All of the so-called thrombolytic (more specifically, fibrinolytic) agents are either direct or indirect activators of plasminogen, a circulating fibrinolytic proenzyme (61). Plasminogen is converted by plasminogen activators or activator complexes to plasmin, the active fibrinolytic enzyme form, by cleavage of the arginine 560-valine 561 bond. Plasmin has relatively broad proteolytic properties, degrading fibrin, fibrinogen, pro-thrombin, and factors V and VII. Plasminogen activator-induced fibrinolysis may then act to disrupt forming thrombus and lead to reperfusion.
Six thrombolytic agents have been approved and marketed for use in the United States, although UK is approved only for IC delivery. These agents differ in several properties, including structure, fibrin specificity, speed and duration of action, and anti-genicity, as summarized in Table 1.
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