Fondaparinux: basic properties and efficacy and safety in venous thromboembolism prophylaxis.

The synthetic pentasaccharide fondaparinux is the first in a novel class of antithrombotic agents. By selectively inactivating factor Xa in an antithrombin-dependent mechanism of action, fondaparinux exerts its anticoagulant effect through inhibition of thrombin generation, without any direct effect on thrombin activity. Unlike unfractionated heparin and low-molecular-weight heparins, fondaparinux is a single molecular entity produced by total chemical synthesis. Its favorable pharmacokinetic profile and pharmacodynamics allow for safe and effective once-daily dosing in the majority of populations. Initial clinical development of fondaparinux has focused on the prevention of venous thromboembolism following major orthopedic surgery--that is, hip and knee replacement and hip fracture. Results of the largest phase III clinical trial program to date in these major hip and knee surgeries demonstrate comparable safety, in terms of clinically relevant bleeding, and an overall 55% reduction in risk of venous thromboembolism with fondaparinux relative to the low-molecular-weight heparin enoxaparin.