In a recent update of the Coumadin (Warfarin) prescribing information and the corresponding Medication Guide1, the caution statement to avoid cranberry juice or cranberry products while patients are taking warfarin has been removed. 

The Medication Guide was updated because, while several case reports 2-3 reported a potential interaction between cranberry products and warfarin, more recent clinical trials that studied patients before and after consuming cranberry juice found no clinically significant interaction.Two of the most recent studies have found similar results showing that consumption of 8-16 ounces of cranberry juice daily for up to 1-2 weeks was safe.4-5 Neither study evaluated any cranberry products other than cranberry juice; however, the revised labeling 1 has removed caution against cranberry juice and other cranberry products allowing warfarin patients to also consume alternate cranberry products.

The effect of large amounts of cranberry products (~0.5-2 liters of juice, or 30-120g of sauce, or 1,00mg capsules per day) for long periods of time on warfarin variability still remains to be elucidated. Thus thorough patient education is key in order to facilitate the safe use of cranberry products in patients on warfarin. Highlighting the importance of type, appropriate amount, and duration of cranberry product consumption is especially important until further data becomes available on consumption of larger product amounts for longer time durations. See below for a Patient's Guide to Cranberry Products and Coumadin (Warfarin) that you might find helpful in education of your patients.

1. Bristol-Myers Squibb Company. Medication Guide for Coumadin Tablets and Coumadin for Injection [Package Insert]. Princeton, NJ: Bristol-Myers Squibb Company. 2011
2. Rindone JP, Murphy TW. Warfarin-cranberry juice interaction resulting in profound hypoprothrombinaemia and bleeding. American Journal of Therapeutics 2006; 13: 283-284.
3. Paeng CH, Sprague M, Jackevicius CA. Interaction between warfarin and cranberry juice. Clinical Therapeutics. 2007; 29(8):1730
4. Ansell, Jack. (2009). The absence of an interaction between warfarin and cranberry juice: a randomized, double-blind trial. Journal of Clinical Pharmacology, 49:824-830.
5. Mellen, Chadwick K. (2010). Effect of high-dose cranberry juice on the pharmacodynamics of warfarin in patients. British Journal of Clinical Pharmacology, DOI:10.1111/j.1365-2125.2010.03674.
6. Bristol-Myers Squibb Company. Medication Guide for Coumadin Tablets and Coumadin for Injection [Package Insert]. Princeton, NJ: Bristol-Myers Squibb Company. 2009

A Patient's Guide to Cranberry Products and Coumadin (Warfarin)

Coumadin (Warfarin) is a commonly prescribed "blood thinner." Its therapeutic effect varies in any given individual, and even minor variations can lead to problems. Therefore, your healthcare providers may advise against taking certain foods and herbal supplements. Are cranberry products safe to consume while also taking warfarin?

Clinical trials that evaluated the effects of cranberry consumption on warfarin therapy have not found a clinically significant interaction. According to these data, consumption of cranberry products appears to be safe in patients taking warfarin. The Coumadin (Warfarin) prescribing information and medication guide were recently updated, and no longer list cranberries as a potentially interacting food.  

Recommendations

• Moderate intake of cranberries such as drinking cranberry juice, about 1 -2 glasses per day is safe in patients taking warfarin.
• The effect of drinking or eating extremely large amounts of cranberry products (~0.5-2 liters of juice, or 30-120g of sauce, or 1,00mg capsules per day) for long periods of time on warfarin variability requires further investigation.
• Talk to your healthcare provider before large increases in cranberry products in your diet for extended periods of time.
• Check your skin closely for easy bruising or red spots. This may be a sign of bleeding. If you notice any bleeding, notify your doctor right away.