Efficacy and safety of factor Xa inhibitors in low body weight patients

Study Objective: The purpose of this study is to provide evidence for the safety and efficacy of factor Xa inhibitors in patients with a weight <= 60 kg or BMI < 18.5 kg/m2.Design: Multicenter, retrospective, cohort study.Setting: Twenty-two Ascension Health hospitals.Patients: Low-body-weight adult patients (weight <= 60 kg or BMI < 18.5 kg/m2) receiving treatment for atrial fibrillation or venous thromboembolism.Intervention: Factor Xa inhibitors (apixaban or rivaroxaban) or warfarin.Measurements and Main Results: This study included 2538 patients between the factor Xa inhibitors (n = 1695) and warfarin (n = 843) groups with a mean weight of 53.5 +/- 5.5 kg and BMI of 20.7 +/- 3.1 kg/m(2). No significant difference in time to major bleeding was noted after controlling for potential confounders (HR 1.03, 95% CI 0.70-1.53, p = 0.87); similar results were seen following propensity score matching. Thromboembolism (5.3% vs. 6.2%, p = 0.38), composite major + clinically relevant nonmajor bleeding (9.8% vs. 11.5%, p = 0.18), and all-cause mortality (10.7% vs. 12.8%, p = 0.12) were similar between patients receiving factor Xa inhibitors versus warfarin.Conclusion: No differences in safety or effectiveness were noted between factor Xa inhibitors versus warfarin. These findings provide encouraging evidence to support the use of factor Xa inhibitors in low-body-weight patients.