The role of recombinant hirudins in the management of thrombotic disorders

Native hirudin is the most potent natural direct thrombin inhibitor currently known; it is capable of inhibiting not only fluid phase, but also clot-bound thrombin. Recombinant technology now allows production of recombinant hirudins (r-hirudins), which are available in sufficient purity and quantity with essentially unaltered thrombin-inhibitory potency. As thrombin is known to play a key role in a number of thrombotic disorders, numerous studies focused on the impact of r-hirudins on the clinical course in these diseases. R-hirudins provided significantly more stable anticoagulation than standard heparin, but demonstrated a relatively narrow therapeutic range with relevant bleeding risk even at clinically effective doses. In doses that are not associated with an increased bleeding risk, r-hirudins often failed to demonstrate significant superiority to heparin. To date, r-hirudins have a definite role in the treatment of heparin-induced thrombocytopenia, where they markedly reduce the high risk of thrombosis. For prophylaxis of deep vein thrombosis, r-hirudins have been shown to be superior to both unfractionated and low molecular weight heparin, but are not extensively used in this indication. In acute coronary syndromes, a definite role of r-hirudins has not yet been firmly established. When applied in an appropriate dose as adjunct to thrombolysis in patients with acute myocardial infarction, randomized, controlled trials did not show a consistent benefit of r-hirudins, especially in the long-term. In patients undergoing coronary balloon angioplasty for acute coronary syndromes, promising effects in the early postprocedural phase did not translate to an improved outcome after 6 months. In patients with unstable angina pectoris, efficacy and safety of r-hirudins as primary antithrombotic therapy are still under debate. In the future, r-hirudins are to be compared with alternative or additional potent antithrombotic agents or treatment strategies. This comparison will ultimately lead to their final placement in the management of thrombotic disorders.