Exhibit 4.1


                               First Amendment to

                Molecular Biosystems, Inc. 1993 Stock Option Plan



       The first sentence of Paragraph 3.2 ("Maximum  Number of Options") of the
  Molecular  Biosystems,  Inc.  1993  Stock  Option  Plan is  amended to read as
  follows:

           The maximum number of shares of Common Stock for which Options may be
           granted is 3,250,000  (subject to adjustment as provided in Paragraph
           8.1).