Pharmacokinetics of streptokinase in patients based on amidolytic activator complex activity

The purpose of this study was to determine the pharmacokinetics of intravenous streptokinase in humans. Five patients with myocardial infarction, six patients with venous thromboembolism, and two normal volunteers were studied. The patients with myocardial infarction received 500,000 U over 30 minutes, the patients with venous thromboembolism received 250,000 U over 30 minutes followed by 100,000 U/hr over 16 to 78 hours, and the normal volunteers received 100,000 U over 15 minutes. Plasma streptokinase levels were measured based on the amidolytic activity of the streptokinase-plasminogen complex on the chromogenic substrate S-2251. Pharmacokinetic parameters were: biologic half-life 82 +/- 25 minutes, total clearance 10.8 +/- 8.8 ml/min, and apparent volume of distribution 1.10 +/- 0.71 l. Streptokinase levels declined progressively during the continuous, prolonged infusion in the patients with venous thromboembolism over 60 hours of treatment. We conclude that there are distinct time-dependent changes in the pharmacokinetics of streptokinase during continuous intravenous infusion and that this phenomenon is likely to be associated with progressively decreasing thrombolytic efficacy.