Warfarin: Looking Beyond Vitamin K in Diet

Warfarin has been widely used for its anticoagulant properties. It has a narrow therapeutic range with complex interactions with various dietary products, herbal supplements, and with other medications. We recently encountered a case of warfarin coagulopathy in a patient that had been on stable doses of warfarin since 2011 with successful maintenance of international normalized ratio in the therapeutic range. By the process of elimination, the cause was attributed to the patient’s recent inclusion of pineapple papaya smoothies in her diet. This study highlights the importance of detailed history taking with a focus on diet changes and supplements in patients on warfarin. Warfarin has an extensive list of interactions with prescription and over-the-counter medications, various vegetables, fruits, and herbal supplements through an effect on warfarin metabolism by cytochrome 450 enzymes. While it is a well-known fact that green leafy vegetables diminish warfarin therapeutics due to their high Vitamin K content, warfarin interactions with fruits are less well known. The focus of this article is a review of the literature about the plausible interactions of pineapple and papaya with warfarin. We have briefly touched on the interactions of warfarin with other fruits.