Thrombin

Also known as coagulation factor II, thrombin is a serine protease that plays a physiological role in regulating hemostasis and maintaining blood coagulation. Once converted from prothrombin, thrombin converts fibrinogen to fibrin, which, in combination with platelets from the blood, forms a clot. Medical thrombin is a protein substance produced through a conversion reaction in which prothrombin of bovine origin is activated by tissue thromboplastin in the presence of calcium chloride. Thrombin requires no intermediate physiological agent for its action. It clots the fibrinogen of the blood directly. Failure to clot blood occurs in the rare case where the primary clotting defect is the absence of fibrinogen itself. Bovine thrombin however, is capable of causing fatal severe bleeding or thrombosis . This thrombosis may result from the development of antibodies against bovine thrombin . Bleeding may result from the development of antibodies against bovine factor V . These antibodies may subsequently cross-react with endogenous human factor V and lead to its deficiency . Patients who are know or suspected to have antibodies to bovine thrombin and/or bovine factor V should not be re-exposed to the product . Patients who are administered bovine thrombin should be monitored for abnormal coagulation laboratory values, bleeding, or indeed, thrombosis . A variety of human thrombin and recombinant thrombin (ie. thrombin alfa) products are available as alternatives to using bovine thrombin.