<PAGE>

                                                                  EXHIBIT 10.32

                                SECOND AMENDMENT TO

                 MOLECULAR BIOSYSTEMS, INC. 1993 STOCK OPTION PLAN



The Molecular Biosystems, Inc. 1993 Stock Option Plan, as amended (the "Plan"),
is amended as follows pursuant to the authority of the Board of Directors of
Molecular Biosystems, Inc. under Paragraph 8.2 of the Plan:

1.    PARAGRAPH 2.1A.  The following provision is added as Paragraph 2.1a of 
the Plan:

2.1a  CHANGE OF CONTROL means an event or the last of a series of related 
events by which:

(1)   any Person directly or indirectly acquires or otherwise becomes 
entitled to vote 25% or more of the Company's Common Stock (or, if in the 
future the Company has more than one class of stock outstanding, any Person 
directly or indirectly acquires or otherwise becomes entitled to vote stock 
having 25% or more of the voting power in elections for Directors); or

(2)   during any 24-month period a majority of the members of the Board of 
Directors ceases to consist of Directors who were:

(a)   Directors at the beginning of the period ("Continuing Directors"); or

(b)   appointed to office after the start of the period by the Board of 
Directors with the approval of two-thirds of the incumbent Continuing 
Directors ("Appointed Directors"); or

(c)   elected to office after the start of the period by the Company's 
stockholders following nomination for election by the Board of Directors with 
the approval of two-thirds of the incumbent Continuing Directors ("Elected 
Directors"); or

(d)   appointed to office after the start of the period by the Board of 
Directors with the approval of two-thirds of the incumbent Continuing, 
Appointed and Elected Directors; or

(e)   elected to office after the start of the period by the Company's 
stockholders following nomination for election by the Board of Directors with 
the approval of two-thirds of the incumbent Continuing, Appointed and Elected 
Directors; or

(3)   the Company merges or consolidates with another corporation, and 
holders of outstanding shares of the Company's Common Stock immediately prior 
to the merger or consolidation do not own stock in the survivor of the merger 
or consolidation having more than 75% of the voting power in elections for 
directors; or

                                      -1-

<PAGE>


(4)   the Company sells all or a substantial portion of the consolidated 
assets of the Company and its Subsidiaries, and the Company does not own 
stock in the purchaser having more than 75% of the voting power in elections 
for directors.

As used in this Paragraph 2.1a, a "Person" means any "person" as that term is 
used in sections 13(d) and 14(d) of the Securities Exchange Act of 1934, as 
amended, together with all of that person's "affiliates" and "associates" as 
those terms are defined in Rule 12b-2 of the Securities and Exchange 
Commission.

2.    PARAGRAPH 6.2.  Paragraph 6.2 of the Plan is amended to read as follows:

6.2   TERM. The Plan Committee shall determine (i) whether each Option shall 
be exercisable in full at one time or in installments at different times and 
(ii) the time or times at which the Option or Installments shall become and 
remain exercisable. No Option or Installment shall be exercisable prior to 
the first anniversary of the Grant Date (except as its exercisability is 
accelerated by reason of a Change in Control or by action of the Plan 
Committee) or have an Expiration Date later than the tenth anniversary of the 
Grant Date.

Notwithstanding any limitation on exercisability in Paragraph 6.6 or anything 
to the contrary in the underlying Option Agreement, each outstanding Option 
or Installment shall become exercisable in full upon a Change in Control. In 
addition, the Plan Committee, in its discretion, may accelerate the 
exercisability of any Option or Installment at any time under any related or 
other circumstances.

3.    EFFECTIVE DATE.  This Amendment shall become effective as of the date 
of its approval by the Board of Directors of Molecular Biosystems, Inc.

                                      -2-