Fondaparinux is a synthetic and specific inhibitor of activated Factor X (Xa). By selectively binding to antithrombin III (ATIII), fondaparinux sodium potentiates (about 300 times) the innate neutralization of Factor Xa by ATIII. Neutralization of Factor Xa interrupts the blood coagulation cascade and thus inhibits thrombin formation and thrombus development. Fondaparinux is indicated for the prophylaxis of deep vein thrombosis (DVT), which may lead to pulmonary embolism (PE): in patients undergoing hip fracture surgery, including extended prophylaxis; in patients undergoing hip replacement surgery; in patients undergoing knee replacement surgery; in patients undergoing abdominal surgery who are at risk for thromboembolic complications. The most serious adverse reactions reported with Fondaparinux are bleeding complications and thrombocytopenia. Agents that may enhance the risk of hemorrhage should be discontinued prior to initiation of therapy with Fondaparinux unless these agents are essential.