
<PAGE>   1
                                 FIRST AMENDMENT

                             TO SECURITY AGREEMENT,
            INTELLECTUAL PROPERTY SECURITY AGREEMENT AND ASSIGNMENT,

                         LICENSE AGREEMENT, AND GUARANTY

         This First Amendment to Security Agreement, Intellectual Property
Security Agreement and Assignment, License Agreement, and Guaranty (this "First
Amendment") dated as of February 9, 1996, is entered into between Neuromed,
Inc., a Florida corporation ("Neuromed"), and NationsBank of Texas, N.A.
("Lender").

                                   BACKGROUND.

         Quest Medical, Inc. ("Borrower"), and Lender have entered into the
First Amended and Restated Credit Agreement, dated as of March 31, 1995 (the
"Existing Credit Agreement"). Pursuant to the Existing Credit Agreement,
Neuromed executed the Security Agreement dated as of March 31, 1995 (the
"Existing Security Agreement"), the Intellectual Property Security Agreement and
Assignment dated as of March 31, 1995 (the "IP Agreement"), the License
Agreement dated as of March 31, 1995 (the "License Agreement") and the Guaranty
dated as of March 31, 1995 (the "Guaranty"). Borrower and Lender have entered
into the Second Amended and Restated Credit Agreement dated as of February 9,
1996 (the "Credit Agreement"), which restates in its entirety the Existing
Credit Agreement.

         It is a condition precedent to the effectiveness of the Credit
Agreement that Neuromed shall have executed and delivered this First Amendment.

                                   AGREEMENT.

         NOW, THEREFORE, in consideration of the covenants, conditions and
agreements hereafter set forth, and for other good and valuable consideration,
the receipt and adequacy of which are all hereby acknowledged, Neuromed and
Lender covenant and agree as follows:

1. Defined Terms. Capitalized terms used herein and not otherwise defined herein
have the meaning given to them in the Credit Agreement.

2. Amendments to Security Agreement. The Security Agreement is amended as
follows:

         (a) Paragraphs (1) and (2) of the Background section are deleted in
their entirety and the following is substituted in lieu thereof:
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                  (1) Secured Party and Quest Medical, Inc., a Texas corporation
         ("Borrower") have entered into the First Amended and Restated Credit
         Agreement dated as of March 31, 1995 (as amended, the "Existing Credit
         Agreement"), pursuant to which Debtor and Secured Party entered into
         the Security Agreement dated as of March 31, 1995 ("Security
         Agreement") and related agreements.

                  (2) Secured Party and Borrower have entered into the Second
         Amended and Restated Credit Agreement dated as of February 9, 1996
         (such agreement, together with all amendments and restatements thereof,
         the "Credit Agreement") which restates in its entirety the Existing
         Credit Agreement.

         (b) Section 1.4 is amended by deleting "(if the security is subject to
Brokerage Agreement and the Brokerage Agreement permits such issuance)."

         (c) The last sentence of Section 3.3 is amended by deleting "Section
4.2, 5.5, 5.6, 5.9, 5.10 or 5.12" and substituting, in lieu thereof, "Section
4.2, 5.5, 5.6, 5.7 or 5.9."

         (d) Section 3.4(a) is amended by deleting the second sentence.

         (e) Section 3.4(b) is amended by deleting the two references to
"Section 4.2, 5.5, 5.6, 5.9, 5.10 or 5.12" and substituting, in lieu of both,
"Section 4.2, 5.5, 5.6, 5.7 or 5.9."

         (f) Section 3.5 is amended by deleting the third and fourth sentences.

         (g) The subject heading and text of Section 3.6 are deleted in their
entirety and "[Intentionally Omitted]" is substituted in lieu thereof.

         (h) Section 3.7 is amended by deleting from the second sentence "Except
for any property maintained in a Brokerage Account, if" and substituting "If" in
lieu thereof.

         (i) Section 3.8 is amended by deleting "each party to a Brokerage
Agreement and."

3. Amendments to IP Agreement. The IP Agreement is amended by deleting Paragraph
(1) of the Background section in its entirety and substituting the following in
lieu thereof:

                  (1) Secured Party and Quest Medical, Inc., a Texas corporation
         ("Borrower"), have entered into the First Amended and Restated Credit
         Agreement dated as of March 31, 1995 (such agreement, together with all
         amendments and 

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         restatements thereof, the "Existing Credit Agreement"), and the Second
         Amended and Restated Credit Agreement dated as of February 9, 1996
         (such agreement, together with all amendments and restatements thereof,
         the "Credit Agreement"). The Credit Agreement restates in its entirety
         the Existing Credit Agreement.

