Fibrinolysis and its current usage.

By activating plasminogen into plasmin, which in turn dissolves fibrin, fibrinolytic agents can dissolve pathologic thrombi. Streptokinase, a fibrinolytic agent derived from group C beta-hemolytic streptococci, is antigenic and can elicit allergic reactions. Urikinase, a fibrinolytic agent obtained by purification from human urine or from human fetal kidney cell culture, is not antigenic, and for this reason can be used repeatedly, if needed, whereas streptokinase cannot be used for retreatment within six months of a course of therapy. Either agent can be introduced into the circulation systemically (intravenously) or locally (via catheter). The indications for systemic therapy include deep-vein thrombosis, pulmonary embolism, and arterial thrombosis and embolism. The indications for local therapy include acute myocardial infarction, arterial thrombosis and embolism, and the clearing of occluded arteriovenous cannulae and access shunts. Contraindications include an actively bleeding lesion, a vascular intracranial disorder, or uncontrolled hypertension; relative contraindications include pregnancy; a recent wound, fracture, surgery, or deep closed biopsy; or a general contraindication to anticoagulation, such as coagulopathy, uremia, or severe liver disease. During thrombolytic therapy, invasive procedures, intramuscular injections, and the use of other anticoagulant or antiplatelet agents should be avoided. Measurement of fibrinogen levels, the titer of fibrin/fibrinogen degradation product, or thrombin time can be used to monitor therapy.