OBJECTIVE: The Apixaban for Reduction in Stroke and Other Thromboembolic Events 
in Atrial Fibrillation (ARISTOTLE) trial demonstrated that apixaban was 
effective in reducing the risk of stroke and major bleeding in non-valvular 
atrial fibrillation (NVAF) patients. Medical cost avoidance studies for oral 
anticoagulants have used warfarin event rates from clinical trials, which may 
not reflect the real-world (RW) setting. This study aimed to estimate the 
difference in medical costs associated with apixaban instead of warfarin in RW 
NVAF patients.
METHODS: This study selected patients with NVAF diagnosis during 2007-2010 from 
a Medco population of US commercial and Medicare health plans. Stroke and major 
bleeding excluding intracranial hemorrhage (MBEIH) were identified using 
diagnosis codes. Pharmacy claims were used to define warfarin exposure periods. 
Rates of stroke and MBEIH were calculated during warfarin exposure. To estimate 
the absolute risk reduction (ARR) between warfarin and apixaban in RW, the 
relative risk reductions (RRR) from ARISTOTLE were multiplied by the event rates 
observed in RW during warfarin exposure. Medical cost reductions associated with 
apixaban were calculated by applying the ARR to the 1-year incremental cost for 
each event. Stroke and MBEIH costs were obtained from the literature and 
adjusted to 2011 levels.
RESULTS: During a patient year, the use of apixaban instead of warfarin resulted 
in medical cost reductions of $493 for stroke and $752 for MBEIH and $1245 for 
the combined outcome of both events. The medical costs avoided were greater as 
baseline stroke risk increased.
CONCLUSION: If RRRs demonstrated in ARISTOTLE persist in RW, the use of apixaban 
will be associated with lower medical costs vs warfarin. Main limitations of 
this study were: identification of clinical events using administrative codes 
rather than confirmatory clinical data, inability to evaluate the level of 
international normalized ratio (INR) control, and not including INR monitoring 
and drug costs.