Adverse events in low versus normal body weight patients prescribed apixaban for atrial fibrillation

Safety and efficacy of direct oral anticoagulants (DOAC) in low weight patients with atrial fibrillation (AF) is unclear due to few low body weight patients enrolled in clinical trials. To assess bleeding and thrombotic event rates for patients with AF that are prescribed apixaban and have a low versus normal body weight. We analyzed patients with AF prescribed apixaban from 2017 to 2020 with at least 12 months of follow-up. Patients were divided into low [< 60 kg (kg)] and normal (60–100 kg) weight cohorts. Bleeding and thrombotic event rates were compared. Poisson regression and Cox proportional hazard models were used to estimate adjusted adverse event rates. A total of 545 patients met inclusion criteria. In the unadjusted analysis, there was an increase in non-major bleeding events requiring an Emergency Department visit more often in the low versus normal weight cohort (10.8 versus 7.4 per 100 patient-years, p = 0.15). Thrombotic event rates also occurred more often in the lower versus normal weight cohort (2.4 versus 0.9 per 100 patient-years, p = 0.09). However, adjusted analysis found no statistically significant difference in bleeding or thrombotic events between low and normal weight cohorts. The adjusted hazard ratio for bleeding was similar between the two weight cohorts. The use of apixaban in low body weight patients was not associated with higher rates of bleeding or thrombotic events, compared to those with normal body weight, after adjusting for potential confounding covariates. Larger studies may offer further insight into the overall safety and efficacy of DOAC therapy in these patients.