Warfarin and Cranberry Juice: Time to Lose the Warnings?

Expert Interview With Jack E. Ansell, MD

Linda Brookes, MSc


September 02, 2010

In This Article

Summary Points

The warning that there is a potential to enhance the effect of warfarin prolonging the INR with cranberry juice intake is mostly based on faulty reports, many of which are not even case reports but case comments consisting of a few sentences about a possible interaction. On the basis of anecdotal reports, the current study, and other randomized and surrogate trials, there should be no problem with patients taking warfarin drinking average or moderate amounts of cranberry juice.

The history of the cranberry juice-warfarin interaction seems to follow a pattern set by other purported interactions with warfarin, including some with antibiotics, in which a temporal relationship appears to exist between the suspected precipitant drug and a change in patient response to warfarin. The cases often lack sufficient detail or include confounders that make it impossible to establish causation. When prospective, controlled studies are done, the interaction is not observed.

Physicians should advise patients to have a consistent diet from week to week and not go on diet binges or change their diet dramatically for any period of time. The physicians can then adjust the warfarin dose to accommodate their diet.

New anticoagulants, such as rivaroxaban, apixaban, or dabigatran, appear to have few, if any, drug interactions and no significant dietary interactions, and their anticoagulant effect is predictable, so they do not, in a general sense, require routine monitoring. As a substitute or an alternative to warfarin, these drugs will make life much each easier for the physician, as well as for the patient. On the other hand, they will not replace warfarin entirely; not everybody is immediately going to switch to one of these new agents.


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