Document:

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                                                                     Exhibit 4.5

                                     WARRANT

                                (PHARMCHEM, INC.)

THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 NOR
REGISTERED OR QUALIFIED UNDER THE SECURITIES LAW OF ANY STATE; THIS WARRANT MAY
NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED IN CONTRAVENTION OF THE SECURITIES
ACT OR APPLICABLE STATE LAWS.

________SHARES COMMON STOCK                                SEPTEMBER ___  , 2001

THIS CERTIFIES THAT, for value received, ________________ ("Warrant Holder"), or
registered assigns, has the right to purchase from PHARMCHEM, INC. (the
"Company"), prior to September , 2006 (the "Expiration Date"), up to the number
of shares of the Common Stock of the Company set forth above ("Shares") at US$
3.00 per share ("Warrant Price").

            1. Registration of Warrant. The Company shall register this Warrant,
upon records to be maintained by the Company for that purpose (the "Warrant
Register"), in the name of the record Warrant Holder hereof from time to time.
The Company may deem and treat the registered Warrant Holder of this Warrant as
the absolute owner hereof for the purpose of any exercise hereof or any
distribution to the Warrant Holder, and for all other purposes, and the Company
shall not be affected by notice to the contrary.

            2. Restrictions on and Registration of Transfers and Exchanges.

                (a) The Warrant shall be exercisable and transferable only under
circumstances such that the exercise and/or transfer is exempt from the
requirements of registration under the Securities Act of 1933, as amended (the
"1933 Act") and any applicable state securities law. By acceptance hereof, the
Warrant Holder agrees to comply with the 1933 Act and such state securities law.
The Warrant and the rights granted to the holder are transferable, in whole or
in part, upon surrender of the Warrant as provided in Section 2(b) below.

                (b) The Company shall register the transfer of any portion of
this Warrant in the Warrant Register, upon surrender of this Warrant, with the
Form of Assignment attached hereto duly completed and signed, to the Company at
the office specified in or pursuant to Section 3(b). Upon any such registration
or transfer, a new warrant to purchase Common Stock, in substantially the form
of this Warrant (any such new warrant, a "New Warrant"), evidencing the portion
of this Warrant so transferred shall be issued to the transferee and a New
Warrant evidencing the remaining portion of this Warrant not so transferred, if
any, shall be issued to the transferring Warrant Holder. The acceptance of the
New Warrant by the transferee thereof shall be deemed the acceptance by such
transferee of all of the rights and obligations of a holder of a Warrant.

                (c) This Warrant is exchangeable upon the surrender hereof by
the Warrant Holder to the office of the Company specified in or pursuant to
Section 3(b) for one or

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more New Warrants, evidencing in the aggregate the right to purchase the number
of Warrant Shares which may then be purchased hereunder. Any such New Warrant
will be dated the date of such exchange, but reference shall be made to the
original date of the issuance of the Warrant.

            3. Duration and Exercise of Warrants.

                (a) This Warrant shall be exercisable by the registered Warrant
Holder on any business day before 5:00 P.M., Central time, at any time and from
time to time on or after the date hereof to and including the Expiration Date.
At 5:00 P.M., Central time on the Expiration Date, the portion of this Warrant
not exercised prior thereto shall be and become void and of no value.

                (b) Subject to Sections 2(b), 4 and 11, upon surrender of this
Warrant, with the Form of Election to Purchase attached hereto duly completed
and signed, to the Company at its office at 4600 Beach Street, Haltom City,
Texas 76137, Attn: Chief Financial Officer, or at such other address as the
Company may specify in writing to the then registered Warrant Holder, and upon
payment of the Warrant Price multiplied by the number of Warrant Shares that the
Warrant Holder intends to purchase hereunder, in lawful money of the United
States of America, in cash or by certified or official bank check or checks in
New York Clearing House Funds, all as specified by the Warrant Holder in the
Form of Election to Purchase, the Company shall promptly (but in no event later
than three (3) business days after the date of exercise) issue or cause to be
issued and cause to be delivered to or upon the written order of the Warrant
Holder and in such name or names as the Warrant Holder may designate, a
certificate for the Warrant Shares issuable upon such exercise. Any person so
designated by the Warrant Holder to receive Warrant Shares shall be deemed to
have become holder of record of such Warrant Shares as of the Date of Exercise
of this Warrant.

                A "Date of Exercise" means the date on which the Company shall
have received (i) this Warrant (or any New Warrant, as applicable), with the
Form of Election to Purchase attached hereto (or attached to such New Warrant)
appropriately completed and duly signed, and (ii) payment (in the manner set
forth above) of the Exercise Price for the number of Warrant Shares so indicated
by the holder hereof to be purchased unless the exercise of such Warrant is made
pursuant to the cashless exercise provision of Section 3(d) hereof.
Notwithstanding the foregoing, the Company shall not be required to issue any
Shares unless the Company has determined that the issuance of Shares does not
violate the 1933 Act or any applicable state securities law.

                (c) This Warrant shall be exercisable, either in its entirety
or, from time to time, for all or a portion of the number of Warrant Shares
available under the Warrant. If this Warrant is exercised at any time for less
than all of the Warrant Shares which may be purchased under this Warrant, the
Company shall issue or cause to be issued, at its expense, a New Warrant
evidencing the right to purchase the remaining number of Warrant Shares for
which no exercise has been evidenced by this Warrant.

