Bivalirudin: a new promising direct antithrombin.

The deadliest manifestations of ischemic heart disease are initiated and propagated by intra-coronary thrombin generation. Thrombin is resistant to inactivation by heparin when it is bound to fibrin, fibrin degradation products or subendothelial collagen. Recognition of these limitations has led to development of a new class of antithrombin agents which directly target the active sites on the surface of thrombin molecule and are therefore designated as direct antithrombins. These agents do not need mediation of antithrombin III for their action and are not inhibited by platelet factor 4. This report focuses on bivalirudin, a new agent of promising impact on both interventional as well as non-interventional cardiology. It is a short acting anticoagulant which bivalently and directly inhibits thrombin (coagulation factor II). It binds the active (catalytic) site and the fibrinogen-binding site (exosite I). This provides high affinity and specificity for thrombin. Slow cleavage at the Arg3-Pro4 bond results in recovery of thrombin activity after discontinuation of bivalirudin. Bivalirudin inhibits both protease activated receptor 1 and 4 (PAR 1 and PAR 4) thereby effectively inhibiting acute thrombin mediated platelet aggregation. Clinical efficacy has been assessed and proved in over 20 published patient series focussing on patients with acute coronary syndrome with or without myocardial infarction, patients undergoing percutaneous coronary interventions, patients receiving various adjunctive anti-platelet medications, patients with heparin induced thrombocytopenia or patients undergoing cardiac surgery. In contrast to the well established unfractionated heparin, bivalirudin lacks the risk of heparin induced thrombocytopenia. It shows a tendency to lower bleeding risks without reduction of efficacy when compared with the two-pronged treatment with unfractionated heparin and glycoprotein IIb/IIIa inhibitors.