Fondaparinux sodium

Fondaparinux sodium was first introduced in the US for prophylaxis of deep vein thrombosis which may lead to pulmonary embolism following major orthopaedic surgery. Fondaparinux is the first of a new class of antithrombic agents distinct from low molecular weight heparin (LMWH) and heparin. This entirely synthetic molecule is a copy of the heparin pentasaccharide sequence, the shortest fragment able to catalyze antithrombin lllmediated inhibition of factor Xa thereby inhibiting thrombin generation without antithrombin action. Fondaparinux does not display significant effects on coagulation tests (such as activated partial thromboplastin time and prothrombin time), does not bind to platelet factor 4 or promote heparin-induced thrombocytopenia. In phase III studies, fondaparinux significantly reduced the incidence of thromboembolism following orthopedic surgery, with an overall risk reduction of 50% in comparison to the LMWH, enoxaparin. Following subcutaneous administration, fondaparinux has a nearly complete bioavailability, a rapid onset of action, a prolonged half-life (17.2 h) enabling once daily dosing and is not metabolized preceeding renal excretion. The drug appears to be generally safe, with haemoragic complications either comparable to or higher than those for LMWH.