Urokinase has a complex mechanism of action. It is an enzyme protein isolated from the urine of healthy people or obtained from human kidney tissue culture. It is composed of two parts with molecular weights of 33000 and 54000 respectively. This product direct effects on endogenous fibrinolysis system, which can catalytic cracking fibrinolytic enzyme into a fibrinolytic enzyme, which can not only degradation of fibrin clot, also can degrade fibrinogen in blood, and clotting factor Ⅴ and blood coagulation factor Ⅷ etc, so as to play a role of thrombolysis.

　　The goods can direct effects on endogenous fibrinolysis system into a fibrinolytic enzyme catalytic cracking fibrinolytic enzyme, which can not only degradation of fibrin clot, also can degrade fibrinogen in blood, and clotting factor Ⅴ and blood coagulation factor Ⅷ etc, so as to play a role of thrombolysis. The product has quick and good effect on the newly formed thrombus. The product can also improve the activity of vascular ADP enzyme, inhibit adp-induced platelet aggregation, and prevent thrombosis. After intravenous infusion, the fibrinolytic enzyme activity in the patients increased significantly. Take it off for a few hours，After that, the fibrinolytic activity returned to its original level, but the reduction of plasma fibrin or fibrinogen levels and the increase of their degradation products lasted for 12-24 hours. The results showed that the thrombolytic effect was significantly correlated with the dosage and time window of administration. The toxicity was very low, and the lethal dose of intravenous injection of half of the mice was more than 1 million ius/kg body weight. There was no obvious antigenicity, teratogenicity, carcinogenicity or mutagenicity. There are few reports of anaphylaxis in clinical application. However, in view of the increased fibrinolytic activity of this product, the blood circulation was reducedThe unbound plasminogen and fibrinogen bound to fibrin in the ring may present a risk of severe bleeding.

　　After intravenous urokinase injection, the activity of fibrinolytic enzyme increased rapidly, peaked at 15min, and continued to increase after 6h. Fibrinogen decreased to about 1000mg/L, and slowly recovered to normal after 24h. Urokinase is metabolized in the liver, and its half-life in vivo is about 20min. The half-life of patients with liver dysfunction is somewhat prolonged. Small amounts of the drug are excreted in bile and urine.