Pharmacology · Thrombolytics (fibrinolytics)
Streptokinase !
A streptococcal protein that forms a complex with plasminogen to dissolve clots. Cheap but antigenic and not fibrin-selective.
Updated 2026-11-01
The figure shows the catalytic domain of human plasmin bound to streptokinase, the complex that converts further plasminogen into plasmin.
Mechanism of action
Streptokinase is not an enzyme itself. It binds plasminogen one-to-one and the complex becomes an active plasminogen activator that converts other plasminogen molecules, free or fibrin-bound, into plasmin. Because it is not fibrin-selective it causes a marked systemic lytic state. Being a bacterial protein, it provokes antibodies.
- Streptokinase binds a plasminogen molecule
- The complex activates other plasminogen, free or on fibrin
- Plasmin digests fibrin and fibrinogen
Pharmacokinetics
- Elimination
- Partly neutralised by pre-existing anti-streptococcal antibodies
Indications
- Acute ST-elevation myocardial infarction where fibrin-specific agents or angioplasty are not available Myocardial Infarction (Heart Attack) →
- Pulmonary embolism with haemodynamic instability Pulmonary embolism →
Adverse effects
Common
- Fever and chills
- Allergic reactions
- Bleeding
Contraindications
- Previous intracranial haemorrhage, or a known cerebral vascular lesion or brain tumour
- Active bleeding or a bleeding disorder
- Suspected aortic dissection
- Recent ischaemic stroke, significant head trauma or brain or spinal surgery
- Previous streptokinase exposure or allergy to it
Key interactions
- Heparin, anticoagulants and antiplatelets (aspirin, clopidogrel)
- Add to the bleeding risk; serious haemorrhage is more frequent when heparin is given at the same time
- Warfarin (raised INR)
- Current warfarin use with a raised INR is a relative contraindication
What is monitored
- Neurological status and blood pressure
- Signs of bleeding; haemoglobin and coagulation tests
- Reperfusion: ECG and symptoms in myocardial infarction
- Signs of allergy during the infusion
Administration and safety
- Intravenous infusion; have anaphylaxis treatment ready
- Ask about previous treatment with streptokinase before giving it
Nursing care
- Neurological checks and blood pressure often during and after the infusion; a sudden headache, vomiting or a drop in consciousness suggests intracranial bleeding
- Look for bleeding at puncture sites, gums, urine and stool
- Avoid new arterial punctures, intramuscular injections and unnecessary venepunctures
- Watch for fever, rash, bronchospasm and hypotension during the infusion
Pregnancy and breastfeeding
Pregnancy is a relative contraindication to thrombolysis; it is used only for a life-threatening clot.
Test yourself
Think of the answer, then tap the question to see it.
Is streptokinase an enzyme?
No; it becomes active only after binding plasminogen.
Why is it usually not repeated in the same patient?
Antibodies form, causing allergy and resistance.
Why is its systemic lytic state greater than that of alteplase?
It activates free plasminogen as well as fibrin-bound plasminogen.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Farmacología básica y clínica (Katzung), 16.ª ed., cap. 34 (McGraw Hill, 2025); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 36 (McGraw Hill, 2023); eEML - Electronic Essential Medicines List (World Health Organization, 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.