                (d) In lieu of exercising this Warrant pursuant to subsections
3(a)-(c) above, the Warrant Holder may elect to receive shares equal to the
value of this Warrant (or the portion thereof being canceled) by surrender of
this Warrant at the principal office of the Company together with notice of such
election, in which event the Company shall issue to the

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Warrant Holder a number of shares of the Company's Warrant Stock (rounded down
to the nearest whole number) computed using the following formula:

                                                   X = Y (A-B)
                                                       -------
                                                          A

                      Where

                      X =    the number of shares of Common Stock to be issued
                             to the Holder;

                      Y =    the number of shares of Common Stock purchasable
                             under this Warrant or the portion thereof being
                             cancelled (at the date of such calculation);

                      A =    the Fair Market Value (defined below) of one
                             share of the Company's Common Stock; and

                      B =    Warrant Price (as adjusted to the date of such
                             calculation).

                (e) Fair Market Value" means, as of any date, the value of a
share of the Company's Common Stock determined as follows:

                    (i) if such stock is then quoted on the Nasdaq National
Market, its closing price on the Nasdaq National Market on the date of
determination as reported in The Wall Street Journal;

                    (ii) if such stock is publicly traded and is then listed on
a national securities market or exchange, its closing price on the date of
determination on the principal national securities exchange on which the stock
is listed or admitted to trading as reported in The Wall Street Journal;

                    (iii) if such stock is publicly traded but is not quoted on
the Nasdaq National Market nor listed or admitted to trading on a national
securities exchange, the average of the closing bid and asked prices on the date
of determination as reported by The Wall Street Journal (or, if not so reported,
as otherwise reported by any newspaper or other source as the Board of Directors
of the Company may determine in good faith); or

                    (iv) if none of the foregoing is applicable, Fair Market
Value shall initially be determined by the directors of the Company. If the
Warrant Holder (the "Contesting Holder") notifies the Company within five (5)
days after receiving notification of the directors' determination of the fair
market value of such stock that it objects to their determination of such fair
market value, the Company and the Contesting Holder shall attempt to agree on
the fair market value of such stock. In the event that the Company and the
Contesting Holder fail to agree on the fair market value of such stock within
fifteen (15) days after receipt by the Company of the objection notice referred
to above, the Company and the Contesting Holder shall select an independent
appraiser, who shall be a nationally recognized investment banking firm, to
conduct an appraisal of such stock, which appraisal shall determine the fair
market value (without making any discount for lack of transferability or
minority interests) of

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such stock. If the Company and the Contesting Holder are unable to agree on the
selection of an independent appraiser within fifteen (15) days after the
commencement of such selection process, then an independent appraiser meeting
the specifications described above shall be selected by the President of the
American Arbitration Association in the San Francisco, California metropolitan
area. The independent appraiser shall then promptly conduct an appraisal to
determine the fair market value of the such stock. In such case, the fair market
shall be that as is determined by the appraiser. Such appraisal shall be paid
for by the Company.

            4. Payment of Taxes. The Company will pay all documentary stamp
taxes attributable to the issuance of Warrant Shares upon the exercise of this
Warrant; provided, however, that the Company shall not be required to pay any
tax which may be payable in respect of any transfer involved in the registration
of any certificates for Warrant Shares or Warrants in a name other than that of
the Warrant Holder, and the Company shall not be required to issue or cause to
be issued or deliver or cause to be delivered the certificates for Warrant
Shares unless or until the person or persons requesting the issuance thereof
shall have paid to the Company the amount of such tax or shall have established
to the satisfaction of the Company that such tax has been paid. The Warrant
Holder shall be responsible for all other tax liability that may arise as a
result of holding or transferring this Warrant or receiving Warrant Shares upon
exercise hereof.

            5. Replacement of Warrant. If this Warrant is mutilated, lost,
stolen or destroyed, the Company shall issue or cause to be issued in exchange
and substitution for and upon cancellation hereof, or in lieu of and
substitution for this Warrant, a New Warrant, but only upon receipt of evidence
reasonably satisfactory to the Company of such loss, theft or destruction and
indemnity, if requested, reasonably satisfactory to it.

            6. Reservation of Warrant Shares. The Company covenants that it will
at all times reserve and keep available out of the aggregate of its authorized
but unissued Common Stock, solely for the purpose of enabling it to issue
Warrant Shares upon exercise of this Warrant as herein provided, the number of
Warrant Shares which are then issuable and deliverable upon the exercise of this
entire Warrant, free from preemptive rights or any other actual contingent
purchase rights of persons other than the Warrant Holder (taking into account
the adjustments provided in Section 7). All Warrant Shares that shall be so
issuable and deliverable shall, upon issuance and the payment of the applicable
Exercise Price in accordance with the terms hereof, be duly and validly
authorized, issued and fully paid and nonassessable, and free from all taxes,
liens, claims and encumbrances and will not be subject to preemptive rights or
other similar rights of stockholders of the Company, other than (a) restrictions
on transferability as may be applicable under federal and state securities laws;
or (b) those created by the Warrant Holder.

            7. Certain Adjustments. The Exercise Price and number of Warrant
Shares issuable upon exercise of this Warrant are subject to adjustment from
time to time as set forth in this Section 7.

