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Who should take aspirin for primary prophylaxis of coronary heart disease?

Aspirin is widely used for its analgesic and anti-inflammatory properties, and increasingly in recent years as antithrombotic treatment. Daily doses of 75–150 mg effectively inhibit the ability of blood platelets to synthesise thromboxane A2 and stable prostaglandins during their lifespan in the circulation (7–10 days), resulting in inhibition of platelet function ex vivo (impaired platelet aggregation) and in vivo (prolonged skin bleeding time). Because platelets play an important role in thrombosis, aspirin has an antithrombotic effect.

Systematic reviews of randomised controlled trials of antiplatelet drugs (usually aspirin) have shown clinically worthwhile reductions in cardiovascular events (non-fatal myocardial infarction, stroke, and cardiovascular death) when these agents are used in the treatment of patients with acute ischaemia (myocardial infarction, unstable angina, stroke), when used as secondary prophylaxis in patients with chronic ischaemia (previous myocardial infarction, stroke or transient cerebral ischaemic attacks; stable angina; peripheral arterial disease), and when used as prophylaxis in patients with atrial fibrillation .1 2Antiplatelet treatment (usually with aspirin) is therefore recommended as prophylaxis of cardiovascular disease in these patient groups in national, evidence based guidelines in Scotland3 and the rest of the UK.4 However, as with all effective drugs, aspirin has adverse effects.

True aspirin allergy is rare. As with other non-steroidal anti-inflammatory drugs, inhibition by aspirin of gastrointestinal prostaglandin synthesis commonly causes upper gastrointestinal symptoms including dyspepsia, nausea, and vomiting, peptic ulceration, and bleeding. The risk of a major gastrointestinal bleed is increased by about 1 in 250 patient years, even with low dose or modified release aspirin.5 Inhibition of renal prostaglandin synthesis may also impair renal function, especially in patients with renal artery stenosis and those receiving angiotensin converting enzyme inhibitor treatment. The antiplatelet effect of …