His discovery led to abandonment of long acting digitalis drugs like digitoxin. Dosages of theophylline, digitoxin, and medroxyprogesterone acetate may need to be increased. The name is derived from that of digitoxin, which explains its pronunciation. At this point the similarities between digitoxin and calotropin end. Other products from Merck include Metformin, Bisoprolol, Levothyroxine and Digitoxin. Digitoxigenin, a cardenolide, is the aglycone of digitoxin. It is an acetyl derivative of digitoxin, found in the leaves of "Digitalis" species.