SUMMARY:  

Warfarin is an anticoagulant that is also known by the brand name Coumadin. It is used in the treatment of myocardial infarction and thromboembolic complications. There is a wide variety of tablet strengths from 1 mg to as high as 10 mg. When dosing warfarin it is very patient-specific. The therapeutic goal is based on various factors and treatment nomograms may vary from institution to institution. Prior to initiation it is wise to establish the patient’s genetic variant for CYP2C9 since this will play a large role in predicting their drug sensitivity. When attempting to reach a therapeutic target the healthcare professional uses INR readings to determine the level of anticoagulation. Generally a range between 2-3 is common with 2.5-3.5 when a high level of intensity is required. Other factors that may help determine patient response are age, race, and diet. The mechanism of action for warfarin lies in the antagonism of Vitamin K which leads toward the inhibition of coagulation factors 2, 7, 9, and 10. The rate-limiting factor can be seen as factor 2 due to it’s long half-life of 60-72 hours. Although INR elevation can be seen in 24-48 hours, therapeutic benefits are not achieved until around 5-7 days after initiation. There is a black box warning for bleeding risk so a patient’s INR should be monitored regularly.