Doctors prescribe Coumadin, the brand name for the medication warfarin, to help prevent the formation of blood clots. For example, if you have had a heart valve implant or a heart attack, you might take Coumadin to help manage your condition. However, some foods and medications may interfere with the action of Coumadin and decrease its effectiveness. Evidence on the effect of cranberries and cranberry juice in people who take Coumadin is not totally clear.
Benefits of Cranberry Juice
Cranberries and cranberry juice have been used to treat both kidney and bladder conditions for many years, according to the University of Maryland Medical Center. Drinking cranberry juice may prevent urinary tract infections, lower the risk of developing stomach ulcers and lower LDL cholesterol. Although large studies have not verified these health benefits, your physician may recommend that you drink cranberry juice each day. However, if you take Coumadin, large amounts of cranberry juice may affect your medication.
Concerns about Cranberry and Coumadin
Cranberry juice may decrease the activity of cytochrome P450-2C9, which is the enzyme that metabolizes Coumadin in the body.If the enzyme does not get rid of the Coumadin, you may end up with extra medication in your body, according to an article in the spring 2006 issue of "AntiCogulation Forum." Extra Coumadin may increase the anticoagulant activity and cause your blood to be even less likely to clot. Different case reports and small studies have supported this suggestion; for example, a study in the May-June 2006 issue of the "American Journal of Therapeutics" found that the clotting ability of a man on Coumadin decreased once he began drinking daily cranberry juice. After several of these reports, regulatory agencies including the Food and Drug Administration and the U.K. Committee on Safety of Medicines issued warnings about possible interactions of cranberry juice and Coumadin, according to the Thrombophilia Awareness Project.
Opposing Data
More-recent studies have called these concerns into question. According to an article in the August 2007 issue of "Clinical Therapeutics," a patient on Coumadin who drank large amounts of cranberry juice did have some changes in his blood-clotting test results but did not experience any excess bleeding. A controlled study published in the July 2009 issue of the "Journal of Clinical Pharmacology" found that cranberry juice did not have any effect on the levels of Coumadin in the blood.
What Should You Do?
Since the evidence showing an interaction between cranberry juice and Coumadin varies, you may wonder what to do if you take this medication. Although recent data suggest it may be safe to drink cranberry juice while on warfarin, you should discuss this with your physician. As of 2011, the warnings from the regulatory agencies are still in place. Your physician will closely monitor your blood work and determine if you are having excessive bleeding if you are using cranberry juice while in Coumadin, suggests by David Q. Pham and Antony Q. Pham in a 2007 issue of "American Journal of Health-System Pharmacy."
References
- Thrombophilia Awareness Project: Cranberry juice, Grapefruit juice and warfarin (Coumadin®)
- Journal of Clinical Pharmacology; "The Absence of an Interaction Between Warfarin and Cranberry Juice: a Randomized, Double-Blind Trial"; Ansell and colleagues; 2009.
- American Journal of Therapeutics; Warfarin-Cranberry Juice Interaction Resulting in Profound Hypoprothrombinemia and Bleeding"; Rindone and colleagues; 2006.
- Clinical Therapeutics; "Interaction Between Warfarin and Cranberry Juice"; Paeng and colleagues; 2007.
- PubMed Health: Warfarin
- American Journal of Health-System Pharmacy; "Interaction Potential Between Cranberry Juice and Warfarin"; David Q. Pham and Antony Q. Pham; 2007.
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