Potential interaction between pomegranate juice and warfarin

To my knowledge, no published reports have described an interaction between pomegranate juice and warfarin. Investigators from previous animal and in vitro studies have reported a potential for pomegranate juice to inhibit metabolism involving the cytochrome P450 system, an effect that could translate into a clinical drug-diet interaction with warfarin. This case report describes a 64-year-old Caucasian woman who was treated with warfarin for recurrent deep vein thrombosis. She had been receiving a relatively stable dosage of warfarin 4 mg/day for several months, with stable international normalized ratios (INRs). During that time, the patient was consuming pomegranate juice 2-3 times/week. She stopped drinking the juice, and her INRs became subtherapeutic. Her dosage of warfarin was increased to maintain therapeutic anticoagulation. No rechallenge with pomegranate juice was performed. Use of the Drug Interaction Probability Scale indicated a possible relationship between the patient's subtherapeutic INR and the pomegranate juice. Although this potential interaction needs to be explored further, clinicians should be aware of the interaction and thoroughly interview and closely monitor their patients who are receiving warfarin.