Fondaparinux sodium is structurally close to heparin with only one more sulfate group. It is a selective factor Xa inhibitor which, by binding to antithrombin III, results in less thrombin formation and less thrombus growth. It is therefore used as an anticoagulant and antithrombotic. It is approved for the prophylaxis of thrombosis and pulmonary embolism in patients after major orthopedic surgery, as well as general surgical and medical patients. It is also used to treat deep vein thrombosis and pulmonary embolism, thrombophlebitis of the lower extremities, various infarcts and unstable angina pectoris.