Warfarin and flax seed oil interaction and a mechanism for Polyunsaturated Fatty Acid and Warfarin interactions

Warfarin is the most widely prescribed oral anticoagulant in North America and the 11th most prescribed drug in the United States; however, it is underutilized in those who meet criteria for warfarin therapy due to concerns regarding bleeding complications. Warfarin therapy requires frequent monitoring via the International Normalized Ratio (INR) which places considerable time and financial burdens on our healthcare system. In addition, a plethora of genetic, food, drug and herbal interactions are associated with warfarin use. In a recent systematic review of warfarin interactions, 187 separate reports were investigated and only 14 were deemed 'highly probable' for potentiation of warfarin's effect on the INR. One of these 14, fish oil, has recently been touted as a valuable source of omega-3 polyunsaturated fatty acids (PUFAs). Recent data suggest that omega-3 PUFAs like those found in fish oil and flax seed oil (a plant source of omega3 PUFAs) play a protective role cardiovascular disease. Many patients with cardiovascular disease have the potential to receive concomitant warfarin and omega-3s. However, only interactions with warfarin and fish oil have been reported. We present the first such observed ‘possible’ interaction, as assessed by the Drug Interaction Probability Scale (DIPS), and propose a novel mechanism to explain the observed interaction in not only flax seed oil, but fish oil as well.