Apixaban anti‐Xa levels in clinical practice: A case report

Apixaban is a widely used direct oral anticoagulant that is recommended over warfarin therapy for many clinical indications. In patients with atrial fibrillation, dose reductions are recommended for patients with advanced age (≥80 years), low weight (≤60 kg) or elevated serum creatinine (≥1.5 mg/dL), but there is no routine laboratory monitoring necessary for long term-use. Furthermore, apixaban dose reductions due to renal dysfunction are not recommended when treating acute venous thromboembolism. Apixaban-calibrated anti-Xa assays are readily available at some medical centres, and they may be of clinical utility in certain circumstances such as in patients with renal insufficiency, medication adherence assessment, periprocedural planning, extremes in body weight and advanced age. Here, we describe the case of an elderly patient with chronic kidney disease taking apixaban for acute pulmonary embolism. The patient had an unanticipated prolonged apixaban half-life, with detectable apixaban-calibrated anti-Xa levels for >10 days after the last administered dose, which delayed a necessary surgical intervention by >1 week. This case is an example of appropriately using apixaban-calibrated anti-Xa levels to guide therapeutic decision making in perioperative planning.