Category: Professional Posters
Purpose: Apixaban is a direct oral anticoagulant (DOAC) used for both venous thromboembolism (VTE) prophylaxis and treatment as well as for stroke prevention in non-valvular atrial fibrillation. Dosing of apixaban varies based on indication, concomitant medications, and patient factors such as age, weight and serum creatinine. Inappropriate low doses of apixaban may put patients at increased risk of events such as stroke, deep vein thrombosis or pulmonary embolism. This medication use evaluation was designed to assess for the rate of inappropriate low-dose apixaban and associated patient factors.
Methods: All patients that received at least one dose of 2.5 mg apixaban from the period of 5/1/18 to 4/30/19 were included in the study. Each use was assessed for indication, grouped into treatment of atrial fibrillation or VTE treatment/prophylaxis. Appropriateness of dosing was based on product labeling. Patient demographic data including sex, age and weight were included for data analysis. Linear regression analysis compared the rate of inappropriateness based on indication with further subgroup ANOVA analysis to assess for patient factors associated with inappropriate low dosing.
Results: Out of 299 patients, 66 (22%) met criteria for inappropriate low dose. Patients receiving apixaban with an indication for atrial fibrillation (n=118) were dosed inappropriately 46.6% (95% CI 37.6% to 55.6%) compared to patients receiving apixaban for VTE prophylaxis or treatment (n=179) who were dosed inappropriately 5.8% (95% CI 2.4% to 9.0%) of the time (p<0.001). Subgroup ANOVA analysis found significantly higher rates of inappropriate dosing for VTE prophylaxis/treatment patients based female sex (p=0.001) and higher weight (p=0.045) but not for age (p=0.536). Similar analysis performed for atrial fibrillation patients found significantly higher rates of inappropriate dosing for atrial fibrillation patients based on older age (p=0.012), lower weight (p<0.001) but not for sex (p=0.920).
Conclusion: The use of inappropriate low doses of apixaban at an academic medical center occurs at high rate, particularly in patients receiving anticoagulation for atrial fibrillation. Furthermore, patient factors such as age, weight and sex may predispose patients to receive inappropriate low doses of apixaban. Better education of providers and expansion of warning prompts during ordering may help mitigate this issue. Further expansion of the collected data to include event rates for thrombotic and bleeding events will provide a better understanding of the safety issues arising from inappropriate low dose apixaban.