Summary
Various cardiovascular drugs such as nitrates and propranolol, used in the treatment
of coronary artery disease have been shown to have an antiplatelet effect. We have
studied the in vitro effects of two antiarrhythmic drugs, verapamil and disopyramide,
and have shown their inhibitory effect on platelet function. Verapamil, a calcium
channel blocker, inhibited the second phase of platelet aggregation induced by adenosine
diphosphate (ADP) and inhibited aggregation induced by collagen. Disopyramide similarly
inhibited the second phase of platelet aggregation caused by ADP and aggregation induced
by collagen. Either drug in synergism with propranolol inhibited ADP or collagen-induced
platelet aggregation. Disopyramide at high concentrations inhibited arachidonic add
whereas verapamil was without effect. Verapamil, but not disopyramide, inhibited aggregation
induced by the ionophore A23187.
Key words
Platelet inhibition - Verapamil - Disopyramide - Propranolol