For the choice of aspirin dosage, this analysis showed that COX is virtually completely inhibited in platelets, producing an antithrombotic effect, within a few days of beginning 75 mg aspirin daily. It was indicated that high doses of 500–1500 mg aspirin daily (which are more gastrotoxic48) were no more effective than medium doses of 160–325 mg/day or low doses of 75–150 mg/day. Low-dose aspirin (75–150 mg daily) is an effective antiplatelet regimen for long-term use, and the effects of doses lower than 75 mg daily were less certain. In clinical acute settings requiring an immediate antithrombotic effect (such as acute myocardial infarction, acute ischaemic stroke, unstable angina), an initial loading dose of about 150–300 mg aspirin should probably be given