What is the optimal dose of ASA for risk reduction in atherosclerotic CV disease?

Acetylsalicylic acid (ASA) is recommended in patients with established atherosclerotic cardiovascular (CV) disease to lower the risk of adverse health outcomes, including death, myocardial infarction and stroke.However, the preferred dosage of ASA in this situation is uncertain. Some studies have suggested different risks and benefits depending on whether ASA 81 mg/d or 325 mg/d is used. In addition, it's unclear whether these different doses affect ASA’s side-effect profile, including the frequency of major bleeding or discontinuation due to minor bleeding or dyspepsia.To examine this issue, a new U.S. study, using a “real-world” open-label, multicentre design, randomly assigned patients with established atherosclerotic CV disease to receive ASA 81 mg or 325 mg per day. The primary effectiveness outcome was a composite of death from any cause, hospitalization for myocardial infarction or hospitalization for stroke, assessed in a time-to-event analysis. The primary safety outcome was hospitalization for major bleeding, also assessed in a time-to-event analysis.The investigators followed a total of 15,076 patients for a median of 26.2 months. Before randomization, 13,537 patients were already taking ASA, and 85.3% of these patients had been taking 81 mg/d. Death, hospitalization for myocardial infarction or hospitalization for stroke occurred in 590 patients (7.28%) in the 81 mg ASA group and 569 patients (7.51%) in the 325 mg ASA group (hazard ratio, 1.02; 95% confidence interval [CI], 0.91–1.14). Hospitalization for major bleeding occurred in 53 patients (0.63%) in the 81 mg ASA group and 44 patients (0.60%) in the 325 mg ASA group (hazard ratio, 1.18; 95% CI, 0.79–1.77).Patients assigned to 325 mg ASA had a higher frequency of dose switching than those assigned to 81 mg ASA (41.6% vs. 7.1%) and discontinued ASA more frequently (11.1% vs 7.0%).The authors conclude that in this trial involving patients with established CV disease, no significant differences in effectiveness or safety outcomes were seen between patients assigned to ASA 81 mg versus ASA 325 mg daily. In addition, long-term adherence was better with the 81 mg ASA dosing strategy, as there was substantial dose switching from ASA 325 mg/d to 81 mg/d. Reference Jones WS, Mulder H, Wruck LM, et al; for the ADAPTABLE Team. Comparative effectiveness of aspirin dosing in cardiovascular disease. N Engl J Med 2021;384:1981-90. DOI: 10.1056/NEJMoa2102137.

What is the optimal dose of ASA for risk reduction in atherosclerotic CV disease?

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