Bleeding DisordersCAM InteractionsCranberry

The final word on the warfarin-cranberry interaction?

“The warning that there is a potential to enhance the effect of warfarin… with cranberry juice intake is mostly based on faulty reports.”

That’s the conclusion by researchers at Lenox Hill Hospital, in New York City.

First, the details.

  • A search of the medical literature revealed 15 case reports, including the initial unpublished brief reports to the Committee on Safety of Medicines and 6 published case reports.
  • 7 clinical studies were also analyzed, including 3 using warfarin and 4 that used surrogate drugs.

And, the results.

  • Only 2 case reports used a validation scale suggesting a “probable” interaction, but even in these patients there were many reasons to question the validity of a relevant drug interaction.
  • Clinical studies and surrogate markers found no evidence to support the interaction between cranberry juice and warfarin.

The bottom line?

The initial precautionary warnings about the warfarin-cranberry interaction are based on anecdotal case reports and are misleading.

When one considers the usual amount of cranberry juice that people drink, moderate consumption of cranberry juice does not affect anticoagulation [clotting]. The authors would like a re-examination of initial warnings based on scientific evidence.

Examples of conflicting studies are here and here.

And the latest case report of a warfarin-cranberry interaction can be found here.

9/08/10 21:37 JR; updated

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.