Rivaroxaban.: Factor Xa inhibitor, anticoagulant.

Regulation of excessive coagulation through inhibition of activated serine proteases has proven to be a successful strategy for the prevention of thrombotic complications. Unfractionated heparin (UH) and low-molecular-weight heparins (LMWHs) bind to antithrombin III (ATIII) and accelerate the ability of this enzyme to inhibit activated serine proteases, thus reducing the overall activation of the coagulation cascade. Rivaroxaban (Bay-59-7939) is an oral, direct factor Xa (FXa) inhibitor developed by Bayer which belongs to a new class of small-molecule, active site-directed FXa inhibitors. Rivaroxaban does not require plasma cofactors to exert its regulatory effect on coagulation and it does not interfere with other serine proteases. Rivaroxaban demonstrated excellent in vivo antithrombotic activity in preliminary studies in animal models, with maximal inhibition of FX activity approximately 3 h after oral dosing. In pharmacolkinetic studies, the drug was rapidly absorbed and eliminated. In vitro and clinical studies suggested that drug-drug interactions are unlikely. Two major studies have evaluated the efficacy and safety of rivaroxaban in the prophylaxis of thrombosis in patients undergoing orthopedic surgery. In these studies, rivaroxaban (2.5-10 mg b.i.d.) compared favorably with enoxaparin (40 mg once daily).