Hirudin hirudin. Hirudin Hirudin is a naturally occurring peptide in the salivary glands of blood-sucking leeches (such as "Hirudo medicinalis") that has a blood anticoagulant property. This is fundamental for the leeches’ alimentary habit of hematophagy, since it keeps the blood flowing after the initial phlebotomy performed by the worm on the host’s skin. During his years in Birmingham and Edinburgh, John Berry Haycraft had been actively engaged in research and published papers on the coagulation of blood, and in 1884, he discovered that the leech secreted a powerful anticoagulant, which he named hirudin, although it was not isolated until the
Hirudin of thrombin in normal blood circulation is antithrombin. Similar to antithrombin, the anticoagulant activity of hirudin is based on its ability to inhibit the procoagulant activity of thrombin. Hirudin is the most potent natural inhibitor of thrombin. Unlike antithrombin, hirudin binds to and inhibits only the activated thrombin, with a specific activity on fibrinogen. Therefore, hirudin prevents or dissolves the formation of clots and thrombi (i.e., it has a thrombolytic activity), and has therapeutic value in blood coagulation disorders, in the treatment of skin hematomas and of superficial varicose veins, either as an injectable or a topical application cream. In