The number of warfarin prescriptions jumped 45 percent to nearly 31 million in 2004, according to the Food and Drug Administration. Although this blood-thinning drug has been widely used around the world to prevent blood clots, it's among the top 10 drugs with the most serious adverse reactions. Cranberry juice is one of the foods long thought to interact with warfarin and cause excess bleeding, but researchers are finding that cranberry might not be as harmful as once thought.
Identification
Vitamin K, found in various vegetables and fruits, is used by your body to form blood clots and prevent bleeding from skin wounds and internal injuries. However, people with genetic disorders, women on birth control pills and other high-risk groups may clot too easily and experience life-threatening clotting in the heart, lungs and brain. Warfarin is sold under the brand names Coumadin and Jantoven and decreases your body's ability to form blood clots by inhibiting vitamin K's clotting factors. But eating certain types of foods can affect warfarin's ability to do its job. A prothrombin time blood test is used to measure blood clotting time, with an International Normalized Ratio given as well. Your PT and INR numbers reveal how quickly or slowly your blood clots.
Potential Cranberry Dangers
It's been thought that cranberry juice interacted with certain enzymes critical for your body to clear itself of chemicals such as medications like warfarin. Although there have been reports of individual patients having their PT and INR levels affected by cranberry juice, they are usually isolated cases involving unusually high amounts of cranberry juice, such as one case published in the "Journal of the Royal Society for the Promotion of Health" of an elderly man who had a fatal internal hemorrhage after consuming only cranberry juice for two weeks while maintaining his usual dosage of warfarin.
No Cranberry Effects
A review of several clinical trials, published in the May 2010 issue of the "American Journal of Medicine," concluded there was no evidence to support the interaction between cranberry juice and warfarin and that initial precautionary warnings were limited to anecdotal case reports and represent misleading conclusions. A study published later that year in the "Journal of Experimental Pharmacology" observed that the lack of effects of cranberry juice upon PT/INR levels was likely due to the fact the juice is chemically transformed and diluted before entering the liver, where warfarin is metabolized.
Considerations
Although the research seems to be leaning toward the recommendation that cranberry juice is generally safe if you're taking warfarin, avoid consuming large amounts of the juice. Check with your doctor before adding cranberry juice to your diet, especially if you have difficulties keeping your PT/INR between the generally recommended therapeutic range of 2.0 to 3.0.
References
- "Circulation"; A Patient's Guide to Taking Coumadin/Warfarin; Karen Fiumara, PharmD, and Samuel Z. Goldhaber, M.D.; 2009
- "Archives of Internal Medicine"; Bleeding Complications with Warfarin Use: a Prevalent Adverse Effect Resulting in Regulatory Action; D.K. Wysowski, et al.; July 2007
- "American Journal of Medicine"; Cranberry Juice and Warfarin: When Bad Publicity Trumps Science; Z. Zikria, et al.; May 2010
- "The Journal of the Royal Society for the Promotion of Health"; Fatal Haemopericardium and Gastrointestinal Haemorrhage Due to Possible Interaction of Cranberry Juice with Warfarin; A.P. Griffiths; November 2008
- "Journal of Experimental Pharmacology"; The Warfarin--Cranberry Juice Interaction Revisited: A Systematic in Vitro--in Vivo Evaluation; Ngoc Ngo, et al.; September 2010
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