A case of bleeding requiring hospitalization that was likely caused by an interaction between warfarin and levamisole

Warfarin is one of the most commonly used oral anticoagulants. Many medications have been shown to influence the prothrombin time in patients treated with warfarin by various mechanisms. We observed a major bleeding episode that resulted from a probable interaction between levamisole (Ergamisol), 5-fluorouracil, and warfarin. It is conceivable that many patients who are predisposed to thromboembolism because of cancer and surgery will be taking this combination of medications.