The available evidence , predominantly from secondary -prevention observational studies , supports that dosages greater than 75 to 81 mg/d do not enhance efficacy , whereas larger dosages are associated with an increased incidence of bleeding events , primarily related to gastrointestinal tract toxicity .
CONCLUSIONS Currently available clinical data do not support the routine , long-term use of aspirin dosages greater than 75 to 81 mg/d in the setting of cardiovascular disease prevention .
Higher dosages , which may be commonly prescribed , do not better prevent events but are associated with increased risks of gastrointestinal bleeding
CONTEXT More than 50 million US adults take aspirin regularly for long-term prevention of cardiovascular disease , typically either 81 mg/d or 325 mg/d .
Controversy remains regarding the most appropriate long-term daily dose .
OBJECTIVE To review the mechanism of action of aspirin and the clinical literature for relationships among  aspirin dosage , efficacy , and safety .
EVIDENCE SYNTHESIS Although pharmacodynamic data demonstrate that long-term aspirin dosages as low as 30 mg/d are adequate to fully inhibit platelet thromboxane production , dosages as high as 1300 mg/d are approved for use .
The United Kingdom transient ischaemic attack (UK-TIA) aspirin trial: final results.
From 1979 - 85 , 2435 patients with a transient ischaemic attack or minor ischaemic stroke were r and omly allocated to receive long term " blind " treatment with aspirin 600 mg twice daily ( n = 815 ) , aspirin 300 mg once daily ( n = 806 ) or placebo ( n = 814 ) . No patient was lost to follow up . The " intention to treat " comparison included all the serious vascular events and deaths which occurred before the end of the follow up period on 30 September 1986 . There was no difference in efficacy between the 300 mg and 1200 mg daily doses of aspirin , but the lower dose was undoubtedly less gastrotoxic . Also , there was no definite difference in the response of  males and females to aspirin . The odds of suffering a major stroke , myocardial infa rct ion or vascular death were 15 % less in the combined aspirin groups compared with the placebo group ( 95 % confidence interval 29 % reduction to 3 % increase in odds ) which is compatible with the continuing overview of all the similar trials of antiplatelet drugs where the relative reduction in odds was 25 % . There was no statistically significant reduction in the likelihood of either disabling major stroke and vascular death or vascular death occurring
The available evidence , predominantly from secondary -prevention observational studies , supports that dosages greater than 75 to 81 mg/d do not enhance efficacy , whereas larger dosages are associated with an increased incidence of bleeding events , primarily related to gastrointestinal tract toxicity .
CONCLUSIONS Currently available clinical data do not support the routine , long-term use of aspirin dosages greater than 75 to 81 mg/d in the setting of cardiovascular disease prevention .
Higher dosages , which may be commonly prescribed , do not better prevent events but are associated with increased risks of gastrointestinal bleeding
CONTEXT More than 50 million US adults take aspirin regularly for long-term prevention of cardiovascular disease , typically either 81 mg/d or 325 mg/d .
Controversy remains regarding the most appropriate long-term daily dose .
OBJECTIVE To review the mechanism of action of aspirin and the clinical literature for relationships among  aspirin dosage , efficacy , and safety .
EVIDENCE SYNTHESIS Although pharmacodynamic data demonstrate that long-term aspirin dosages as low as 30 mg/d are adequate to fully inhibit platelet thromboxane production , dosages as high as 1300 mg/d are approved for use .