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/m 2 . 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/m 2 ) 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.