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tPA Dose for Ischemic Stroke Calculator

Calculates weight-based alteplase (tPA) total dose, IV bolus, and infusion for acute ischemic stroke per AHA/ASA guidelines

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Why use it

Accurate weight-based dosing of alteplase is critical — overdosing increases the risk of symptomatic intracranial hemorrhage (sICH), the most devastating complication of IV thrombolysis (2–8% risk), while underdosing reduces reperfusion efficacy. The maximum dose cap of 90 mg ensures that obese patients do not receive excessive doses. This calculator computes the total dose, bolus, and infusion components instantly and flags when the weight-cap applies, supporting safe, protocol-compliant administration in a time-pressured emergency setting.

About

Intravenous alteplase (recombinant tissue plasminogen activator, rt-PA) remains the only FDA-approved pharmacological reperfusion therapy for acute ischemic stroke, based on the pivotal NINDS rt-PA Stroke Trial published in the New England Journal of Medicine in 1995. The standard dosing regimen is 0.9 mg/kg intravenously, with a maximum total dose of 90 mg regardless of body weight. The dose is divided as follows: 10% of the total calculated dose is administered as an intravenous bolus over 1 minute, followed by the remaining 90% as a continuous intravenous infusion over 60 minutes. The treatment window was originally established as 0–3 hours from symptom onset; subsequent evidence from the ECASS III trial extended the window to 3–4.5 hours in selected patients. The 2019 AHA/ASA Guidelines for the Early Management of Acute Ischemic Stroke (Powers et al.) provide the current standard of care, including extended indications for thrombolysis in patients with wake-up stroke and unknown onset time using advanced neuroimaging (DWI-FLAIR mismatch). Tenecteplase (TNK-tPA) 0.25 mg/kg IV (max 25 mg) administered as a single bolus is an emerging alternative endorsed in the 2023 AHA/ASA Focused Update as a reasonable alternative to alteplase in patients with no major early ischemic changes and who are also eligible for thrombectomy, though alteplase remains the most widely used agent.

When to use

  • Adult patients with acute ischemic stroke presenting within 3 hours of symptom onset (or last-known-well time)
  • Patients with stroke onset 3–4.5 hours ago who meet ECASS III extended-window criteria (age <80, NIHSS ≤25, no prior combined stroke + diabetes, no anticoagulant use)
  • Wake-up strokes or unknown-onset strokes with DWI-FLAIR mismatch on MRI (AHA/ASA 2019 IIa recommendation)
  • As part of bridging therapy before mechanical thrombectomy in large vessel occlusion (LVO) — IV tPA given while thrombectomy team is mobilized
  • NOT for use without first confirming: (1) CT/MRI excludes intracranial hemorrhage; (2) BP controlled <185/110 mmHg; (3) no major contraindications to thrombolysis
  • NOT for pediatric stroke — dosing and evidence base differ; consult pediatric neurology

Formula

ALTEPLASE DOSE: Total dose (mg) = 0.9 × weight (kg) [Maximum: 90 mg] IV Bolus = 10% of total dose [Maximum: 9 mg] — over 1 minute IV Infusion = 90% of total dose [Maximum: 81 mg] — over 60 minutes Weight cap: Patients ≥100 kg → Total dose = 90 mg (cap applies) Patients <100 kg → Total dose = 0.9 × weight TENECTEPLASE (alternative, single bolus): Dose = 0.25 mg/kg [Maximum: 25 mg] — over 5 seconds

