Effects of verapamil on platelet aggregation and serum thromboxane synthesis in vitro and in vivo.

The aim of this study was to evaluate the in vitro effects of verapamil on platelet aggregation and serum thromboxane formation. We also studied the in vivo effects of verapamil retard on platelet aggregation and serum thromboxane formation. The incubation of verapamil with PRP produced a dose-dependent decrease of in vitro platelet aggregation for all the agents used. Potentiation by verapamil of antiaggregating activity of prostacyclin was also demonstrated; in fact when verapamil and prostacyclin were added simultaneously a synergistic inhibition of platelet aggregation by ADP was observed. In whole blood verapamil partially inhibited thromboxane production only at a higher concentration. In vivo verapamil significantly decreased platelet aggregation induced by ADP and epinephrine while no changes were observed after arachidonic acid. No significant changes occurred in serum TXB2 levels. The observations suggest a potential role for verapamil in antithrombotic therapy as an antiplatelet agent.