Effectiveness and Safety of Rivaroxaban Versus Warfarin in Obese Nonvalvular Atrial Fibrillation Patients: Analysis of Electronic Health Record Data.

Background: Although rivaroxaban has demonstrated consistent drug levels in normal weight and obese patients, sufficient confirmation of equal clinical effectiveness and safety is currently lacking.Purpose: To evaluate the effectiveness and safety of rivaroxaban versus warfarin for prevention of stroke and systemic embolism (SSE) in obese nonvalvular atrial fibrillation (NVAF) patients.Methods: Using Optum de-identified Electronic Health Record (EHR) data from 11/2011-9/2018,we evaluated NVAF patients with a body mass index (BMI)>/=30 kg/m(2) newly initiated on rivaroxaban or warfarin (index date), with >/=12-months of EHR activity and >/=1 encounter before the index date. We excluded patients with valvular disease or evidence of oral anticoagulant (OAC) use at baseline. Patients who were prescribed rivaroxaban were 1:1 propensity-score matched to patients who were prescribed warfarin (standard differences /=40 kg/m(2)) were performed. Cox regression was performed and reported as hazard ratios (HRs) and 95% confidence intervals (CIs).Results: We included 35,613 rivaroxaban and 35,613 warfarin users with NVAF. Patients were followed for a median of 2.6 years (25%-75% range =1.2-4.1). Rivaroxaban was associated with a reduced risk of SSE (HR =0.83, 95%CI =0.73-0.94) and major bleeding (HR =0.82, 95%CI =0.75-0.89) compared to warfarin. Subanalysis did not show a statistically significant interaction across BMI categories for SSE (p-interaction =0.58) or major bleeding (p-interaction =0.44) outcomes.Conclusions: Among obese NVAF patients, prescription of rivaroxaban was associated with a reduced risk of SSE and major bleeding compared to warfarin, which remained consistent across BMI classes.