Prevalence and factors associated with inappropriate dosing of apixaban and rivaroxaban in hospitalized older adults with atrial fibrillation: a cross-sectional study.

INTRODUCTION: Atrial fibrillation (AF) is a common condition among older adults, requiring anticoagulation therapy to prevent thromboembolic events. Direct oral anticoagulants (DOACs) are now recommended as first-line therapy for this purpose. Apixaban and rivaroxaban are two direct-factor Xa inhibitors whose dosing is based on various factors (age, weight, creatinine, and creatinine clearance) that can affect the pharmacokinetics of the medication. This study aimed to evaluate factors associated with inappropriate dosing of apixaban or rivaroxaban based on the summary of product characteristics.

METHODS: A retrospective, single-center study included 777 hospitalizations of patients treated with apixaban or rivaroxaban for AF between 1 January 2018 and 31 December 2022. Primary endpoint assessed whether the dose of apixaban or rivaroxaban was within the summary of product characteristics used by European Medicine Agency (EMA).

RESULTS: Inappropriate dosing of apixaban or rivaroxaban is noted for approximately 30% of hospitalizations mostly underdosing. Factors associated with the risk of inappropriate dosing were the presence of cognitive impairment [adjusted odds ratio (OR*) 1.65, 95% confidence interval (CI) 1.19-2.29, p value (p) = 0.002], weight per kilogram increase (OR* 1.03, 95% CI 1.01-1.04, p < 0.0001), and history of bleeding under apixaban or rivaroxaban (OR* 1.94, 95% CI 1.24-3.03, p = 0.003).

CONCLUSION: This study highlighted the high prevalence of inappropriate apixaban or rivaroxaban doses in older adults, particularly underdosing, which increases the risk of thromboembolism.