            (a) If the Company, at any time while this Warrant is outstanding,
(i) shall pay a stock dividend or otherwise make a distribution or distributions
on shares of its Common Stock or any class or series of Preferred Stock payable
in shares of Common Stock, (ii) subdivide outstanding shares of Common Stock
into a larger number of shares, or (iii) combine outstanding shares of Common
Stock into a smaller number of shares, [x] the Warrant Price shall be multiplied
by a fraction of which the numerator shall be the number of

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shares of Common Stock (excluding treasury shares, if any, but including
warrants or options that would be included for purposes of determining earnings
per share in accordance with generally accepted accounting principals)
outstanding before such event and of which the denominator shall be the number
of shares of Common Stock (excluding treasury shares, if any, but including
warrants or options that would be included for purposes of determining earnings
per share in accordance with generally accepted accounting principals)
outstanding after such event and, and [y] the number of Warrant Shares issuable
upon exercise of this Warrant shall be multiplied by a fraction of which the
numerator shall be the number of shares of Common Stock (excluding treasury
shares, if any, but including warrants or options that would be included for
purposes of determining earnings per share in accordance with generally accepted
accounting principles) outstanding after such event and of which the denominator
shall be the number of shares of Common Stock (excluding treasury shares, if
any, but including warrants or options that would be included for purposes of
determining earnings per share in accordance with generally accepted accounting
principles) outstanding before such event. Any adjustment made pursuant to this
Section shall become effective immediately after the record date for the
determination of stockholders entitled to receive such dividend or distribution
and shall become effective immediately after the effective date in the case of a
subdivision or combination, and shall apply to successive subdivisions and
combinations.

            (b) For the purposes of this Section 7, the following clauses shall
also be applicable:

                    (i) All calculations under this Section 7 shall be made to
the nearest cent or the nearest 1/100th of a share, as the case may be.

                    (ii) No adjustment in the Warrant Price shall be made if
such adjustment would result in a change in the Warrant Price of less than $.01,
provided that any such adjustments not made shall be carried forward and taken
into account at the time of any subsequent adjustment in the Warrant Price.

                    (iii) Whenever the Warrant Price is adjusted pursuant to
this Section 7, the Company shall promptly mail or cause to be mailed to each
Warrant Holder a notice setting forth the Warrant Price after such adjustment
and setting forth a brief statement of the facts requiring such adjustment.

                    (iv) All determinations with respect to adjustments by the
Company hereunder shall be made by the directors of the Company. If a Warrant
Holder (a "Contesting Holder") notifies the Company within five (5) days after
receiving notification of the directors' determination of such adjustment that
it objects to their determination of such adjustment, the Company and the
Contesting Holder shall attempt to agree on such adjustment. In the event that
the Company and the Contesting Holder fail to agree on such adjustment within
fifteen (15) days after receipt by the Company of the objection notice referred
to above, the Company and the Contesting Holder shall select a nationally
recognized investment banking firm to determine such adjustment. If the Company
and the Contesting Holder are unable to agree on the selection of an investment
banking firm within fifteen (15) days after the commencement of such selection
process, then an investment banking firm meeting the specifications described
above shall be selected by the President of the American Arbitration Association
in the San Francisco, California metropolitan area. Such firm shall then
promptly determine such

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adjustment and the adjustment shall be that so determined by the investment
banking firm. The fees of such firm shall be paid for by the Company.

            8. Notice of Major Transactions. If, at any time while this Warrant
is outstanding:

                (a) the Company shall consolidate with or merge into any
corporation; or

                (b) the Company shall reclassify its outstanding shares of
Common Stock (other than in a manner referred to in Section 7(a)); or

                (c) there shall occur any share exchange pursuant to which all
of the outstanding shares of Common Stock are converted into other securities or
property; or

                (d) the Company shall sell substantially all of its assets in
such a way that holders of Common Stock shall be entitled to receive other
securities or property; or

                (e) the Company shall distribute to all holders of Common Stock
evidences of its indebtedness or assets (other than cash dividends) or rights or
warrants to subscribe for or purchase any security; or

                (f) the Company shall declare a dividend (or any other
distribution) on its Common Stock in Common Stock; or

                (g) the Company shall declare a special nonrecurring cash
dividend on or a redemption of its Common Stock; or

                (h) the Company shall issue or cause to be issued to all holders
of its Common Stock rights or warrants to subscribe for or purchase any shares
of capital stock; or

                (i) the approval of any stockholders of the Company shall be
required in connection with any reclassification of the Common Stock of the
Company, any consolidation or merger to which the Company is a party, any sale
or transfer of all or substantially all of the assets of the Company, or any
compulsory share exchange whereby the Common Stock is converted into other
securities, cash or property; or

                (j) the Company shall authorize the voluntary dissolution,
liquidation or winding up of the affairs of the Company,

then the Company shall cause to be mailed to each Warrant Holder at its last
address as it shall appear in the Warrant Register, at least five (5) calendar
days prior to the applicable record or effective date for such action or
transaction, a notice stating (i) the date on which a record is to be taken for
the purpose of such action, or if a record is not to be taken, the date as of
which the holders of Common Stock of record to be entitled to the benefit of any
such action is to be determined, or (ii) the date on which such transaction is
expected to become effective or close, and, if applicable, the date as of which
it is expected that holders of Common Stock of record shall be entitled to
exchange their shares of Common Stock for securities, cash or other property
deliverable upon such transaction; provided that the failure to mail such notice
or any defect

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therein or in the mailing thereof shall not affect the validity of the corporate
action required to be specified in such notice.

