A systematic review1 including 11 studies (8 RCTs and 3 observational studies) reviewed the mechanism of action of aspirin and the clinical literature for the relationships among aspirin dosage, efficacy, and safety. The narrative evidence synthesis concludes that 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. In the United States, 81 mg/d of aspirin is prescribed most commonly (60%), followed by 325 mg/d (35%). 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.
Primary/Secondary Keywords