ClotCare: Blood Clots, Stroke, Heart Attack
Wednesday, May 22, 2024
Home   |   DVT/PE   |   Blood Clots   |   Coumadin/Warfarin   |   New Patients   |   Self Testing   |   Email List   |   Donate

Pick a Topic:

Find info on a:

We subscribe to the HONcode principles of the HON Foundation. Click to verify.
ClotCare complies with the HONcode standard for trustworthy health
verify here.

ClotCare is a member of the Coalition to Prevent Deep Vein Thrombosis (DVT Coalition)  ClotCare is a member organization of the Coalition to Prevent Deep Vein Thrombosis. Click here to learn more about the Coalition to Prevent Deep Vein Thrombosis and DVT Awareness Month, which is held each March.

Warfarin - Cranberry Juice Interaction: Expert Finds Data Lacking

Henry I. Bussey, Pharm.D.
June, 2006

David J. Greenblatt, M.D. (Chair, Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine) recently reviewed the available data which generated a lot of concern that ingestion of cranberry juice might significantly alter the INR in patients taking warfarin. The data are from case reports in the United Kingdom and led the UK Committee on Safety of Medicines to issue a warning that patients taking warfarin should avoid cranberry juice or cranberry products. Dr. Greenblatt's group examined each case report and found "not a single one of these cases plausibly demonstrated that loss of anticoagulant control was caused by cranberry juice." Further, his group performed a study with cranberry juice and flurbiprofen (which is metabolized by the same enzyme that plays a major role in warfarin metabolism, the hepatic CYP2C9 enzyme) and found no effect of cranberry juice on the metabolism of this medication. His group is now conducting a randomized, double-blind, placebo-controlled trial of the effect of cranberry juice on the INR in stable warfarin patients. More data should be forthcoming soon, but Dr. Greenblatt concludes that current evidence does not support a need for concern regarding a warfarin v. cranberry interaction.

Editor's note: Of course, it is possible that cranberry juice might interact with warfarin through some other mechanism; and/or one could postulate that the interaction might be evident only in persons with certain types of 2C9 polymorphisms (who may or may not be included in a randomized controlled trial). But looking for an alternative mechanism for such an interaction or examining the potential that an interaction may occur only in those patients with certain genetic polymorphisms hardly seems justified without more clinical data to suggest that an interaction actually exists. (HIB)


Greenblatt DJ. Cranberry Juice & warfarin: Is there an interaction? Anticoagulation Forum Newsletter 2006; 10(1):1, 3.

Ask a question about blood clots or anticoagulant medications Have questions? Ask ClotCare. Send questions by email to

ClotCare is a 501(c)(3) non-profit organization generously supported by your tax-deductible donations and grants from our industry supporters.

Blood Clot Activities Calendar

New Postings:

Click here to view full list of new postings
ClotCare Home | New Postings | Patient Postings | Clinician Postings | Join Our Email List | Useful Web Links
CE Opportunities | Training Programs | DVT & PE Stories | Editorial Board | Financial Support
About ClotCare | DVT Coalition | Donate to ClotCare | Contact Us
Key topics discussed on ClotCare include: Blood Clots | Deep Vein Thrombosis (DVT) | Pulmonary Embolism (PE) | Atrial Fibrillation (A. Fib or AF) | Heart Attack | Stroke | Transient Ischemic Attack (TIA) | Mini Stroke | Bleeding Complications | Vascular Surgery | Surgical Blood Clot Removal | Warfarin | Coumadin | Lovenox | Low Molecular Weight Heparin (LMWH) | Heparin | Anticoagulants | Plavix | Aspirin | Antiplatelets | Blood Thinners
Copyright 2000-2018 by ClotCare. All rights reserved.
Terms, Conditions, & Privacy | Image Copyright Information
19260 Stone Oak Parkway, Suite 101 | San Antonio, TX 78258 | 210-860-0487
Send comments to
Wednesday, May 22, 2024