Use of Apixaban in Atrial Fibrillation With Ritonavir-Boosted Antiretroviral Therapy: A Case Report

Purpose Direct oral anticoagulants (DOACs) pose a challenge when given with potent CYP3A4 and P-gp inhibitors, such as the commonly prescribed pharmacokinetic booster ritonavir. As per the manufacturer, apixaban offers a dose reduction when administered concurrently with ritonavir; thus, we explore the clinical indication and safety of apixaban when given with ritonavir-boosted highly active antiretroviral therapy (HAART) in an HIV patient. We describe a 73-year-old male with extensive cardiac history, including a past medical history of resolved left ventricular thrombus, newly diagnosed non-valvular atrial fibrillation treated with warfarin, and HIV infection treated with ritonavir-boosted HAART. The patient presented to the emergency department with bleeding from multiple sites, necessitating the use of vitamin K. Consequently, his hospital course was complicated by episodes of minor bleeding and labile INR. Due to the complicated nature of his condition and the potential for drug-drug interactions (DDIs), he was transitioned from warfarin to apixaban. Since there is little readily available data to support the use of rivaroxaban and dabigatran with ritonavir, our patient was safely started on dose-reduced apixaban for stroke prophylaxis in atrial fibrillation due to the predictable nature of apixaban pharmacokinetics and proven superiority regarding adverse effects, as compared to other DOACs. Conclusion Dose-reduced apixaban is a safe and viable choice in patients with atrial fibrillation warranting stroke prophylaxis while concurrently receiving ritonavir-boosted HAART.