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 .
Low-dose and high-dose acetylsalicylic acid for patients undergoing carotid endarterectomy: a randomised controlled trial
BACKGROUND Endarterectomy benefits certain patients with carotid stenosis , but benefits are lessened by perioperative surgical risk . Acetylsalicylic acid lowers the risk of stroke in patients who have experienced transient ischaemic attack and stroke . We investigated appropriate doses and the role of acetylsalicylic acid in patients undergoing carotid endarterectomy . METHODS In a r and omised , double-blind , controlled trial , 2849 patients scheduled for endarterectomy were r and omly assigned 81 mg ( n=709 ) , 325 mg ( n=708 ) , 650 mg ( n=715 ) , or 1300 mg ( n=717 ) acetylsalicylic acid daily , started before surgery and continued for 3 months . We recorded occurrences of stroke , myocardial infa rct ion , and death . We compared patients on the two higher doses of acetylsalicylic acid with patients on the two lower doses . FINDINGS Surgery was cancelled in 45 patients , none were lost to follow-up by 30 days , and two were lost by 3 months . The combined rate of stroke , myocardial infa rct ion , and death was lower in the low-dose groups than in the high-dose groups at 30 days ( 5.4 vs 7.0 % , p=0.07 ) and at 3 months ( 6.2 vs 8.4 % , p=0.03 ) . In an efficacy analysis , which excluded patients taking 650 mg or more acetylsalicylic acid before r and omisation , and patients r and omised within 1 day of surgery , combined rates were 3.7 % and 8.2 % , respectively , at 30 days ( p=0.002 ) and 4.2 % and 10.0 % at 3 months ( p=0.0002 ) . INTERPRETATION The risk of stroke , myocardial infa rct ion , and death within 30 days and 3 months of endarterectomy is lower for patients taking 81 mg or 325 mg acetylsalicylic acid daily than for those taking 650 mg or 1300 mg
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 .