Adverse interaction between capecitabine and warfarin resulting in altered coagulation parameters and bleeding: case report and review of the literature

Capecitabine can interact with warfarin, resulting in altered coagulation parameters and bleeding. Four cases have been reported. We describe a fifth case with life-threatening interaction between these two drugs. A 67-year-old female with metastatic breast cancer developed hemorrhagic blisters, purpura and ecchymoses. She had been well controlled on long-term warfarin (5 mg/day). Capecitabine was initiated 4.5 weeks prior to the bleeding episode. Laboratory work-up revealed an international normalized ratio of 8.56, partial prothrombin time of 61 seconds and prothrombin time of 5.2%. The coagulation parameters gradually normalized within 4 days following vitamin K administration and discontinuation of capecitabine and warfarin. Careful monitoring of coagulation parameters and proper adjustment of the warfarin dose are required in patients taking warfarin and capecitabine concomitantly.