Tecarfarin

Tecarfarin is a vitamin K analogue which acts by inhibiting vitamin K epoxide reductase. Tecarfarin is highly bound to plasma proteins and has a half life of nearly five days (119 hours). It is not metabolized by cytochrome P450 enzyme system. Instead, the metabolism is by hepatic microsomal carboxylesterases. Hence it has less potential for drug interactions, unlike warfarin. Another advantage is the availability of INR (internationally normalized ratio of prothrombin time) monitoring with a well established therapeutic range. Moreover, unlike other newer antithrombotic agents which do not have antidotes, the action of tecarfarin is reversible by the administration of vitamin K. EmbraceAC compared tecarfarin with warfarin in a randomized double blind trial of those requiring long term anticoagulation: with atrial fibrillation, prosthetic heart valve, venous thromboembolism or a history of myocardial infarction or cardiomyopathy. The primary outcome was control of INR in the form of time in therapeutic range. Six hundred odd patients were enrolled and treated for six months. The time in therapeutic INR range was 74 percent for tecarfarin and 73.2 percent for warfarin (P = 0.506). Authors attribute the surprisingly high time in therapeutic range for warfarin in this trial to be due to the skill of physicians at the dose control center.