Apixaban vs. Warfarin With Concomitant Aspirin in Patients With Atrial Fibrillation: Insights From the ARISTOTLE Trial

Study Questions:

Does aspirin affect the relative safety and efficacy of apixaban versus warfarin in patients with atrial fibrillation (AF)?


This was a post-hoc analysis of a randomized clinical trial in which apixaban was compared to warfarin in 18,201 patients with AF. The use of aspirin was at the discretion of the treating physician. The median duration of follow-up was 1.8 years.


At the onset of the study, 5,632 patients were taking aspirin, most often at a daily dose of ≤100 mg. Compared to warfarin, apixaban was associated with a significantly lower risk of stroke and systemic embolism among aspirin users (1.12% vs. 1.91%) and nonusers (1.11% vs. 1.32%). Compared to warfarin, apixaban was associated with a significantly lower risk of major bleeding events in aspirin users (3.10% vs. 3.92%) and nonusers (1.82% vs. 2.78%).


The authors concluded that apixaban is more effective and safer than warfarin in patients with AF, regardless of the concomitant use of aspirin.


Although aspirin did not interact with the relative effects of apixaban and warfarin on thromboembolic and major bleeding events, the aspirin users had a higher risk of major hemorrhage than the aspirin nonusers both in the apixaban and warfarin groups. The results indicate that aspirin should be avoided unless necessary (e.g., recent stent placement) regardless of the oral anticoagulant that a patient with AF is receiving. It should be noted that the use of clopidogrel was an exclusion criterion in ARISTOTLE, and no data are available on how this agent affects safety or efficacy of apixaban versus warfarin in aspirin users or nonusers.

Clinical Topics: Anticoagulation Management

Keywords: Warfarin, Embolism

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