Interaction potential between cranberry juice and warfarin.
OBJECTIVE
The interaction potential between warfarin and cranberry juice is discussed.


CONCLUSIONS
Reports from the United Kingdom have raised concern over the interaction potential between cranberry juice and warfarin. Warfarin is the most commonly prescribed oral medication for anticoagulation therapy. Cranberry juice is a flavonoid, which has been shown to induce, inhibit, or act as a substrate for the biosynthesis of several cytochrome P-450 (CYP) isoenzymes. Specifically, cranberry juice may inhibit the activity of CYP2C9, the primary isoenzyme involved in the metabolism of S-warfarin. A search of the medical literature identified three peer-reviewed case reports and two peer-reviewed, prospective, randomized, placebo-controlled clinical trials using metabolic surrogates of warfarin (flurbiprofen and cyclosporine) that described possible interactions between cranberry juice and warfarin. Two case reports suggested that cranberry juice increased the International Normalized Ratio (INR) of patients taking warfarin, but neither clearly identified cranberry juice as the sole cause of INR elevation. One case report appeared to show a correlation between the effects of cranberry juice and warfarin metabolism. Both clinical trials indicated the lack of an interaction between cranberry juice and CYP isoenzymes 2C9 and 3A, both of which are necessary in warfarin metabolism. More studies are required to determine the potential interaction between cranberry juice and warfarin.


CONCLUSIONS
The available data do not seem to show a clinically relevant interaction between cranberry juice and warfarin; however, patients taking warfarin with cranberry juice should be cautioned about the potential interaction and monitored closely for INR changes and signs and symptoms of bleeding.
Pham
David Q
DQ
Arnold & Marie Schwartz College of Pharmacy and Health Sciences, Long Island University, 75 DeKalb Avenue, Brooklyn, NY 11201, USA. david.pham@liu.edu
Pham
Antony Q
AQ
D000925:Anticoagulants / Q000009:adverse effects*; D001189:Aryl Hydrocarbon Hydroxylases; D001628:Beverages; D002986:Clinical Trials as Topic; D065729:Cytochrome P-450 CYP2C9; D016903:Drug Monitoring; D005260:Female; D005419:Flavonoids; D018565:Food-Drug Interactions; D006470:Hemorrhage / Q000139:chemically induced; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D029799:Vaccinium macrocarpon; D014813:Vitamin K Deficiency; D014859:Warfarin / Q000009:adverse effects* / Q000493:pharmacokinetics*
D000925:Anticoagulants; D005419:Flavonoids; D014859:Warfarin; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases