Recent developments in antithrombotic therapy: will sodium warfarin be a drug of the past?

Warfarin and heparin have formed the mainstay in the prophylaxis of deep vein thrombosis (DVT), stroke prevention in atrial fibrillation, and treatment of thromboembolic disease (TED). However, these choices are hampered by difficult administration, interactions with other medications, side effect profile, and limited indications for treatment. Anti-factor Xa (anti-Xa) inhibitors have already entered the drug market with the drug Fondaparinux being the first anti-Xa inhibitor to be approved for use in the U.S. by the Food and Drug Administration (FDA), and other drugs such as idraparinux being currently in development. A new class of medications, known as direct thrombin inhibitors (DTI), includes the parental agents lepirudin, argatroban and bivalirudin which have been approved by the FDA and the oral agents ximelagatran, melagatran and dabigatran. The latter three drugs which are oral DTIs may soon replace warfarin and heparin as the preferred medications for DVT prophylaxis and for reducing the relative risk of stroke. These drugs do not rely on blocking serine proteases nor do they require a co-factor (antithrombin III) like unfractionated heparin (UFH) or low molecular weight heparin (LMWH). DTIs are rapid in onset, easy to administer, do not interact with other medications or foods, have limited side effects, and can be administered in a fixed dose. The DTI ximelagatran has already been approved in several European and Asian countries, and over a dozen randomized clinical trials have been conducted demonstrating its performance to be on par with warfarin. However, approval by the FDA in the U.S. remains pending in view of reported incidences of elevations in hepatic enzymes that are currently under evaluation. This review examines the role of DTIs in the prevention and treatment of TED and the recent patents reported in the literature.