Siguazodan is a selective inhibitor of phosphodiesterase 3. It caused significant increases in cardiac output and stroke volume. It is orally active inotropic/vasodilator agent with a sustained duration in vivo. Siguazodan has potential utility in the treatment of congestive heart failure. Siguazodan has anti-platelet actions over the same concentration range that it is an inotrope and vasodilator. Siguazodan caused bronchodilation. In combination with phosphodiesterase 4, it may be useful in the therapy of asthma.