Streptokinase

Biofactor streptokinase is a highly purified streptokinase derived from β haemolytic streptococci of Lancefield group C. The activation of the endogenous fibrinolytic system is initiated by the formation of a streptokinase-plasminogen complex.

This complex possesses activator properties and converts plasminogen into the proteolytic and fibrinolytic active plasmin. The more plasminogen that is bound within this activator complex, the less plasminogen is left to be converted into its enzymatically active form. Therefore, high doses of streptokinase are associated with a lower bleeding risk and vice versa.

After intravenous administration and neutralisation of the individual antistreptokinase-antibody titre, streptokinase is immediately available systemically for activation of the fibrinolytic system.

Streptokinase has a very short half-life. The first rapid clearance from the plasma is due to the formation of the complex between streptokinase and streptokinase antibody. This complex is biochemically inert and is cleared rapidly from the circulation. Once the antibody has been neutralised, the streptokinase activates the plasminogen as described above.

The elimination kinetics of streptokinase follows a biphasic course. A small proportion of the dose is bound to anti-streptokinase antibodies and metabolised with a half-life of 18 minutes while most of it forms a streptokinase-plasminogen activator complex and is biotransformed with a half-life of about 80 minutes.

Peak fibrinolytic activity is found in the blood about 20 minutes after dosing.

Like other proteins, streptokinase is metabolised proteolytically in the liver and eliminated via the kidneys. Animal data suggest that streptokinase may also be excreted unchanged in the bile.

In an Ames Test on biofactor streptokinase, no evidence of mutagenic potential was found. No other preclinical safety studies have been performed on biofactor streptokinase.