Warfarin and cranberry juice: an interaction?

Herein, the case is reported of a persistently elevated INR consequent to an interaction between warfarin and cranberry juice in a patient with a prosthetic mitral valve. The elevation in INR was noted two weeks after the patient began to drink cranberry juice. Subsequent symptoms included postoperative bleeding problems. The bleeding was thought due to a biologically plausible interaction between the drug and the juice. It was concluded that patients taking warfarin should limit their cranberry juice intake.