        For the purposes of clauses (e), (f), (g) and (h) of this subsection,
the Warrant Holder shall be entitled, upon exercise of the Warrant for the
purchase of any or all of the Warrant Shares, to receive the amount of such
assets (or rights) which would have been payable to the Warrant Holder or to
participate in such transaction had such Warrant Holder been the holder of such
shares of Common Stock on the record date for determination of stockholders
entitled to such distribution or to participate in such transaction .

            9. Fractional Shares. The Company shall not be required to issue or
cause to be issued fractional Warrant Shares on the exercise of this Warrant.
The number of full Warrant Shares which shall be issuable upon the exercise of
this Warrant shall be computed on the basis of the aggregate number of Warrant
Shares purchasable on exercise of this Warrant so presented. If any fraction of
a Warrant Share would, except for the provisions of this Section 9, be issuable
on the exercise of this Warrant, the Company shall, at its option, (a) pay an
amount in cash equal to the Warrant Price multiplied by such fraction or (b)
round the number of Warrant Shares issuable, up to the next whole number of such
shares.

            10. Notices. Any and all notices or other communications or
deliveries hereunder shall be in writing and shall be deemed given and effective
on the earliest of (i) the date of transmission, if such notice or communication
is delivered via facsimile at the facsimile telephone number specified in this
Section prior to 4:30 p.m. (Eastern time) in the case of notices to the Warrant
Holder or 4:30 p.m. (Central time) in the case of notices to the Company, in
each case on a business day, (ii) the business day after the date of
transmission, if such notice or communication is delivered via facsimile at the
facsimile telephone number specified in this Section later than 4:30 p.m.
(Eastern time) in the case of notices to the Warrant Holder or 4:30 p.m.
(Central time) in the case of notices to the Company, in each case on any date
and earlier than 11:59 p.m. (Eastern time) in the case of notices to the Warrant
Holder or 11:59 p.m. (Central time) in the case of notices to the Company on
such date, (iii) the business day following the date of mailing, if sent by
nationally recognized overnight courier service, or (iv) upon actual receipt by
the party to whom such notice is required to be given. The addresses for such
communications shall be: (i) if to the Company, to 4600 Beach Street, Haltom
City, Texas 76137, Attn: Chief Financial Officer, or (ii) if to the Warrant
Holder, to the Warrant Holder at the address or facsimile number appearing on
the Warrant Register or such other address or facsimile number as the Warrant
Holder may provide to the Company in accordance with this Section 10.

            11. Warrant Agent.

                (a) The Company shall serve as warrant agent under this Warrant.
Upon thirty (30) days' notice to the Warrant Holder, the Company may appoint a
new warrant agent.

                (b) Any corporation into which the Company or any new warrant
agent may be merged or any corporation resulting from any consolidation to which
the Company or any new warrant agent shall be a party or any corporation to
which the Company or any new warrant agent transfers substantially all of its
corporate trust or shareholders services business

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shall be a successor warrant agent under this Warrant without any further act.
Any such successor warrant agent shall promptly cause notice of its succession
as warrant agent to be mailed (by first class mail, postage prepaid) to the
Warrant Holder at the Warrant Holder's last address as shown on the Warrant
Register.

            12. Miscellaneous.

                (a) This Warrant shall be binding on and inure to the benefit of
the parties hereto and their respective successors and permitted assigns. This
Warrant may be amended only in writing signed by the Company and the Warrant
Holder.

                (b) Subject to Section 12(a), above, nothing in this Warrant
shall be construed to give to any person or corporation other than the Company
and the Warrant Holder any legal or equitable right, remedy or cause under this
Warrant; this Warrant shall be for the sole and exclusive benefit of the Company
and the Warrant Holder.

                (c) This Warrant shall be governed by and construed and enforced
in accordance with the internal laws of the State of Delaware without regard to
the principles of conflicts of law thereof.

                (d) The headings herein are for convenience only, do not
constitute a part of this Warrant and shall not be deemed to limit or affect any
of the provisions hereof.

                (e) In case any one or more of the provisions of this Warrant
shall be invalid or unenforceable in any respect, the validity and
enforceability of the remaining terms and provisions of this Warrant shall not
in any way be affected or impaired thereby and the parties will attempt in good
faith to agree upon a valid and enforceable provision which shall be a
commercially reasonable substitute therefor, and upon so agreeing, shall
incorporate such substitute provision in this Warrant.

                (f) This Warrant shall not entitle the Warrant Holder to any
voting rights, pre-emptive rights or rights as a stockholder of the Company.

                (g) Any amendment to this Warrant shall be in writing executed
by the Company and the Warrant Holder.

                (h) This Warrant is being issued pursuant to a Note and Warrant
Purchase Agreement executed by the Company and the Warrant Holder and the holder
of this Warrant is entitled to all rights set forth therein.

IN WITNESS WHEREOF, PharmChem, Inc. has caused this Warrant to be signed by its
duly authorized officer as of the date above.

