Very High Warfarin Dosing Requirements in a Patient With Tuberculosis and a Pulmonary Embolism: A Case Report.

Purpose: To describe a case of significantly increased warfarin requirements in a patient receiving rifampin for the management of tuberculosis. Summary: A 76-year-old male was admitted due to altered mentation, cough, and weight loss. He was diagnosed concurrently with tuberculosis and a pulmonary embolism. Given the profound effect of rifampin on CYP450 enzymes, direct oral anticoagulants were avoided and warfarin therapy was selected. Management was further complicated by a gastrointestinal bleed during admission, history of cancer, and low body weight. After several weeks of daily international normalized ratio monitoring, a stable regimen of 14 mg of warfarin daily was established, allowing for the patient's safe discharge. Practice Implications: This report underscores the significance of tailored treatment plans, vigilant monitoring, and interdisciplinary collaboration which are necessary to navigate the complexities associated with these medications and optimize patient outcomes.