Background and purpose: Comparative effectiveness and safety of oral anticoagulants in patients with atrial fibrillation and high polypharmacy are unknown.
Methods: We used Medicare administrative data to evaluate patients with new atrial fibrillation diagnosis from 2015 to 2017, who initiated an oral anticoagulant within 90 days of diagnosis. Patients taking ≤3, 4 to 8, or ≥9 other prescription medications were categorized as having low, moderate, or high polypharmacy, respectively. Within polypharmacy categories, patients receiving apixaban 5 mg twice daily, rivaroxaban 20 mg once daily, or warfarin were matched using a 3-way propensity score matching. Study outcomes included ischemic stroke, bleeding, and all-cause mortality.
Results: The study cohort included 6985 patients using apixaban, 3838 using rivaroxaban, and 6639 using warfarin. In the propensity-matched cohorts there was no difference in risk of ischemic stroke between the 3 drugs in patients with low and moderate polypharmacy. However, among patients with high polypharmacy, the risk of ischemic stroke was higher with apixaban compared with warfarin (adjusted hazard ratio 2.34 [95% CI, 1.01-5.42]; P=0.05) and similar to rivaroxaban (adjusted hazard ratio, 1.38 [95% CI, 0.67-2.84]; P=0.4). There was no difference in risk of death between the 3 drugs in patients with low and moderate polypharmacy, but apixaban was associated with a higher risk of death compared with rivaroxaban (adjusted hazard ratio, 2.03 [95% CI, 1.01-4.08]; P=0.05) in the high polypharmacy group. Apixaban had lower bleeding risk compared with warfarin in the low polypharmacy group (adjusted hazard ratio, 0.54 [95% CI, 0.32-0.90]; P=0.02), but there was no difference in bleeding between the 3 drugs in the moderate and high polypharmacy groups.
Conclusions: Our study suggests that among patients with significant polypharmacy (>8 drugs), there may be a higher stroke and mortality risk with apixaban compared with warfarin and rivaroxaban. However, differences were of borderline significance.
Keywords: atrial fibrillation; polypharmacy; warfarin.