How this instrument works
Alteplase (tissue plasminogen activator, tPA) is the clot-dissolving medication given intravenously to eligible patients with acute ischemic stroke within the guideline-specified treatment window. Because faster treatment is strongly associated with better outcomes in eligible patients, stroke teams work the dose out quickly once a patient is confirmed eligible — this calculator does that one step, translating a weight in kilograms into the total dose, bolus, and infusion amounts in milligrams.
The standard regimen is 0.9 mg per kilogram of body weight, with a fixed ceiling of 90 mg total regardless of how much heavier than roughly 100 kg the patient is. Ten percent of that total dose is given as an initial intravenous bolus over one minute, and the remaining 90 percent is infused continuously over the following 60 minutes. Both the total-dose cap and the bolus/infusion split come from the pivotal NINDS trial protocol and are carried forward in the current AHA/ASA guideline and the FDA prescribing information for alteplase.
This is explicitly a hospital, time-critical, clinician-administered medication decision — alteplase for stroke is given under close monitoring by a stroke team after imaging has ruled out hemorrhage and eligibility criteria (time since symptom onset, blood pressure, coagulation status, and a list of exclusion criteria) have been checked. This calculator handles only the weight-to-dose arithmetic; it does not assess eligibility, contraindications, or timing, all of which require full clinical evaluation.
- Enter the patient's weight in kilograms.
- Read the total alteplase dose in mg (0.9 mg/kg, capped at 90 mg).
- Read the initial IV bolus in mg, given over 1 minute.
- Read the remaining infusion in mg, given over the following 60 minutes.
Worked example — 70 kg patient
A 70 kg patient's weight-based dose is 70 × 0.9 = 63 mg, well under the 90 mg cap, so the total dose is 63 mg. Ten percent of that, 6.3 mg, is given as an IV bolus over 1 minute, and the remaining 90 percent, 56.7 mg, is infused over the following 60 minutes.
For a heavier 120 kg patient, the uncapped weight-based figure would be 120 × 0.9 = 108 mg, but the fixed 90 mg ceiling applies instead, so the total dose stays at 90 mg — a 9 mg bolus and an 81 mg infusion — regardless of how far the patient's weight sits above the roughly 100 kg point where the cap takes over. A lighter 50 kg patient's total dose is 50 × 0.9 = 45 mg, split into a 4.5 mg bolus and a 40.5 mg infusion.
Questions
Why is the alteplase dose capped at 90 mg?
The pivotal NINDS trial that established IV alteplase's benefit in acute ischemic stroke used a 0.9 mg/kg dosing regimen with a fixed 90 mg ceiling, and that same cap has carried forward into current AHA/ASA guidelines and the FDA prescribing information. Because the trial evidence for both efficacy and bleeding risk was generated using that capped regimen, clinicians dose according to the same cap rather than extrapolating an uncapped weight-based dose for heavier patients.
Why is only part of the dose given as a bolus?
The regimen gives 10% of the total dose as an immediate IV bolus over 1 minute to begin thrombolysis quickly, then infuses the remaining 90% over the next 60 minutes. This split, like the dose itself, comes from the trial protocol that established alteplase's use in acute ischemic stroke and is specified in current guidelines and prescribing information.
Is this calculator meant for a patient or caregiver to use?
No. IV alteplase for stroke is administered only in a hospital setting by a clinical team after imaging, eligibility screening, and informed consent, with close monitoring for bleeding complications throughout and after the infusion. This calculator performs only the weight-to-dose arithmetic described in guidelines; it does not determine whether a patient is eligible for treatment, and it is not intended for use outside a clinical setting.
Does this calculator check eligibility criteria for alteplase?
No. Eligibility for IV alteplase depends on factors this calculator does not evaluate — time since symptom onset relative to the guideline-specified treatment window, blood pressure, blood glucose, coagulation status and current anticoagulant use, imaging findings ruling out hemorrhage, and a detailed list of exclusion criteria in the AHA/ASA guideline. This tool only converts a confirmed, eligible patient's weight into the corresponding dose.
What guideline or source is the dosing based on?
The 0.9 mg/kg dose, 90 mg cap, and 10%/90% bolus-infusion split are specified in the 2019 AHA/ASA Guideline for the Early Management of Patients with Acute Ischemic Stroke (Powers WJ et al., Stroke. 2019;50(12):e344-e418) and in the FDA-approved prescribing information for Activase (alteplase), both of which trace the regimen back to the original NINDS trial protocol.
Is alteplase the same as tenecteplase?
No — they are different thrombolytic drugs. Alteplase (tPA) is the medication and dosing regimen (0.9 mg/kg, capped at 90 mg, bolus plus infusion) this calculator covers, while tenecteplase is a related but distinct thrombolytic increasingly used in some stroke centers with a different, single-bolus dosing regimen. The two are not interchangeable using this calculator's numbers.
References
- Powers WJ, Rabinstein AA, Ackerson T, et al. — 2019 Update to the 2018 AHA/ASA Guideline for the Early Management of Acute Ischemic Stroke, Stroke. 2019;50(12):e344-e418 (DOI 10.1161/STR.0000000000000211)
- FDA — Activase (alteplase) Prescribing Information (DailyMed)
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.