<PAGE>   1
                                                                     Exhibit 4.1

                               AMENDMENT AGREEMENT

                  AMENDMENT AGREEMENT dated as of November 12, 1996, between
Medex, Inc., an Ohio corporation (the "Company"), and The Huntington National
Bank (the "Rights Agent").

                  WHEREAS, the Company and the Rights Agent have heretofore
executed and entered into a Rights Agreement dated as of October 12, 1996,
between the Company and the Rights Agent (the "Rights Agreement"), setting forth
the terms of the Company's common share purchase Rights (as defined in the
Rights Agreement);

                  WHEREAS, the Company and the Rights Agent may from time to
time supplement or amend the Rights Agreement pursuant to the provisions of
Section 26 of the Rights Agreement; and

                  WHEREAS, all acts and things necessary to make this Amendment
Agreement a valid, legal and binding instrument of the Company and the Rights
Agent have been duly done, performed and fulfilled, and the execution and
delivery hereof by each of the Company and the Rights Agent have been in all
respects duly authorized by the Company and the Rights Agent, respectively.

                  NOW, THEREFORE, the Company and the Rights Agent hereby agree
as follows:

                  1. Pursuant to Section 26 of the Rights Agreement, Section 
1(c) of the Rights Agreement is hereby amended to add the following sentence at
the end of such Section:

                  "The foregoing notwithstanding, neither Furon Company
         ("Purchaser") nor any of its Affiliates or Associates shall be deemed
         to be the "Beneficial Owner" of, or to "beneficially own," any
         securities which such Person may, directly or indirectly, acquire or
         have the right to vote or dispose of, or may be deemed to have the
         right to acquire, to vote or to dispose of, as a result of the
         transactions contemplated by that certain Agreement and Plan of Merger
         among Purchaser, Furon Company and the Company (the "Merger
         Agreement"), including without limitation (A) securities acquired as a
         result of the "Offer" and the "Merger" (as such terms are defined in
         the Merger Agreement), (B) securities acquired from officers and
         directors of the Company as contemplated by Section (6.16) of the
         Merger Agreement and (C) securities acquired pursuant to the Company
         Option Agreement contemplated by Section (6.18) of the Agreement."

                  2. This Amendment Agreement may be executed in any number of
counterparts, each of which shall be an original, and such counterparts shall
together constitute but one and the same instrument. Terms not defined herein
shall, unless the context otherwise requires, have the meanings assigned to such
terms in the Rights Agreement.
<PAGE>   2
                  3. In all respects not inconsistent with the terms and
provisions of this Amendment Agreement, the Rights Agreement is hereby ratified
and confirmed. In executing and delivering this Amendment Agreement, the Rights
Agent shall be entitled to all of the privileges and immunities afforded to the
Rights Agent under the terms and conditions of the Rights Agreement.

                  IN WITNESS WHEREOF, the parties hereto have caused this
Amendment Agreement to be duly executed and their respective corporate seals to
be hereunto affixed and attested, all as of the day and year first above
written.

Attest:                            MEDEX, INC.

/s/                                By:/s/ Bradley P. Gould

--------------------------            --------------------------------
Name:                              Name: Bradley P. Gould
Title:                             Title: President and CEO

Attest:                            THE HUNTINGTON NATIONAL BANK

/s/                                By:/s/ Mark A. Dunn

--------------------------            ----------------------------------
Name:                              Name: Mark A. Dunn
Title:                             Title:  Trust Officer