Review and current status of thrombolytic therapy with streptokinase

In 1933 Streptokinase (SK) was isolated from bacterial strains of haemolytic Streptococci. Since then it has become the widest spread drug for fibrinolysis. SK, a protein, consists of 415 aminoacids and has a molecular weight of 47,000u. Together with the plasminogen (PLG) of the blood it forms activator complexes, which then convert other PLG molecules of the blood to plasmin. Plasmin attacks and dissolves fibrin deposits. As a substance produced by bacteria SK stimulates antibody formation in the body, the titer will increase during therapy, and SK lysis should be terminated after 6 days of treatment. Usually SK is administered intravascularly to treat a wide range of diseases, associated with pathological activation of hemostasis, like deep vein thrombosis, pulmonary embolism, myocardial infarction etc.. Contraindications can be traced back to the effects of SK on coagulation and the immune system. Bleeding is the most common side effect, but also a few anaphylactic reactions, caused by massive antigen-antibody precipitation have been observed. The rate of lethality of the treatment was established at 0.7% of the cases. To reduce the incidence of side effects modifications of the drug have been proposed, such as activator complex, light B chain SK, and acylated activator therapy. Compared with Urokinase, SK shows a higher rate of side effects, especially in the field of the immune system. Therapy with Urokinase can be controlled more easily. Nevertheless because of considerable price differences and logistics, SK is preferred in Europe and the USA. If strict guidelines in therapeutic use are followed, the rate of side effects of the drug can be curtailed and will be comparable to those of Urokinase.