Cranberry & Warfarin - A lack of interaction

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PTINR.com Staff

If you are taking Coumadin®, "To drink or not to drink cranberry juice" may remain a question for you. A recent, well designed clinical study has found that 8 ounces of cranberry juice per day is safe for patients taking Coumadin®.¹

Controversy has circled cranberry juice because five, single case reports since 2003 of possible elevations in INR test results by patients consuming cranberry juice. Each of these cases however included poorly nourished patients taking antibiotics – which is known to increase INR test results.

The study population was small (30 patients), but sufficient to determine if cranberry juice represented a potential interaction with Coumadin®. Patients were tested weekly to evaluate potential interactions.

The study, led by Jack Ansell, MD was overseen by the Boston Medical Center, Tufts University School of Medicine and Lennox Hill Hospital and evaluated patients on and off cranberry for 2 weeks. The work was supported by the Ocean Spray company and the Department of Health and Human Services1 and published in 2009 Journal of Pharmacology.

The authors noted that “reasonable” quantities of cranberry included 8 ounces of cranberry juice and could not speculate on effects of larger amounts consumed. Your results may vary. You may want to discuss this with your healthcare team. Home INR testing is a valuable tool of evaluating the affects of products like cranberry and other dietary choices and will alert you of increasing or decreasing INR test results sooner than patients who test less often.