Pharmacy Services

Cranberry - Warfarin (Coumadin) Interaction

December 20, 2012

A recent update to warfarin (Coumadin) prescribing information removed the drug interaction between warfarin and cranberry products. This drug-interaction warning was originally supported by several case reports, but evidence from more recent clinical did not demonstrate an interaction. These studies evaluated patients consuming 8-16 ounces of cranberry juice daily for up to 1-2 weeks, and revealed no safety concerns with concomitant warfarin therapy.

Despite these studies only evaluating the interaction of warfarin and cranberry juice, the interaction between warfarin and cranberry products such as the cranberry sauce or capsules has also been removed from prescribing information. The interaction between warfarin and larger amounts of cranberry juice or cranberry products was not fully evaluated during clinical studies. In addition, consumption of cranberry juice and products for long periods has not been evaluated in patients taking warfarin. As a result, it is important to educate patients on the safe type, quantity, and duration of cranberry consumption with warfarin therapy.

Recommendations for educating patients about warfarin and cranberry consumption include:

  • Drinking 1-2 glasses of cranberry juice daily is safe in patients taking warfarin.
  • Consuming larger amounts of cranberry products or for a longer duration has not been fully evaluated.
  • Consult a healthcare professional before making significant changes in cranberry consumption.
  • Continuously monitor for signs of bleeding while taking warfarin.

December 20, 2012; University of Utah, Drug Information Service. Copyright 2012, Drug Information Service, University of Utah, Salt Lake City, UT.