Advances in thrombolytic therapy.

Streptokinase and urokinase are the two thrombolytic agents currently available in the United States. These drugs promote dissolution of thrombi by stimulating the conversion of plasminogen to plasmin, resulting in an overall "lytic state" in the blood. Recent clinical trials in patients with pulmonary emboli, deep vein thrombosis, arterial thrombosis, and arteriovenous cannula occlusions demonstrated significantly greater lysis with thrombolytics than with heparin alone. However, because of the increased risk of bleeding, the use of these agents is reserved for patients in whom the therapeutic advantages outweigh the disadvantages. Contraindications are numerous and include any preexisting condition that may render the patient more susceptible to bleeding.