4. Amendments to License Agreement. The License Agreement is amended by deleting
the second "WHEREAS" paragraph in its entirety and substituting the following in
lieu thereof:

                  WHEREAS, Licensee and Quest Medical, Inc., a Texas corporation
         ("Borrower"), have entered into the First Amended and Restated Credit
         Agreement dated as of March 31, 1995 (such agreement, together with all
         amendments and restatements thereof, the "Existing Credit Agreement");

                  WHEREAS, Licensee and Licensor have entered into the Second
         Amended and Restated Credit Agreement dated as of February 9, 1996
         (such agreement, together with all amendments and restatements thereof,
         the "Credit Agreement");

                  WHEREAS, the Credit Agreement restates in its entirety the
         Existing Credit Agreement;

5. Amendments to Guaranty. The Guaranty is amended by deleting the initial
paragraph in its entirety and substituting the following in lieu thereof:

                  THIS GUARANTY is entered into as of this 31st day of March,
         1995 by Neuromed, Inc., a Florida corporation ("Guarantor"), in favor
         of NationsBank of Texas, N.A. ("Lender") under the First Amended and
         Restated Credit Agreement dated as of March 31, 1995 (such agreement,
         together with all amendments and restatements thereof, the "Existing
         Credit Agreement"), between Quest Medical, Inc. ("Borrower") and
         Lender, as restated in its entirety by the Second Amended and Restated
         Credit Agreement dated as of February 9, 1996 (such agreement, together
         with all amendments and restatements thereof, the "Credit Agreement"),
         between Borrower and Lender.

6. Representations and Warranties of Neuromed. Neuromed represents and warrants
to Lender that, as of the date hereof and after giving effect to the amendments
in Sections 2, 3, 4, and 5:

         (a) The representations and warranties contained in each of the
Security Agreement, the IP Agreement, the License Agreement, and the Guaranty
are true and correct in all material respects on and as of the date hereof as
though made on and as of the date hereof, except for such representations and
warranties which relate to a particular date.

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         (b) Neuromed has full power and authority to execute, deliver and
perform this First Amendment, and this First Amendment constitutes the legal,
valid and binding obligation of Neuromed, enforceable in accordance with its
terms.

         (c) No authorization, approval, consent or other action by, notice to,
or filing with, any Tribunal or other Person, is required for the execution,
delivery or performance by Neuromed of this First Amendment.

         Conditions of Effectiveness. This First Amendment shall be effective on
the date all conditions precedent to the initial Advance under Section 3.1 of
the Credit Agreement have occurred or exist.

8. Reference to the Security Agreement, the IP Agreement, the License Agreement
and the Guaranty.

         (a) Upon the effectiveness of this First Amendment, each reference in
the Security Agreement, the IP Agreement, the License Agreement, and the
Guaranty, respectively, to "this Agreement", "hereunder", or words of like
import shall mean and be a reference to the Security Agreement, the IP
Agreement, the License Agreement, and the Guaranty, respectively, as affected
and amended hereby.

         (b) The Security Agreement, the IP Agreement, the License Agreement,
and the Guaranty, as affected by the amendments referred to above, shall remain
in full force and effect and are hereby ratified and confirmed.

         (c) THE SECURITY AGREEMENT, THE IP AGREEMENT, THE LICENSE AGREEMENT,
AND THE GUARANTY, AS AFFECTED BY THE AMENDMENTS CONTAINED IN THIS FIRST
AMENDMENT, TOGETHER WITH EACH OTHER LOAN PAPER, REPRESENT THE FINAL AGREEMENT
AMONG THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,
CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO
UNWRITTEN ORAL AGREEMENTS AMONG THE PARTIES.

9. Execution in Counterparts. This First Amendment may be executed in any number
of counterparts and by different parties hereto in separate counterparts, each
of which when so executed and delivered shall be deemed to be an original and
all of which taken together shall constitute but one and the same instrument.

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10. Governing Law; Binding Effect. This First Amendment shall be governed by and
construed in accordance with the laws of the State of Texas and be binding upon
Neuromed and Lender and their respective successors and assigns.

11. Headings. Section headings in this First Amendment are included herein for
convenience of reference only and shall not constitute part of this First
Amendment for any other purpose.

         IN WITNESS WHEREOF, the parties hereto have executed this First
Amendment as of the date first above written.

                                  NEUROMED, INC.

                                  By:
                                     ------------------------------------------
                                  F. Robert Merrill III, Vice President

                                  NATIONSBANK OF TEXAS, N.A.

                                  By:
                                     ------------------------------------------
                                     Brian K. Schneider, Vice President

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