How do streptokinase, urokinase, and tissue plasminogen activator dissolve blood clots?

Streptokinase, urokinase, and tissue plasminogen activator (t-PA) are fibrinolytic drugs that dissolve blood clots by activating the body's fibrinolytic pathway. Their primary function is to convert plasminogen, an inert precursor protein, into plasmin, the active enzyme responsible for degrading fibrin and dissolving the clot.12

Each agent operates with different mechanisms and specificities:

• Streptokinase: Produced from Streptococcus bacteria, this agent activates plasminogen systemically. While effective at reestablishing blood flow, it can cause the breakdown of other coagulation factors, which may lead to systemic bleeding.1
• Urokinase: A protease enzyme derived from human kidney cell cultures, it activates plasminogen directly. It is used to lyse recently formed pulmonary emboli and generally causes less extensive breakdown of coagulation factors than streptokinase.1
• Tissue plasminogen activator (t-PA): This agent is highly selective; it binds readily to fibrin and primarily activates plasminogen that is already bound to the clot. This targeted action allows for clot dissolution with minimal systemic breakdown of coagulation factors, offering significant advantages in treating coronary thrombosis.1