What is the most serious risk of alteplase?

Bleeding, particularly symptomatic intracranial haemorrhage, which can be fatal. This is why strict eligibility screening and time windows are enforced.

Why does the timing of alteplase matter so much in stroke?

Benefit is greatest when given soon after symptom onset and declines with delay, while haemorrhage risk persists, so it is generally limited to within 4.5 hours.

Who cannot receive alteplase?

People with active bleeding, recent surgery or head trauma, prior brain haemorrhage, recent stroke, intracranial tumours or aneurysms, or severely uncontrolled blood pressure, among other contraindications.

Can alteplase be used at home or self-administered?

No. It is an emergency intravenous drug requiring hospital monitoring, imaging to exclude haemorrhage, and immediate management of bleeding complications.

EMA-approvedaka Activase, rt-PA

Alteplase — Complete Research Guide (2026)

Last updated 2026-06-30

TL;DR

Alteplase (also known as Activase) is a peptide catalogued under Enzymes (Recombinant tPA). Documented context: Ischemic stroke; MI; PE. Neutral reference entry; EU status: EU-approved prescription medicine.

What is Alteplase?

Alteplase (recombinant tissue plasminogen activator, rt-PA; brand Activase, and Actilyse outside the US) is an FDA- and EMA-approved intravenous fibrinolytic, not a research chemical.

It is approved for acute ischaemic stroke, acute ST-elevation myocardial infarction (STEMI), and acute massive or haemodynamically unstable pulmonary embolism, and a low-dose form (Cathflo Activase) clears occluded catheters.

Evidence is high-quality: its approvals rest on large randomised controlled trials in humans, most famously the 1995 NINDS stroke trial.

How does Alteplase work?

Alteplase is a recombinant version of human tissue plasminogen activator that binds fibrin within a clot and converts entrapped plasminogen to plasmin, the enzyme that degrades fibrin and dissolves the thrombus.

This fibrin-selective activation localises clot breakdown, though at therapeutic doses systemic plasmin generation still lowers fibrinogen and raises bleeding risk.

What does the research say about Alteplase?

In acute ischaemic stroke treated within 3 hours of onset, intravenous alteplase increased the proportion of patients with minimal or no disability at 3 months. ^[1]
The benefit of alteplase in ischaemic stroke extends to a 3-to-4.5-hour treatment window, though with a lower magnitude of effect than earlier treatment. ^[2]
Across pooled stroke trials, earlier treatment produced greater benefit, and net benefit was seen up to about 4.5 hours regardless of age or stroke severity. ^[5]

Clinical research & studies

The references below are the primary sources cited throughout this guide. Each links directly to PubMed or the regulator. Where evidence is preclinical (animal or in-vitro), that is stated rather than implied.

[1] Tissue plasminogen activator for acute ischemic stroke — The National Institute of Neurological Disorders and Stroke rt-PA Stroke Study Group, The New England Journal of Medicine 1995. (Randomised controlled trial)
[2] Thrombolysis with alteplase 3 to 4.5 hours after acute ischemic stroke — Hacke W et al., The New England Journal of Medicine 2008. (Randomised controlled trial (ECASS III))
[3] An international randomized trial comparing four thrombolytic strategies for acute myocardial infarction — The GUSTO Investigators, The New England Journal of Medicine 1993. (Randomised controlled trial (GUSTO-I))
[4] The benefits and harms of intravenous thrombolysis with recombinant tissue plasminogen activator within 6 h of acute ischaemic stroke (the third international stroke trial [IST-3]): a randomised controlled trial — IST-3 collaborative group, Lancet 2012. (Randomised controlled trial)
[5] Effect of treatment delay, age, and stroke severity on the effects of intravenous thrombolysis with alteplase for acute ischaemic stroke: a meta-analysis of individual patient data from randomised trials — Emberson J et al., Lancet 2014. (Individual-patient-data meta-analysis)

Dosing context

This is not medical advice or a usage recommendation. Dosing figures are reported research context only, cited from the published literature.

Alteplase is a hospital-only emergency medicine: the ischaemic-stroke regimen (0.9 mg/kg, maximum 90 mg, 10% as a bolus then the remainder over 60 minutes) is administered strictly within 4.5 hours of symptom onset by trained clinicians.

Myocardial-infarction and pulmonary-embolism regimens differ and are weight- and indication-specific; this is context only and not a guide for use.

Side effects & safety profile

The dominant and potentially fatal risk is bleeding, especially symptomatic intracranial haemorrhage; the NINDS trial reported roughly a tenfold higher rate of symptomatic brain haemorrhage versus placebo in stroke patients.

Absolute contraindications include active internal bleeding, recent intracranial surgery or serious head trauma, prior intracranial haemorrhage, recent ischaemic stroke, intracranial neoplasm or aneurysm, and severe uncontrolled hypertension.

It must be given only under emergency medical supervision with strict eligibility screening; benefit falls and haemorrhage risk rises as the time window is exceeded.

Stacking & combinations

In cardiac and stroke protocols alteplase is combined with antiplatelet and/or anticoagulant therapy under strict physician control, which further increases bleeding risk and is not a self-directed stack.

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Frequently asked questions

It is a fully approved prescription fibrinolytic (Activase/Actilyse), used in hospitals for acute ischaemic stroke, STEMI, and massive pulmonary embolism. It is not a research-only compound.

References

[1] Tissue plasminogen activator for acute ischemic stroke — The National Institute of Neurological Disorders and Stroke rt-PA Stroke Study Group, The New England Journal of Medicine 1995. PMID: 7477192. View sourceStudy: Randomised controlled trialIntravenous alteplase within 3 hours of ischaemic stroke onset improved 3-month functional outcome despite increased symptomatic intracranial haemorrhage.
[2] Thrombolysis with alteplase 3 to 4.5 hours after acute ischemic stroke — Hacke W et al., The New England Journal of Medicine 2008. PMID: 18815396. View sourceStudy: Randomised controlled trial (ECASS III)Alteplase given 3 to 4.5 hours after stroke onset improved outcomes versus placebo, extending the treatment window.
[3] An international randomized trial comparing four thrombolytic strategies for acute myocardial infarction — The GUSTO Investigators, The New England Journal of Medicine 1993. PMID: 8204123. View sourceStudy: Randomised controlled trial (GUSTO-I)Accelerated alteplase reduced 30-day mortality in acute myocardial infarction compared with streptokinase-based strategies.
[4] The benefits and harms of intravenous thrombolysis with recombinant tissue plasminogen activator within 6 h of acute ischaemic stroke (the third international stroke trial [IST-3]): a randomised controlled trial — IST-3 collaborative group, Lancet 2012. PMID: 22632908. View sourceStudy: Randomised controlled trialAlteplase increased early haemorrhagic risk but was associated with improved functional outcome in a broad stroke population, supporting early treatment.
[5] Effect of treatment delay, age, and stroke severity on the effects of intravenous thrombolysis with alteplase for acute ischaemic stroke: a meta-analysis of individual patient data from randomised trials — Emberson J et al., Lancet 2014. PMID: 25106063. View sourceStudy: Individual-patient-data meta-analysisEarlier alteplase treatment yielded greater benefit, with net benefit up to about 4.5 hours irrespective of age or severity.

This article is for educational and research purposes only. Peptides discussed here are not approved for human consumption by the FDA, EMA, or equivalent regulators outside of specific clinical contexts. Always consult a licensed medical professional before any therapeutic use.