                                            PHARMCHEM, INC.

                                            By:
                                                --------------------------------
                                            Its:
                                                --------------------------------

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                             EXHIBIT "1" to WARRANT

                          FORM OF ELECTION TO PURCHASE

(To be executed by the Warrant Holder to exercise the right to purchase shares
of Common Stock under the foregoing Warrant)

To PharmChem, Inc.:

        In accordance with the Warrant enclosed with this Form of Election to
Purchase, the undersigned ("Warrant Holder") hereby irrevocably elects to
acquire _____________ shares of Common Stock (the "Shares"), $.001 par value per
share, of PharmChem, Inc. and (check the applicable provision):

        ____ encloses herewith $________ in cash or certified or official bank
check or checks in New York Clearing House funds, which sum represents the
aggregate Warrant Price (as defined in the Warrant) for the number of shares of
Common Stock to which this Form of Election to Purchase relates, together with
any applicable taxes payable by the undersigned pursuant to the Warrant;

                                       or

        ____ elects to acquire such shares of Common Stock pursuant to the
cashless exercise provision (Section 3(d)) of the Warrant.

                                                PLEASE INSERT SOCIAL SECURITY OR
                                                       TAX IDENTIFICATION NUMBER

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

--------------------------------------------------------------------------------
                         (Please print name and address)

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

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

        If the number of shares of Common Stock issuable upon this exercise
shall not be all of the shares of Common Stock which the undersigned is entitled
to purchase in accordance with the enclosed Warrant, the undersigned requests
that a New Warrant (as defined in the Warrant) evidencing the right to purchase
the shares of Common Stock not issuable pursuant to the exercise evidenced
hereby be issued in the name of and delivered to:

--------------------------------------------------------------------------------
                         (Please print name and address)

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

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

Dated: ______________ , 200_    Name of Warrant Holder:

                                (Print) ________________________________________

                                (By:) __________________________________________
                                (Name:) ________________________________________
                                (Title:) _______________________________________

                                (Signature must conform in all respects to name
                                of Warrant Holder as specified on the face of
                                the Warrant)

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                               FORM OF ASSIGNMENT

           [To be completed and signed only upon transfer of Warrant]

        FOR VALUE RECEIVED, the undersigned hereby sells, assigns and transfers
unto ________________________________ the right represented by the within
Warrant to purchase ____________ shares of Common Stock of PharmChem, Inc.
Common Stock to which the within Warrant relates and appoints ________________
attorney to transfer said right on the books of PharmChem, Inc. with full power
of substitution in the premises.

Dated:

_______________, 200_

                                ------------------------------------------------
                                (Signature must conform in all respects to name
                                of Warrant Holder as specified on the face of
                                the Warrant)

                                ------------------------------------------------
                                Address of Transferee

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

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

                                ------------------------------------------------
                                Social Security or Tax Identification Number

                                      -10-<PAGE>   1
                                                                     Exhibit 4.6

           AMENDMENT TO LOAN AND SECURITY AGREEMENT AND LIMITED WAIVER

     This Amendment to Loan and Security Agreement and Limited Waiver (this
"Agreement") is entered into as of September 12, 2001, by and between COMERICA
BANK-CALIFORNIA ("Bank") and PHARMCHEM, INC. (the "Borrower"), with reference to
the following facts:

     A.   Borrower has borrowed funds from Bank pursuant to that certain Amended
and Restated Loan and Security Agreement by and between Bank and Borrower dated
as of May 15, 2000, as amended (the "Loan Agreement").

     B.   As of the date hereof, there is owing under the Loan Agreement a
principal amount of $6,591,148.31, together with accrued but unpaid interest and
costs of enforcement. Such amounts, plus accruing interest and costs and accrued
and accruing attorneys' fees and costs are hereinafter sometimes referred to
herein as the "Existing Debt."

     C.   One or more Events of Default have occurred under the Loan Agreement
by virtue of Borrower's failure to comply with Sections 6.8, 6.9, 6.10, 6.11 and
6.12 of the Loan Agreement as of certain dates through the date hereof. Such
Events of Default entitle Bank immediately to enforce all the remedies set forth
in the Loan Agreement. Borrower has asked Bank to waive such Events of Default,
and to amend certain provisions of the Loan Agreement, and Bank has agreed,
provided Borrower enters into this Agreement.

     NOW, THEREFORE, for good and valuable consideration, the parties agree as
follows:

     1.   Defined Terms. Capitalized terms not otherwise defined herein shall
have the same meanings as set forth in the Loan Agreement.

     2.   Acknowledgement of Liability. As of the date of this Agreement,
Borrower owes Bank an amount equal to the Existing Debt. Borrower reaffirms all
of its obligations under the Loan Agreement and hereby forever waives and
relinquishes any and all claims, offsets or defenses that Borrower may now have
with respect to the payment of sums due to Bank and the performance of other
obligations under the Loan Agreement. The security interests granted to Bank in
the Loan Agreement in the Collateral remain perfected, first priority liens.

