venous and arterial thromboembolism because of oral intake and its low price. However, it has a narrow therapeutic range, a high rate of bleeding complications, and highly variable dose adjustment between individuals. Dose adjustment is associated with age, gender, weight, height, body surface area, and CYP2C9 and VKORC1 genetic polymorphisms. We report a patient with heterozygous VKORC1 gene mutation who failed to reach a therapeutic level of international normalized ratio (INR) with warfarin therapy.

Keywords: varfarin direnci, VKORC1 gen polimorfizmi.