Dose-Reduced Apixaban for Thromboembolism in a Patient With Obesity on Cobicistat: A Case Report

Background/Objective: Current guidelines recommend a 50% dose reduction of apixaban for patients receiving strong CYP3A4/P-glycoprotein (P-gp) inhibitors regardless of body habitus. However, evidence supporting this dose adjustment in patients with severe obesity (BMI >40 kg/m²) is limited. This report describes the use of dose-reduced apixaban for the treatment of venous thromboembolism in a patient with a BMI >50 kg/m² receiving a strong CYP3A4/P-gp inhibitor. Summary: A 38-year-old female with a BMI of 81.71 kg/m² and a history of HIV on a cobicistat-containing antiretroviral regimen was diagnosed with a left femoral deep vein thromboembolism. She was initially treated with warfarin and enoxaparin bridge therapy but was transitioned to apixaban prior to discharge. Apixaban was initiated at a 50% dose reduction due to the concomitant use of cobicistat, a strong CYP3A4/P-gp inhibitor. The patient successfully completed therapy without recurrence of thromboembolism or bleeding complications. Conclusion: This case demonstrates the successful use of dose-reduced apixaban in a patient with a BMI >50 kg/m² receiving a CYP3A4/P-gp inhibitor for the treatment of venous thromboembolism and adds to available literature on apixaban dosing in patients with obesity.