     3.   Limited Waiver. Subject to the conditions contained herein and
performance by Borrower of all of the terms of this Agreement and the Loan
Documents after the date hereof, and in reliance on the representations and
warranties of the Borrower set forth herein, Bank hereby waives Borrower's
obligation to comply with Sections 6.8, 6.9, 6.10, 6.11 and 6.12 through the
date hereof. The waiver set forth herein shall be limited precisely as written
and relates solely to the waiver of compliance by the Borrower with Sections
6.8, 6.9, 6.10, 6.11 and 6.12 of the Loan Agreement through the date hereof in
the manner and to the extent described above, and nothing in this Agreement
shall be deemed to (i) constitute a waiver of compliance by Borrower with those
Sections in any other instance, or (ii) constitute a waiver of any other Event
of Default or other failure by Borrower to perform in accordance with the Loan
Agreement or the Loan Documents, or (iii) prejudice any right or remedy that
Bank may now have or may have in the future under or in connection with the Loan
Agreement or the Loan Documents.

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     4.   Repayment. Borrower shall continue to make all payments as they become
due under the Loan Agreement.

     5.   Amendments to Loan Agreement. The Loan Agreement is hereby amended as
follows:

          (a)  The following defined terms in Section 1.1 are amended to read as
follows:

               "Committed Revolving Line" means a credit extension of up to Five
     Million Seven Hundred Fifty Thousand Dollars ($5,750,000).

               "Current Assets" means, as of any applicable date, all amounts
     that should, in accordance with GAAP, be included as current assets on the
     unconsolidated balance sheet of Borrower as at such date.

               "Current Liabilities" means, as of any applicable date, the sum,
     determined on an unconsolidated basis, of all liabilities of Borrower which
     may properly be classified as current liabilities in accordance with GAAP.

               "Effective Tangible Net Worth" means at any date as of which the
     amount thereof shall be determined, the financial statement net worth of
     Borrower, plus, without duplication, (a) Subordinated Debt, and (b) any
     imputed dividend received from any Subsidiary, minus, without duplication,
     (i) intangible assets such as goodwill, and (ii) Investments in
     Subsidiaries, all as determined in accordance with GAAP.

               "Total Liabilities" means at any date as of which the amount
     thereof shall be determined, all obligations that should, in accordance
     with GAAP be classified as liabilities on the unconsolidated balance sheet
     of Borrower, including in any event all Indebtedness.

          (b)  Section 6.3(b) is amended by deleting the phrase "ninety (90)
days" where it appears and replacing it with "one hundred twenty (120) days."

          (c)  Section 6.3 is further amended by adding the following paragraph
at the end thereof:

               Borrower shall deliver to Bank as soon as available, but in any
     event within thirty (30) days after the end of each month, a company
     prepared balance sheet, income statement and cash flow statement covering
     Borrower's consolidated domestic operations during such period, in a form
     and certified by an Officer of Borrower reasonably acceptable to Bank.

          (d)  Section 6.8 is amended to read as follows:

               6.8 Current Ratio. Borrower shall maintain, as of the last day of
     each fiscal quarter, a ratio of Current Assets to Current Liabilities of at
     least 0.70 to 1.0.

          (e)  Section 6.9 is amended to read as follows:

               6.9 Quarterly Cash Flow Coverage. Borrower shall maintain, as of
     the last day of each fiscal quarter commencing with the fiscal quarter
     ended March 30, 2002, a Quarterly Cash Flow Ratio of not less than 1.25 to
     1.0. "Quarterly Cash Flow Ratio" is defined as the Net Profit after tax of
     the Borrower for any fiscal quarter of determination, plus depreciation and

                                       2
<PAGE>   3

     amortization for such quarter, all of the foregoing multiplied by four,
     divided by the current portion of all term debt, including the current
     portion of capital lease obligations.

          (f)  Section 6.10 is amended to read as follows:

               6.10 Total Liabilities-Effective Tangible Net Worth. Borrower
     shall maintain, as of the last day of each fiscal quarter, a ratio of Total
     Liabilities to Effective Tangible Net Worth of not more than 2.75 to 1.0.

          (g)  The first sentence of Section 6.11 is amended to read as follows:

               The aggregate amount of all Capital Expenditures of Borrower
     shall not exceed (i) Four Million Five Hundred Thousand Dollars
     ($4,500,000) during the Borrower's 2001 fiscal year, or (ii) Two Million
     Six Hundred Thousand Dollars ($2,600,000) in any fiscal year of Borrower
     thereafter.

          (h)  Section 6.12 is amended to read as follows:

               6.12 Effective Tangible Net Worth. Borrower shall maintain, as of
     the last day of each fiscal quarter, an Effective Tangible Net Worth of not
     less than (i) Six Million Four Hundred Thousand Dollars ($6,400,000) as of
     September 30, 2001, and (ii) Six Million Dollars ($6,000,000) as of the
     last day of each fiscal quarter of Borrower thereafter, commencing with the
     quarter ending December 31, 2001.

          (i)  A new Section 6.14 is added to the Loan Agreement, which shall
read as follows:

               6.14 Receipt of Subordinated Debt. On or before September 30,
     2001, Borrower shall have received cash proceeds of at least Seven Hundred
     Fifty Thousand Dollars ($750,000) from the issuance of Subordinated Debt.
     On or before October 31, 2001, Borrower shall have used its best commercial
     efforts to obtain an additional Seven Hundred Fifty Thousand Dollars
     ($750,000) from the issuance of Subordinated Debt. Bank hereby approves
     Borrower's incurrence of, and the making of payments by Borrower under, up
     to Two Million Five Hundred Thousand Dollars ($2,500,000) of such
     Subordinated Debt, subject to the provisions of Section 7.9 of this
     Agreement and provided that each lender under such Subordinated Debt
     executes a subordination agreement in form and substance acceptable to
     Bank. Bank further acknowledges that such lender(s) under such Subordinated
     Debt may be Affiliates of Borrower.

