ANTITHROMBOTIC properties of aspirin were first proposed 25 years ago when aspirin was shown to inhibit platelet aggregation and to prolong bleeding time,1-5 but it is only in the past 10 years that the therapeutic benefit of aspirin's antithrombotic properties has been conclusively established by randomized controlled trials.6-14 Early studies used relatively large aspirin doses of approximately 1000 mg, but with increased understanding of the mechanism of its antithrombotic effect, lower-dose regimens were evaluated and were shown to be as effective with less gastrointestinal side effects.7,15,16 Antithrombotic benefit from aspirin has been demonstrated with as little as 75 mg/d for unstable angina,8 160 mg/d for acute myocardial infarction,17 100 mg/d for aortocoronary grafts,18,19 and probably as little as 30 mg/d for minor cerebral ischemic events.16
The trend to use low doses of aspirin increases compliance and reduces gastrointestinal side effects but has the potential