Modest intake of cranberry juice OK with warfarin
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Patients on warfarin advised to drink cranberry juice in moderation |
The significance of an interaction between cranberry juice and warfarin has been called into question by the authors of a recent study (Journal
of the American Dietetic Association 2006;106:2057).
Researchers randomised seven men stabilised on warfarin to receive
one week of cranberry juice (250ml per day) followed, after one week’s
washout, by a week of placebo drink, or vice versa. They found no significant
changes in international normalised ratio (INR) for either group for
all test points in the study.
The authors say that, despite the small sample size, it is clear that
a cranberry juice interaction is not a general effect in every patient
taking anticoagulants.
However, the authors say: “The study does not eliminate the possibility
of idiosyncratic susceptibility to the effects of cranberry juice on
warfarin metabolism in individuals with genetic polymorphisms of the
cytochrome P450 system.”
They suggest that modest consumption of cranberry products and routine
INR monitoring be emphasised to patients.
The Medicines and Healthcare products Regulatory Agency’s most
recent advice (October 2004) states: “It is not possible to define
a safe quantity or brand of cranberry juice and therefore patients taking
warfarin should avoid this drink unless the health benefits are considered
to outweigh any risks.” The MHRA says that it is not known whether
other cranberry products, such as capsules or concentrates, might interact
with warfarin and recommends similar caution with these products. |
The
Pharmaceutical Journal
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