Warfarin is widely prescribed anticoagulant for the prevention of thromboembolic diseases. However, its use is made difficult by the wide interindividual variation in dose required to achieve a therapeutic effect, the narrow therapeutic range, and the risk of serious bleeding. Warfarin dose requirement is influenced by factors such as intake of vitamin K, ethnicity, age, gender, and genetic factors. Warfarin acts through interference with the recycling of vitamin K in the liver. It has been reported that mutations in VKORC1, CYP2C9, and GGCX cause warfarin resistance.
