Interference by sulfinpyrazone and salicylate of aspirin inhibition of platelet cyclooxygenase activity.

The irreversible effect of acetylsalicylic acid on platelet cyclooxygenase activity is inhibited by salicylate and by sulfinpyrazone. Since acetylsalicylate is rapidly hydrolysed in plasma to salicylate which has a relatively prolonged half life in plasma, it is possible that persistant elevation of plasma salicylate may interfere with the efficacy of subsequent doses of aspirin. Sulfinpyrazone is sometimes used in combination with aspirin, and could interfere with the efficacy of aspirin on platelets. This theoretical possibility would be more likely to occur at lower doses of aspirin.