Thrombin, the ultimate proteinase in the blood coagulation system, acts on diverse substrates and regulates a number of processes related to hemostasis and thrombosis[1]. Thrombin acts in the blood coagulation cascade by catalyzing the conversion of fibrinogen to fibrin and also converting factor XIII to factor XIIIa, which then cross-links the fibrin clot. Thrombin also activates upstream zymogens factors V, VIII, and XI, which then further accelerate the clotting cascade by thrombin synthesis. Thromboembolic disorders are a major cause of mortality in Western societies. At present, clinical treatment of thrombosis involves the administration of heparin and its low molecular weight derivatives or oral anticoagulants of the dicumarol type which all indirectly inhibit the trypsin-like serine protease thrombin[2] .