Antiplatelet drugs in secondary prevention after acute myocardial infarction.

Abstract

Clopidogrel, a new ADP receptor antagonist, selectively and irreversibly inhibits ADP-induced platelet activation and aggregation thereby preventing atherothrombosis. Clopidogrel 75 mg o.d. and aspirin 325 mg o.d. were compared in the CAPRIE trial, a prospective international multicenter double-blind trial conducted in 19,185 high- risk patients with symptomatic atherosclerotic disease. Qualifying events for inclusion into the trial were ischemic stroke (IS) within the past six months, myocardial infarction (MI) within the past 35 days or peripheral arterial disease. Duration of treatment was one to three years. The primary efficacy end point was a composite cluster of IS, MI of vascular death. Overall, clopidogrel provided an 8.7% relative risk reduction (p = 0.043) in the occurrence of a first event of the cluster over and above aspirin and a favorable trend on each of the components of the primary end point. The greatest relative risk reduction was noted for prevention of MI (19.2%). In terms of number of events prevented per 1,000 patients and per year, clopidogrel is expected to prevent 24 major atherothrombotic events versus 19 with aspirin. Clopidogrel shows a favorable safety profile with fewer cases of gastrointestinal bleeding and better gastric tolerability.