The prolonged effect of sulfinpyrazone on collagen-induced platelet aggregation in vivo

The relationship between the concentration of sulfinpyrazone circulating in the plasma and its effects on platelet function invivo is not well understood. We have studied the relationship between inhibition of invivo collagen-induced platelet aggregation and the sulfinpyrazone plasma concentration. Sulfinpyrazone was shown to inhibit invivo collagen-induced platelet aggregation in a dose-related manner and the inhibitory effects were directly related to the concentration of sulfinpyrazone in the plasma. In addition, with high doses, platelet aggregation invivo was inhibited for up to 18 hours after drug administration which was 14 hours after the sulfinpyrazone had been cleared from the plasma. These data suggest that a previously unidentified sulfinpyrazone metabolite is formed invivo which exerts a potent inhibitory effect on platelet function.