An acylated inactive complex of streptokinase and human lysine-plasminogen. After injection, the acyl group is slowly hydrolyzed, producing an activator that converts plasminogen to plasmin, thereby initiating fibrinolysis. Its half-life is about 90 minutes compared to 5 minutes for TPA; (TISSUE PLASMINOGEN ACTIVATOR); 16 minutes for URINARY PLASMINOGEN ACTIVATOR and 23 minutes for STREPTOKINASE. If treatment is initiated within 3 hours of onset of symptoms for acute myocardial infarction, the drug preserves myocardial tissue and left ventricular function and increases coronary artery patency. Bleeding complications are similar to other thrombolytic agents.