The objective of this review is to summarize data from the Apixaban for 
Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation 
(ARISTOTLE) and Apixaban Versus Acetylsalicylic Acid to Prevent Stroke in Atrial 
Fibrillation Patients Who Have Failed or Are Unsuitable for Vitamin K Antagonist 
Treatment (AVERROES) trials of apixaban for stroke prevention in patients with 
atrial fibrillation (AF). The ARISTOTLE trial compared apixaban with warfarin in 
18 201 patients with AF and ≥ 1 additional risk factor for stroke. The AVERROES 
trial compared apixaban with aspirin in 5599 patients with AF who were at 
increased risk of stroke and for whom vitamin K antagonists were unsuitable. In 
ARISTOTLE, apixaban reduced the risk of stroke or systemic embolism by 21% 
compared with warfarin (1.27% vs 1.60% per year; hazard ratio, 0.79; 95% 
confidence interval, 0.66-0.95). The reduction was significant and demonstrated 
the superiority of apixaban over warfarin for the primary outcome of preventing 
stroke or systemic embolism (P = 0.01 for superiority). Apixaban also reduced 
all-cause mortality by 11% (P = 0.047) and major bleeding by 31% (P < 0.001) 
compared with warfarin. The benefits of apixaban observed in ARISTOTLE are 
further supported by the results from AVERROES, which demonstrated a 55% 
reduction in the risk of stroke or systemic embolism compared with aspirin. Risk 
of major bleeding was not significantly different between apixaban and aspirin. 
Subgroup analyses in both trials demonstrated that the effects of apixaban are 
highly consistent across various patient subpopulations. Discontinuation of 
study medication was significantly lower with apixaban than with either warfarin 
in ARISTOTLE or aspirin in AVERROES. Apixaban is the first new oral 
anticoagulant that has been shown to be superior to warfarin in reducing stroke 
or systemic embolism, all-cause mortality, and major bleeding in patients with 
AF. Moreover, in patients with AF who are considered unsuitable for warfarin 
therapy, apixaban was more effective than aspirin for stroke prevention and had 
a similar rate of major bleeding.