Fondaparinux: a new synthetic and selective inhibitor of Factor Xa.

Fondaparinux (Arixtra) is the first synthetic selective Factor Xa inhibitor. Its efficacy and safety in the prevention of venous thromboembolism (VTE) was first studied in patients undergoing major orthopedic surgery, a setting in the highest risk category for postoperative thrombotic complications. Low-molecular-weight heparins are frequently used in this setting, but the rates of VTE still range between 15% and 33%. In large clinical trials, fondaparinux started 6 hours postoperatively was significantly more effective than enoxaparin in preventing VTE in patients undergoing total hip replacement, total knee replacement or hip fracture surgery. The benefit of extended fondaparinux prophylaxis after hip fracture surgery was also investigated. Other trials have demonstrated that fondaparinux is efficacious in the prevention of VTE in other patient populations at risk of thrombosis and in the treatment of symptomatic VTE.