Fondaparinux sodium: a selective inhibitor of factor Xa.

The pharmacology and mechanism of action of fondaparinux sodium are described. Fondaparinux sodium is the first agent of a new class of anticoagulants that selectively target factor Xa. It has a linear, dose-dependent pharmacokinetic profile, which provides a highly predictable response. It is 100% bioavailable, has a rapid onset of action, and has a half-life of 14 to 16 hours, allowing for sustained antithrombotic activity over a 24-hour period. The drug does not affect prothrombin time or activated partial thromboplastin time, nor does it affect platelet function or aggregation. Studies in patients with confirmed heparin-induced thrombocytopenia demonstrate that the drug is not associated with in vitro cross-reactivity to heparin antibodies. Fondaparinux sodium appears to meet the criteria for an ideal antithrombotic agent: equal or better effectiveness than currently available agents, a low bleeding risk, no need for laboratory monitoring, and once-daily administration.