Pharmacology · Class
Thrombolytics (fibrinolytics) !
Drugs that dissolve a clot that is already blocking a vessel, by turning plasminogen into plasmin. Bleeding is their main risk.
Updated 2026-11-01
What they are
Plasminogen activators given intravenously in acute ST-elevation myocardial infarction, acute ischaemic stroke and massive pulmonary embolism. Recombinant tissue plasminogen activator (alteplase) and its engineered variants (tenecteplase, reteplase) prefer fibrin-bound plasminogen; streptokinase, a bacterial protein, does not.
Mechanism of action
They convert plasminogen into plasmin, a protease that digests the fibrin mesh of the thrombus. At therapeutic levels plasmin also degrades fibrinogen and factors V and VIII and dissolves the fibrin of normal haemostatic plugs, which is why haemorrhage, above all intracranial, is the main toxicity.
Target: Plasminogen → plasmin
Drugs in this class
- AlteplaseRecombinant tissue plasminogen activator that dissolves the clot in acute ischaemic stroke, heart attack and massive…Plasminogen (the zymogen of plasmin), bound to fibrin
- TenecteplaseAn engineered tissue plasminogen activator that lasts longer than alteplase, so it is given as a single bolus in heart…Plasminogen (the zymogen of plasmin), bound to fibrin
- ReteplaseA shortened recombinant tissue plasminogen activator with a longer half-life, given as two boluses in acute myocardial…Plasminogen (the zymogen of plasmin), bound to fibrin
- StreptokinaseA streptococcal protein that forms a complex with plasminogen to dissolve clots. Cheap but antigenic and not…Plasminogen (streptokinase–plasminogen activator complex)
Others in the class
- urokinase
Test yourself
Think of the answer, then tap the question to see it.
Which enzyme do all thrombolytics end up generating?
Plasmin, from plasminogen.
What is the most feared adverse effect of thrombolysis?
Intracranial haemorrhage.
Why does alteplase cause less systemic plasmin than streptokinase?
It activates plasminogen mainly when both are bound to fibrin in the clot.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 36 (McGraw Hill, 2023); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 34 (McGraw Hill, 2025); Alteplase Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.