Antiplatelet drugs.

Antiplatelet drugs protect against myocardial infarction, stroke, cardiovascular death and other serious vascular events in patients with a history of previous vascular events or known risk factors for cardiovascular disease. Aspirin reduces the risk of serious vascular events in patients at high risk of such an event by about a quarter and is recommended as the first-line antiplatelet drug. Clopidogrel reduces the risk of serious vascular events among high-risk patients by about 10% compared with aspirin. It is as safe as aspirin, but much more expensive. It is an appropriate alternative to aspirin for long-term secondary prevention in patients who cannot tolerate aspirin, have experienced a recurrent vascular event while taking aspirin, or are at very high risk of a vascular event (>/= 20% per year). Addition of clopidogrel to aspirin reduces the risk of serious vascular events among patients with non-ST-segment elevation acute coronary syndromes by 20%, and patients undergoing percutaneous coronary intervention by 30%, compared with aspirin alone. Addition of a glycoprotein IIb/IIIa receptor antagonist to aspirin reduces the risk of vascular events among patients with non-ST-segment elevation acute coronary syndromes by 10% and among patients undergoing percutaneous coronary intervention by 30%, compared with aspirin alone; it appears to provide incremental benefit in patients also treated with clopidogrel. Addition of dipyridamole to aspirin seems to be more effective than aspirin alone for preventing recurrent stroke, but its overall effect in preventing serious vascular events in patients with ischaemic stroke and transient ischaemic attack has not been determined.