Hirudin
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sheng Shi, M.D. [2]
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Overview
Iprivask® (desirudin for injection) is a specific inhibitor of human thrombin. It has a protein structure that is similar to that ofHirudin, the naturally occurring anticoagulant present in the peripharyngeal glands in the medicinal leech, Hirudo medicinalis. Hirudin is a single polypeptide chain of 65 amino acids residues and contains three disulfide bridges. Desirudin has a chemical formula of C287H440N80O110S6 with a molecular weight of 6963.52. Desirudin, which is expressed in yeast (Saccharomyces cerevisiae,strain TR 1456) by recombinant DNA technology differs from the naturalHirudin by lack of a sulfate group on Tyr-63. The biological activity of desirudin is determined through a chromogenic assay which measures the ability of desirudin to inhibit the hydrolysis of a chromogenic peptidic substrate by thrombin in comparison to a desirudin standard. One vial of desirudin contains 15.75 mg desirudin corresponding to approximately 315,000 antithrombin units (ATU) or 20,000 ATU per milligram of desirudin with reference to the WHO International Standard (prepared 1991) for alphathrombin.
Category
Anticoagulants:Direct thrombin (II) inhibitors
US Brand Names
IPRIVASK
FDA Package Insert
| Indications and Usage | Dosage and Administration | Contraindications | Warnings and Precautions | Adverse Reactions | Drug Interactions | Use in Specific Populations | Overdosage | Description | Clinical Pharmacology | Nonclinical Toxicology | Clinical Studies | How Supplied/Storage and Handling | Labels and Packages
Mechanism of Action
Desirudin is a selective inhibitor of free circulating and clot-bound thrombin. The anticoagulant properties of desirudin are demonstrated by its ability to prolong the clotting time of human plasma. One molecule of desirudin binds to one molecule of thrombin and thereby blocks the thrombogenic activity of thrombin. As a result, all thrombin-dependent coagulation assays are affected. Activated partial thromboplastin time (aPTT) is a measure of the anticoagulant activity of desirudin and increases in a dose-dependent fashion. The pharmacodynamic effect of desirudin on proteolytic activity of thrombin was assessed as an increase in aPTT. A mean peak aPTT prolongation of about 1.38 times baseline value (range 0.58 to 3.41) was observed following subcutaneous b.i.d. injections of 15 mg desirudin. Thrombin time (TT) frequently exceeds 200 seconds even at low plasma concentrations of desirudin, which renders this test unsuitable for routine monitoring of Iprivask therapy. At therapeutic serum concentrations, desirudin has no effect on other enzymes of the hemostatic system such as factors IXa, Xa, kallikrein, plasmin, tissue plasminogen activator, or activated protein C. In addition, it does not display any effect on other serine proteases, such as the digestive enzymes trypsin, chymotrypsin, or on complement activation by the classical or alternative pathways.