Dabigatran: An Alternative to Warfarin After Over Half a Century

Abstract

For over half a century, warfarin or other vitamin K antagonists (VKA) (such as acenocoumarol, available in Greece and other countries), have been the gold standard and the only oral anticoagulants available which have been shown to effectively treat thromboembolism. However, their use has been plagued by inherent limitations with cumbersome monitoring via laboratory-guided adjustments of the dose, narrow therapeutic window, a lot of drug and food interactions and unpredictable and variable response.  This has hindered patient compliance and has led to suboptimal therapy and poor anticoagulation control. Also patients unable or unwilling to take VKA have been offered no other choice of equivalent efficacy, i.e. until recently. Reasons for not receiving a VKA may comprise the following: drug allergy, patient refusal to take or decision to discontinue the drug, inability to maintain the international normalized ratio (INR) in the 2.0-3.0 range, physician decision as to the inappropriateness of receiving the drug, and/or inability to monitor the INR (lack of or difficulty in accessing a laboratory or lack of family support or assistance with this tedious task).

These hurdles of conventional anticoagulant therapy have spawned efforts to develop new medications that will surpass these drawbacks while matching the efficacy of VKAs. Factor Xa has a strategic role in the coagulation cascade, critically poised at the juncture of the contact activation (intrinsic) and the tissue factor (extrinsic) coagulation pathways proximal to thrombin, both activating the final common pathway and leading to fibrin formation. Active factor Xa hydrolyzes and activates prothrombin to thrombin. Thrombin is the most important constituent of the coagulation cascade and has a broad array of functions with a primary role in the conversion of fibrinogen to fibrin, the building structure of a hemostatic plug... (excerpt)