Apixaban (Eliquis) is Substantially More Efficacious Than 325 mg Aspirin for Stroke Prevention
Apixaban reduces the risk of stroke or systemic embolism by 55% compared to aspirin (including 325 mg dosing), with a hazard ratio of 0.45 (95% CI 0.32-0.62, P<0.001), translating to an absolute risk reduction of approximately 2% per year. 1, 2
Magnitude of Benefit
The AVERROES trial directly compared apixaban to aspirin (81-324 mg daily, which includes your 325 mg dose) in patients with atrial fibrillation:
- Stroke/systemic embolism rate: 1.6% per year with apixaban vs. 3.6% per year with aspirin 1, 2
- Absolute risk reduction: ~2% per year
- Number needed to treat: Approximately 50 patients for 1 year to prevent one stroke
This represents a greater than 50% relative risk reduction in the primary outcome of stroke or systemic embolism 3, 2.
Safety Profile Comparison
Critically, this dramatic efficacy advantage comes without increased bleeding risk:
- Major bleeding: 1.4% per year with apixaban vs. 1.2% per year with aspirin (HR 1.13,95% CI 0.74-1.75, P=0.57) 4, 2
- Intracranial bleeding: Actually numerically lower with apixaban (11 cases) vs. aspirin (13 cases) 1, 2
Recent data from the ARCADIA trial further confirms apixaban results in significantly fewer intracranial hemorrhages than aspirin (IRD = -1.4%, 95% CI -2.3% to -0.5%) 5.
Mortality Benefit
Beyond stroke prevention, apixaban showed a trend toward reduced all-cause mortality compared to aspirin (3.5% vs. 4.4% per year, HR 0.79, P=0.07) 2. This mortality benefit becomes even more pronounced in elderly patients ≥85 years, where apixaban demonstrated exceptional efficacy (1% vs. 7.5% per year stroke rate) without increased bleeding 6.
Clinical Context
Current guidelines explicitly state that antiplatelet drugs like aspirin are not an alternative to oral anticoagulation and should not be used for stroke prevention in atrial fibrillation 1. The 2024 ESC guidelines emphasize that aspirin "can lead to potential harm (especially among elderly patients with AF)" 1.
Key Pitfalls to Avoid:
- Never combine aspirin with apixaban for primary prevention: This significantly increases major bleeding (RR 3.15) without reducing ischemic events 7
- Don't use aspirin as a "safer" alternative: The bleeding risk is similar to apixaban while efficacy is dramatically inferior
- Recognize aspirin's limitations: In the ACTIVE-W trial, dual antiplatelet therapy (aspirin + clopidogrel) was still inferior to warfarin, and apixaban outperforms warfarin 1
Bottom Line
Apixaban is approximately twice as effective as 325 mg aspirin for preventing stroke in atrial fibrillation, with equivalent or better safety. The choice between these agents is not a close call—apixaban provides superior protection against the most devastating outcome (stroke) while maintaining a favorable bleeding profile. Aspirin has no role in stroke prevention for patients with atrial fibrillation who are candidates for anticoagulation 1, 3, 4.