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                    ADDENDUM TO EQUIPMENT SCHEDULE NO. SG-0 1
                            DATED SEPTEMBER 22, 2000
               TO MASTER LEASE AGREEMENT DATED SEPTEMBER 22, 2000
                    BETWEEN NEOTHERAPEUTICS, INC., AS LESSEE
                  AND COMDISCO LABORATORY AND SCIENTIFIC GROUP
                     a DIVISION OF COMDISCO, INC., AS LESSOR

                       CALIFORNIA CERTIFICATE OF EXEMPTION

NeoTherapeutics, Inc. ("Lessee") certifies that it holds California Seller's
Permit Number ______________. With respect to the machinery and equipment leased
by Comdisco Laboratory and Scientific Group, a division of Comdisco, Inc.
("Lessor") to Lessee on the above referenced Equipment Schedule, Lessee claims
exemption from the payment of California sales or use taxes on the monthly lease
payments for the following reason:

The above referenced lease qualifies as an exempt acquisition sale and leaseback
transaction as defined under California Revenue and Taxation Code Section
6010.65(a) which states that:

        "`Sale' and `purchase' for the purpose of this part, do not include any
        transfer to title to, nor any lease of, tangible personal property
        pursuant to an acquisition sales and leaseback. An acquisition sale and
        leaseback is a sale by a person and leaseback to that person of tangible
        personal property where both of the following conditions are satisfied:

       (1)    That person has paid sales tax reimbursement or use tax with
              respect to that person's purchase of the property.

       (2)    The acquisition sale and leaseback is consummated within 90 days
             of that person's first functional use of the property."

Lessee certifies that it has paid sales tax reimbursement or use tax with
respect to its purchase of tangible property leased under the above referenced
equipment schedule, and agrees to provide evidence of such payment(s) to Lessor.

Based on Lessee's claim for exemption under Section 6010.65, Lessor agrees that
it will not invoice Lessee for use tax on the monthly rental rate.

NEOTHERAPEUTICS, INC.                  COMDISCO LABORATORY AND SCIENTIFIC GROUP,
as Lessee                              A DIVISION OF COMDISCO, INC.
                                       as Lessor

By:                                    By:
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Title:                                 Title:
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Date:                                  Date:
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