do not withdraw from an Offering Period, any
        accumulated payroll deductions will be used to automatically exercise my
        option.

4.      I have received a copy of the complete Employee Stock Purchase Plan. I
        understand that my participation in the Employee Stock Purchase Plan is
        in all respects subject to the terms of the Plan. I understand that my
        ability to exercise the option under this Subscription Agreement is
        subject to stockholder approval of the Employee Stock Purchase Plan.

5.      Shares purchased for me under the Employee Stock Purchase Plan should be
        issued in the name(s) of (Employee or Employee and Spouse only).

6.      I understand that if I dispose of any shares received by me pursuant to
        the Plan within 2 years after the Enrollment Date (the first day of the
        Offering Period during which I purchased such shares) or one year after
        the Exercise Date, I will be treated for federal income tax purposes as
        having received ordinary income at the time of such disposition in an
        amount equal to the excess of the fair market value of the shares at the
        time such shares were purchased by me over the price which I paid for
        the shares. I hereby agree to notify the Company in writing within 30
        days after the date of any disposition of my shares and I will make
        adequate provision for Federal, state or other tax withholding
        obligations, if any, which arise upon the disposition of the Common
        Stock. The Company may, but will not be obligated to, withhold

<PAGE>   12
        from my compensation the amount necessary to meet any applicable
        withholding obligation including any withholding necessary to make
        available to the Company any tax deductions or benefits attributable to
        sale or early disposition of Common Stock by me. If I dispose of such
        shares at any time after the expiration of the 2-year and 1-year holding
        periods, I understand that I will be treated for federal income tax
        purposes as having received income only at the time of such disposition,
        and that such income will be taxed as ordinary income only to the extent
        of an amount equal to the lesser of (1) the excess of the fair market
        value of the shares at the time of such disposition over the purchase
        price which I paid for the shares, or (2) 15% of the fair market value
        of the shares on the first day of the Offering Period. The remainder of
        the gain, if any, recognized on such disposition will be taxed as
        capital gain.

7.      I hereby agree to be bound by the terms of the Employee Stock Purchase
        Plan. The effectiveness of this Subscription Agreement is dependent upon
        my eligibility to participate in the Employee Stock Purchase Plan.

8.      In the event of my death, I hereby designate the following as my
        beneficiary(ies) to receive all payments and shares due me under the
        Employee Stock Purchase Plan:


        NAME:  (Please print)
                             ---------------------------------------------------
                               (First)             (Middle)              (Last)



        -------------------------   --------------------------------------------
        Relationship

                                    --------------------------------------------
                                    (Address)
        Employee's Social
        Security Number:
                                            ------------------------------------
        Employee's Address:
                                            ------------------------------------

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

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


I UNDERSTAND THAT THIS SUBSCRIPTION AGREEMENT SHALL REMAIN IN EFFECT THROUGHOUT
SUCCESSIVE OFFERING PERIODS UNLESS TERMINATED BY ME.



Dated:
      ---------------------------    -------------------------------------------
                                     Signature of Employee


                                     -------------------------------------------
                                     Spouse's Signature (If beneficiary other
                                     than spouse)

                                      -2-

<PAGE>   13

                                    EXHIBIT B



                             PAIN THERAPEUTICS, INC.
                        2000 EMPLOYEE STOCK PURCHASE PLAN

                              NOTICE OF WITHDRAWAL



        The undersigned participant in the Offering Period of the Pain
Therapeutics, Inc. 2000 Employee Stock Purchase Plan which began on
____________, ______ (the "Enrollment Date") hereby notifies the Company that he
or she hereby withdraws from the Offering Period. He or she hereby directs the
Company to pay to the undersigned as promptly as practicable all the payroll
deductions credited to his or her account with respect to such Offering Period.
The undersigned understands and agrees that his or her option for such Offering
Period will be automatically terminated. The undersigned understands further
that no further payroll deductions will be made for the purchase of shares in
the current Offering Period and the undersigned shall be eligible to participate
in succeeding Offering Periods only by delivering to the Company a new
Subscription Agreement.

                                             Name and Address of Participant:

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

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

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


                                             Signature:

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

                                             Date:
                                                  ---------------------------