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                                                                   EXHIBIT 10.42

                    INTELLECTUAL PROPERTY SECURITY AGREEMENT


        This Intellectual Property Security Agreement is entered into as of May
15, 2000 by and between COMERICA BANK-CALIFORNIA ("Bank") and PHARMCHEM
LABORATORIES, INC., a California corporation ("Grantor").

                                    RECITALS

        A. Bank has agreed to make certain advances of money and to extend
certain financial accommodation to Grantor (the "Loans") in the amounts and
manner set forth in that certain Amended and Restated Loan and Security
Agreement by and between Bank and Grantor dated as of May 15, 2000 (as the same
may be amended, modified or supplemented from time to time, the "Loan
Agreement"; capitalized terms used herein are used as defined in the Loan
Agreement). Bank is willing to make the Loans to Grantor, but only upon the
condition, among others, that Grantor shall grant to Bank a security interest in
certain Copyrights, Trademarks and Patents to secure the obligations of Grantor
under the Loan Agreement.

        B. Pursuant to the terms of the Loan Agreement, Grantor has granted to
Bank a security interest in all of Grantor's right, title and interest, whether
presently existing or hereafter acquired, in, to and under all of the
Collateral.

        NOW, THEREFORE, as collateral security for the prompt and complete
payment when due of its obligations under the Loan Agreement, Grantor hereby
agrees as follows:

                                    AGREEMENT

        To secure its Obligations to Bank under the Loan Agreement, Grantor
grants and pledges to Bank a security interest in all of Grantor's right, title
and interest in, to and under its Intellectual Property Collateral (including
without limitation those Copyrights, Patents and Trademarks listed on Exhibits
A, B and C hereto), and including without limitation all proceeds thereof (such
as, by way of example but not by way of limitation, license royalties and
proceeds of infringement suits), the right to sue for past, present and future
infringements, all rights corresponding thereto throughout the world and all
re-issues, divisions, continuations, renewals, extensions and
continuations-in-part thereof.

        This security interest is granted in conjunction with the security
interest granted to Bank under the Loan Agreement. The rights and remedies of
Bank with respect to the security interest granted hereby are in addition to
those set forth in the Loan Agreement and the other Loan Documents, and those
which are now or hereafter available to Bank as a matter of law or equity. Each
right, power and remedy of Bank provided for herein or in the Loan Agreement or
any of the Loan Documents, or now or hereafter existing at law or in equity
shall be cumulative and concurrent and shall be in addition to every right,
power or remedy provided for herein and the exercise by Bank of any one or more
of the rights, powers or remedies provided for in this Intellectual Property
Security Agreement, the Loan Agreement or any of the other Loan Documents, or
now or hereafter existing at law or in equity, shall not preclude the
simultaneous or later exercise by any person, including Bank, of any or all
other rights, powers or remedies.


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        IN WITNESS WHEREOF, the parties have cause this Intellectual Property
Security Agreement to be duly executed by its officers thereunto duly authorized
as of the first date written above.

                                               GRANTOR:

Address of Grantor:                            PHARMCHEM LABORATORIES, INC.

1505A O'Brien Drive
Menlo Park, CA 94025                           By: /s/ David A. Lattanzio
Attn:  Chief Financial Officer                     ----------------------
                                               Title: Vice President

                                               BANK:

Address of Bank:                               COMERICA BANK-CALIFORNIA
250 Lytton Avenue
Palo Alto, CA  94301
Attn: Jim Weber                                By: James L. Weber
                                                   --------------
                                               Title: VP


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                                    EXHIBIT A

                                   Copyrights

<TABLE>
<CAPTION>
                                Registration/                   Registration/
Description                   Application Number               Application Date
-----------                   ------------------               ----------------
<S>                           <C>                              <C>
                                     NONE
</TABLE>

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                                    EXHIBIT B

                                     Patents

<TABLE>
<CAPTION>
                                Registration/                   Registration/
Description                   Application Number               Application Date
-----------                   ------------------               ----------------
<S>                           <C>                              <C>
                                     NONE
</TABLE>

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                                    EXHIBIT C

                                   Trademarks

<TABLE>
<CAPTION>
                                       Registration/           Registration/
Description                          Application Number       Application Date
-----------                          ------------------       ----------------
<S>                                  <C>                      <C>
PharmScreen(R)                         2,155,538                 May 5, 1998
PharmChek(R)                           2,077,799                July 8, 1997
Premium Comprehensive Management(TM)   75/589122              January 25, 2000
</TABLE>