Desirudin (Iprivask), a recombinant hirudin, is a parenteral direct thrombin inhibitor approved to prevent venous thromboembolism in patients undergoing elective hip replacement surgery. Desirudin is a potent inhibitor of both clot-bound and freely circulating thrombin. Desirudin acts independently of anti-thrombin, forming a noncovalent irreversible complex with both the active site of thrombin as well as the fibrinogen binding site. This Desirudin–thrombin complex prevents fibrinogen cleavage and other thrombin catalyzed reactions such as the activation of clotting factors V, VIII and XIII, and thrombininduced platelet activation, resulting in a dose-dependent prolongation of activated partial thromboplastin time (aPTT). Desirudin is highly selective and has no effect on plasmin, factors IXa and Xa, tissue plasminogen activator, activated protein C, trypsin, chymotrypsin or complement activation pathways. Bleeding complications reported with the use of desirudin in patients undergoing hip-replacement surgery are similar to those reported with heparin and enoxaparin.