Pearls & pitfalls

  • The maximum dose is 90 mg TOTAL regardless of body weight — patients weighing >100 kg all receive 90 mg (9 mg bolus + 81 mg infusion). Entering weight >100 kg will not increase the dose beyond the cap.
  • The 10%/90% split is calculated from the TOTAL dose: bolus = 0.09 mg/kg (max 9 mg); infusion = 0.81 mg/kg (max 81 mg). Common dosing errors occur when the bolus is calculated separately from body weight rather than as 10% of the total dose already computed.
  • Blood pressure MUST be below 185/110 mmHg before tPA administration and maintained below 180/105 mmHg during and for 24 hours after — labetalol 10–20 mg IV over 1–2 min (repeat once) or nicardipine infusion 5–15 mg/hr are first-line agents.
  • Time is brain — for every 1-minute reduction in door-to-needle time, an additional 1.8 days of healthy life are gained on average. The AHA target is door-to-needle ≤60 minutes (benchmark ≤45 min).
  • Tenecteplase 0.25 mg/kg IV (max 25 mg) as a single bolus is endorsed as a reasonable alternative (Class IIa) by the 2023 AHA/ASA Focused Update for patients with LVO being considered for thrombectomy — it is easier to administer and allows faster mobilization.
  • Symptomatic intracranial hemorrhage (sICH) occurs in approximately 2–8% of treated patients. Risk is higher with: higher NIHSS, hyperglycemia (glucose >180 mg/dL), older age, CT early ischemic changes (>1/3 MCA territory), and uncontrolled hypertension.
  • The NIHSS should be documented before tPA administration — it serves as the baseline for monitoring improvement or deterioration and is required for treatment decisions in the extended window.
  • Fibrinogen levels and platelet counts should be checked, but should NOT delay tPA administration if the clinical assessment supports treatment and there is no known coagulopathy.
  • If a patient was on a DOAC within the prior 48 hours (or renally-adjusted interval for dabigatran), IV tPA is generally contraindicated unless a specific reversal agent has been given and drug levels are confirmed undetectable.

Next steps

Administer alteplase as calculated: bolus over 1 minute followed by infusion over 60 minutes through a dedicated IV line. Monitor blood pressure every 15 minutes during infusion, then every 30 minutes for 6 hours, then every 60 minutes for 16 hours. Target BP <180/105 mmHg during and after infusion. No anticoagulants or antiplatelet agents for 24 hours post-tPA (unless mechanical thrombectomy performed — then per interventional team). Repeat neurological examination every 15 minutes during infusion. If neurological deterioration occurs: STOP infusion immediately and obtain urgent non-contrast CT to evaluate for hemorrhagic transformation. Admit to stroke unit or neurocritical care unit. Repeat CT or MRI at 24 hours before initiating antiplatelet therapy.

Evidence

NINDS rt-PA Stroke Study Group. Tissue plasminogen activator for acute ischemic stroke. N Engl J Med. 1995;333(24):1581-1587. PMID:7477192. Pivotal RCT establishing benefit of alteplase 0.9 mg/kg (max 90 mg) within 3h. Hacke W et al. (ECASS III). Thrombolysis with alteplase 3 to 4.5 hours after acute ischemic stroke. N Engl J Med. 2008;359(13):1317-1329. PMID:18815396. Extended window to 4.5h in selected patients. Powers WJ et al. 2019 AHA/ASA Guidelines for the Early Management of Patients with Acute Ischemic Stroke. Stroke. 2019;50(12):e344-e418. PMID:31662037. Current gold standard guidelines. Khatri P et al. Good clinical outcome after ischemic stroke with successful revascularization is time-dependent. Neurology. 2009;73(13):1066-1072 — time-is-brain evidence.

References

  1. NINDS rt-PA Stroke Study Group. Tissue plasminogen activator for acute ischemic stroke. N Engl J Med. 1995;333(24):1581-1587. — link
  2. Hacke W et al. (ECASS III). Thrombolysis with alteplase 3 to 4.5 hours after acute ischemic stroke. N Engl J Med. 2008;359(13):1317-1329. — link
  3. Powers WJ et al. 2019 AHA/ASA Guidelines for the Early Management of Patients with Acute Ischemic Stroke. Stroke. 2019;50(12):e344-e418. — link
  4. Goyal M et al. 2023 AHA/ASA Focused Update on Tenecteplase Use in Acute Ischemic Stroke. Stroke. 2024. — link
  5. Marler JR et al. Earlier treatment associated with better outcome in the NINDS t-PA stroke study. Neurology. 2000;55(11):1649-1655. — link