Ranitidine-Warfarin Interaction

Excerpt

To the Editor: We report a possible prolongation of prothrombin time (PT) of warfarin by ranitidine. A 65-year-old woman with a past medical history of a cerebral vascular accident and an aortic valve replacement was discharged from the hospital with a diagnosis of recurrent deep-vein thrombosis, recurrent gastrointestinal bleeding, and iron-deficiency anemia. Four days before discharge, the ranitidine dose was increased to 600 mg daily because on the recommended 300-mg daily maintenance dose for several months the patient developed recurrent gastrointestinal bleeding. At discharge, her medications (all taken orally) included warfarin, 5 mg once daily; ranitidine, 300 mg twice daily;