Ticlopidine - an antiplatelet drug: effects in human volunteers.

Abstract

Ticlopidine, 500–1000mg daily, was given to 7 healthy volunteers for 5 to 6 days. By the 5th day the bleeding time was significantly prolonged, on average from 3.9 to 11 min and primary aggregation of platelets induced by ADP as well as collagen-induced aggregation were significantly decreased; that induced by thrombin and serotonin was decreased at least in some individuals. Maximal stimulation of platelets in plasma by thrombin caused a two-fold increase in malondialdehyde production and the Stypven clotting time was significantly prolonged. The heparin thrombin clotting time may also have been prolonged. The degree of inhibition was dependent on the strength of the aggregating agent. After stopping the drug the effects persisted for 4 to 8 days. The response to the drug varied considerably between different individuals. It is postulated that this drug may alter the platelet membrane, thereby blocking a number of receptor sites and that its mechanism is independent of inhibition of prostaglandin metabolism.