Warfarin Institute of America
DEDICATED TO YOUR HEALTH SINCE 2000
THAT'S A GOOD QUESTION
The question about warfarin and cranberry juice keeps coming up. I have decided to have it answered again.
Cranberry juice and warfarin is listed as a major drug interaction on the pharmaceutical references Micromedex and Facts and Comparisons.1,2 The cited literature contains only a few case reports of nonspecific increases in INRs and one of an elderly man whom developed fatal gastrointestinal and pericardial hemorrhages after drinking an unknown quantity of cranberry juice.1,2 In the patient information guide by Bristol-Myers Squibb, the makers of Coumadin, they recommend avoiding drinking cranberry juice or eating cranberry products.3 The mechanism for the proposed interaction is not known. Cranberry is not known to contain coumarins, affect the Cytochrome P450 isoenzyme system, have antiplatelet affects, contain salicilates, or any other potential mechanisms by which a drug interaction could occur.4 At this time it is not definitively known whether or not an interaction between warfarin and cranberry exists. My feeling would be that if that a person were to drink cranberry juice they should limit intake to a small glass per day. If the patient wanted to use an over the counter cranberry supplement, I would recommend not using it because content can very widely in supplements. The interaction between cranberry and warfarin will probably never be definitive and is more than likely just speculation.
References:
1. Micromedex
2. Facts and comparisons
3. Coumadin, patient information
4. Coumadin package insert
©2007 Matthew Thielbar Used by permission.
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Last updated January 22, 2007
