CRANBERRY/WARFARIN INTERACTION REVISITED

A recent review of case reports regarding an interactionbetween cranberry juice and warfarin failed to show any evidencesupporting the interaction. A few reports in 2002 suggestedthat drinking cranberry juice might result in anincrease in the international normalized ratio (INR) in patientswho were previously stable on warfarin. These reports led theUnited Kingdom Committee on Safety of Medicines to issue awarning that patients taking warfarin should avoid cranberryjuice and cranberry products. When investigators at TuftsUniversity reexamined the data, however, they concludedthat none of the cases demonstrated that loss of INR controlwas caused by cranberry juice. They also performed a studywith cranberry juice and flurbiprofen, which is metabolized bythe same hepatic isoenzyme (CYP2C9). Cranberry juice hadno effect on the metabolism of flurbiprofen. A randomized,double-blind, placebo-controlled trial of the effects of cranberryjuice on the INR in stable warfarin patients is currentlyunder way.

Dr. Garrett is a clinical pharmacistpractitioner at Cornerstone Health Carein High Point, NC.