          (j)  A new Section 6.15 is added to the Loan Agreement, which shall
read as follows:

               6.15 Receipt of Dividend. On or before October 31, 2001, Borrower
     shall have received cash proceeds of at least One Million Four Hundred
     Thousand Dollars ($1,400,000) in imputed dividend payments from Borrower's
     wholly-owned Subsidiary.

          (k)  A new Section 6.16 is added to the Loan Agreement, which shal
read as follows:

                                       3
<PAGE>   4

               6.16 Sale and Leaseback. Bank hereby approves of the sale and
     leaseback of leasehold improvements and other specific items of equipment
     not financed by Bank in an amount of up to Two Million Two Hundred Thousand
     Dollars ($2,200,000).

          (l)  Section 7.4 is amended by adding the following sentence at the
end thereof:

               Bank hereby consents to the incurrence of Indebtedness by
     Borrower's wholly-owned Subsidiary of not more than $2,500,000, which
     Indebtedness shall constitute Permitted Indebtedness.

     6.   Ratification by Borrower of Bank's First Priority Security Interest in
Collateral. Borrower hereby confirms and ratifies Bank's first priority lien and
security interest in and to all Collateral. Borrower shall execute such security
agreements, financing statements and other documents as Bank may from time to
time reasonably request to carry out the terms of this Agreement and the Loan
Agreement. Such liens and security interests shall secure all of the obligations
of Borrower under this Agreement and the Loan Documents.

     7.   Representations and Warranties.

          (a)  Borrower hereby represents and warrants that no Event of Default
or failure of condition has occurred or exists, or would exist with notice or
lapse of time or both under any of the Loan Agreement, other than the Events of
Default described in Recital C.

          (b)  All representations and warranties of Borrower in this Agreement
and the other Loan Agreement are true and correct as of the date hereof, and
shall survive the execution of this Agreement.

     8.   Default. In addition to all other Events of Default under the Loan
Agreement, the following shall constitute an Event of Default:

          (a)  Borrower's failure to pay any amount when due under this
Agreement or to perform any covenant or other agreement contained in this
Agreement or any other document entered into pursuant hereto.

     9.   Conditions Precedent. The effectiveness of this Agreement is subject
to receipt by Bank of the following, in each case in form and substance
acceptable to Bank:

          (a)  This Agreement;

          (b)  Payment to Bank of a non-refundable amendment fee in the amount
               of $2,500;

          (c)  Payment of all Bank Expenses incurred in connection with this
Agreement; and

          (d)  Such other documents and completion of such other matters as Bank
may reasonably deem necessary or appropriate.

     10.  Events of Default. Borrower acknowledges that Events of Default have
occurred under the Loan Agreement that, but for this Agreement, would have
entitled Bank to exercise all the remedies available to Bank under the Loan
Agreement and applicable law.

                                       4
<PAGE>   5

     11.  Release.

          (a)  Borrower acknowledges that Bank would not enter into this
Agreement without Borrower's assurance that Borrower has no claims against Bank
or any of Bank's officers, directors, employees or agents. Except for the
obligations arising hereafter under this Agreement, Borrower releases Bank, any
person or entity that has obtained any interest from Bank under the Loan
Agreement and each of Bank's and entity's officers, directors and employees from
any known or unknown claims which Borrower now has against Bank of any nature,
including any claims that Borrower, its successors, counsel, and advisors may in
the future discover they would have now had if they had known facts not now
known to them, whether founded in contract, in tort or pursuant to any other
theory of liability, including but not limited to any claims arising out of or
related to the Loan Agreement or the transactions contemplated thereby. Borrower
waives the provisions of California Civil Code section 1542, which states:

          A general release does not extend to claims which the creditor does
          not know or suspect to exist in his favor at the time of executing the
          release, which if known by him must have materially affected his
          settlement with the debtor.

          (b)  The provisions, waivers and releases set forth in this section
are binding upon Borrower and Borrower's agents, employees, assigns and
successors in interest. The provisions, waivers and releases of this section
shall inure to the benefit of Bank and its agents, employees, officers,
directors, assigns and successors in interest.

          (c)  Borrower warrants and represents that Borrower is the sole and
lawful owner of all right, title and interest in and to all of the claims
released hereby and Borrower has not heretofore voluntarily, by operation of law
or otherwise, assigned or transferred or purported to assign or transfer to any
person any such claim or any portion thereof. Borrower shall indemnify and hold
harmless Bank from and against any claim, demand, damage, debt, liability
(including payment of attorneys' fees and costs actually incurred whether or not
litigation is commenced) based on or arising out of any assignment or transfer.

          (d)  The provisions of this Section shall survive payment in full of
the Obligations, full performance of all the terms of this Agreement and the
Loan Agreement, and/or Bank's actions to exercise any remedy available under the
Loan Agreement or otherwise.

     12.  Further Assurances. Borrower will take such other actions as Bank may
reasonably request from time to time to perfect or continue Bank's security
interests in Borrower's property, and to accomplish the objectives of this
Agreement.

     13.  Consultation of Counsel. Borrower acknowledges that Borrower has had
the opportunity to be represented by legal counsel of its own choice throughout
all of the negotiations that preceded the execution of this Agreement. Borrower
has executed this Agreement after reviewing and understanding each provision of
this Agreement and without reliance upon any promise or representation of any
person or persons acting for or on behalf of Bank. Borrower further acknowledges
that Borrower and its counsel have had adequate opportunity to make whatever
investigation or inquiry they may deem necessary or desirable in connection with
the subject matter of this Agreement prior to the execution hereof and the
delivery and acceptance of the consideration described herein.

                                       5
<PAGE>   6

     14.  Miscellaneous.

          (a)  Successors and Assigns. This Agreement shall be binding upon and
shall inure to the benefit of Borrower and Bank and their respective successors
and assigns; provided, however, that the foregoing shall not authorize any
assignment by Borrower of its rights or duties hereunder.

          (b)  Integration. This Agreement and any documents executed in
connection herewith or pursuant hereto contain the entire agreement between the
parties with respect to the subject matter hereof and supersede all prior
agreements, understandings, offers and negotiations, oral or written, with
respect thereto and no extrinsic evidence whatsoever may be introduced in any
judicial or arbitration proceeding, if any, involving this Agreement; except
that any financing statements or other agreements or instruments filed by Bank
with respect to Borrower shall remain in full force and effect.

          (c)  Entire Agreement. This Agreement and the Loan Documents contain
the entire agreement of the parties hereto and supersede any other oral or
written agreements or understandings with respect to the subject matter hereof
and thereof.

          (d)  Course of Dealing; Waivers. No course of dealing on the part of
Bank or its officers, nor any failure or delay in the exercise of any right by
Bank, shall operate as a waiver thereof, and any single or partial exercise of
any such right shall not preclude any later exercise of any such right. Bank's
failure at any time to require strict performance by Borrower of any provision
shall not affect any right of Bank thereafter to demand strict compliance and
performance. Any suspension or waiver of a right must be in writing signed by an
officer of Bank.

          (e)  Time is of the Essence. Time is of the essence as to each and
every term and provision of this Agreement and the Loan Documents.

          (f)  Counterparts. This Agreement may be signed in counterparts and
all of such counterparts when properly executed by the appropriate parties
thereto together shall serve as a fully executed document, binding upon the
parties.

          (g)  Legal Effect. The Loan Documents remain in full force and effect.
If any provision of this Agreement conflicts with applicable law, such provision
shall be deemed severed from this Agreement, and the balance of this Agreement
shall remain in full force and effect.

          (h)  WAIVER OF JURY. BANK AND BORROWER ACKNOWLEDGE AND AGREE THAT THE
TIME AND EXPENSE REQUIRED FOR TRIAL BY JURY EXCEED THE TIME AND EXPENSE REQUIRED
FOR A BENCH TRIAL AND HEREBY WAIVE, TO THE EXTENT PERMITTED BY LAW, TRIAL BY
JURY OF ANY CLAIM OR CAUSE OF ACTION BASED UPON, RELATED TO OR ARISING OUT OF
THE TRANSACTIONS CONTEMPLATED BY THE LOAN AGREEMENT, INCLUDING CONTRACT CLAIMS,
TORT CLAIMS, BREACH OF DUTY CLAIMS, AND ALL OTHER COMMON LAW OR STATUTORY
CLAIMS. EACH PARTY RECOGNIZES AND AGREES THAT THE FOREGOING WAIVER CONSTITUTES A
MATERIAL INDUCEMENT FOR IT TO ENTER INTO THIS AGREEMENT. EACH PARTY REPRESENTS
AND WARRANTS THAT IT HAS REVIEWED THIS WAIVER WITH ITS LEGAL COUNSEL AND THAT IT
KNOWINGLY AND VOLUNTARILY WAIVES ITS JURY TRIAL RIGHTS FOLLOWING CONSULTATION
WITH LEGAL COUNSEL.

          (i)  Assignment. Borrower consents to Bank's assignment of all or any
part of Bank's rights under this Agreement and the Loan Agreement.

                                       6
<PAGE>   7

          (j)  Power of Attorney. Borrower confirms that the irrevocable power
of attorney granted in the Loan Agreement remains in full force and effect

          (k)  Choice of Law and Venue. This Agreement shall be governed by, and
construed in accordance with, the internal laws of the State of California,
without regard to principles of conflicts of law. Each of Borrower and Bank
submits to the exclusive jurisdiction of the state and Federal courts located in
the County of Santa Clara, State of California.

     IN WITNESS WHEREOF the undersigned have executed this Agreement as of the
first date above written.

                                           PHARMCHEM, INC.

                                           By:  /s/ DAVID LATTANZIO
                                              -------------------------
                                           Title:  VICE PRESIDENT
                                                 ----------------------

                                           COMERICA BANK-CALIFORNIA

                                           By:  /s/ JAMES L. WEBER
                                              -------------------------
                                           Title:  VICE PRESIDENT
                                                 ----------------------

                                       7

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