tPA (Alteplase) Dosing for Ischemic Stroke Calculator

Learn how adult alteplase (tPA) dosing for acute ischemic stroke is calculated: 0.9 mg/kg (max 90 mg), 10% bolus over 1 minute, 90% over 60 minutes, mg-to-mL conversion, monitoring, and safe use of dosing tools.

tPA (Alteplase) Dosing for Acute Ischemic Stroke

Weight-based total dose (0.9 mg/kg, maximum 90 mg) with 10% intravenous bolus over 1 minute and 90% infusion over 60 minutes, consistent with standard adult alteplase labeling for acute ischemic stroke. Confirm reconstitution and final concentration with your product insert before drawing volume.

Body weight

Prepared concentration (for volume)

Choose the concentration of your diluted alteplase per pharmacy protocol and package insert.

Disclaimer: This tool is for educational support only. It does not verify eligibility for thrombolysis, substitute for the official prescribing information, or replace institutional protocols and clinician judgment.

Alteplase (tPA) for acute ischemic stroke (adults)

For eligible adults with acute ischemic stroke, the widely referenced regimen is 0.9 mg/kg total intravenous dose, not to exceed 90 mg. Of the total dose, 10% is given as an initial intravenous bolus over approximately 1 minute, and the remaining 90% is infused intravenously over 60 minutes. Treat as early as possible within the labeled time from symptom onset and follow hemodynamic monitoring and antithrombotic restrictions in the full prescribing information.

Volume to withdraw depends on how your pharmacy prepares the solution (e.g. 1 mg/mL or 2 mg/mL after reconstitution and dilution). This calculator uses your selected concentration to convert mg → mL for bolus and infusion portions separately.

Calculation steps

1. Total dose (mg): min(weight kg × 0.9, 90)

2. Bolus (mg): 10% × total — administer IV over ~1 minute

3. Infusion (mg): 90% × total (remainder after bolus) — IV over 60 minutes

4. Volume (mL): dose mg ÷ concentration mg/mL for each portion

Example

Adult weighing 80 kg (preparation at 1 mg/mL):

Total = min(80 × 0.9, 90) = 72 mg

Bolus = 10% × 72 = 7.2 mg → 7.2 mL at 1 mg/mL

Infusion = 72 − 7.2 = 64.8 mg → 64.8 mL at 1 mg/mL over 60 min

What this calculator does not do

• It does not determine inclusion/exclusion criteria, imaging selection, or extended-window eligibility.
• It does not cover alternate indications (e.g. pulmonary embolism, MI) or pediatric stroke dosing.
• Institutional protocols, dual antiplatelet interaction timing, and blood pressure targets must follow current AHA/ASA guidance and local policy.

What alteplase (tPA) is and why dosing matters

Alteplase is a recombinant tissue plasminogen activator that promotes fibrinolysis. In the setting of carefully selected acute ischemic stroke, intravenous thrombolysis aims to restore perfusion in an occluded cerebral artery. The clinical benefit is tightly linked to patient selection, time from symptom onset, blood pressure control, and meticulous dosing. Underdosing may reduce therapeutic effect; incorrect preparation or administration increases operational risk. This article explains the standard adult weight-based regimen reflected in widely used product labeling so clinicians and learners can align calculator output with bedside workflow—always subject to current prescribing information, institutional protocols, and shared decision-making.

Scope: adults with acute ischemic stroke

The dosing pattern described here applies to the adult acute ischemic stroke indication as commonly summarized in educational materials and labeling: a total intravenous dose of 0.9 mg per kilogram of body weight, not to exceed 90 mg. Pediatric stroke management, pulmonary embolism or myocardial infarction indications, and investigational or protocol-specific regimens are not interchangeable with this stroke pathway. If a patient is enrolled in a trial or covered by a hospital-specific guideline that specifies a different mg/kg plan, follow that source—not a generic online calculator.

The labeled dose structure: total, bolus, and infusion

For the adult ischemic stroke pathway, the total dose is derived from actual (or estimated) body weight:

Total dose (mg) = weight (kg) × 0.9, with a hard maximum of 90 mg regardless of weight.
Initial bolus = 10% of the total dose, given intravenously over approximately one minute.
Remaining infusion = the complement of the bolus (effectively 90% of the total when the split is exact), infused intravenously over 60 minutes.

Expressed compactly: after computing the capped total, the bolus is one-tenth of that total; the infusion volume carries the rest so that bolus plus infusion equals the full prescribed total. Pharmacy and nursing checks typically verify both the milligram amounts and the volumes drawn from the prepared solution.

Worked examples at a glance

Weight (kg)	Total (mg)	Bolus 10% (mg)	Infusion remainder (mg)
60	54.0	5.4	48.6
70	63.0	6.3	56.7
80	72.0	7.2	64.8
100	90.0 (cap)	9.0	81.0
120	90.0 (cap)	9.0	81.0

Notice how the 90 mg ceiling dominates for heavier patients: once weight × 0.9 would exceed 90 mg, the total stays fixed at 90 mg and the 10%/remainder split is applied to that capped total.

From milligrams to milliliters

Manufacturers specify how to reconstitute and dilute alteplase. After preparation, the solution has a known concentration in mg/mL (commonly 1 mg/mL in many stroke preparation workflows, though 2 mg/mL may appear in some settings). To obtain draw volumes:

Bolus volume (mL) = bolus dose (mg) ÷ concentration (mg/mL)
Infusion volume (mL) = infusion dose (mg) ÷ concentration (mg/mL)

Always confirm the final concentration on the bag or syringe label prepared by pharmacy. A dosing calculator that offers a concentration toggle is only as accurate as the value you select to match the physical product in front of you.

Weight inputs: kilograms vs pounds

Clinical dosing should be based on a recent, reliable weight. If only pounds are available, convert to kilograms before applying 0.9 mg/kg (for example, pounds × 0.453592). In unstable or bedbound patients, teams sometimes use a best available estimate; document the source and recognize that large errors in weight translate directly into dose error. Very low or very high weight extremes deserve an extra cross-check against the 90 mg cap and institutional policy.

What must be decided before the dose is given

A calculator that outputs milligrams and milliliters does not establish eligibility. Before thrombolysis, the care team integrates:

Time last known well and whether the patient falls within an approved treatment window for IV therapy under your guideline set.
Neuroimaging (typically non-contrast CT or MRI) to exclude hemorrhage and to contextualize early ischemic changes relative to local decision rules.
Blood pressure thresholds and a plan for sustained control before, during, and after infusion.
Anticoagulant and antiplatelet context, recent procedures, bleeding history, and other exclusionary or cautionary factors per labeling and stroke consensus guidance.
Coagulation studies and glucose when indicated, and relevant laboratory screening per protocol.

These elements change over time as evidence and policy evolve; the numeric dose is just one line in a multi-step safety process.

Blood pressure, monitoring, and common post-administration rules

Symptomatic intracranial hemorrhage is among the most feared complications of thrombolysis. While pathophysiology is multifactorial, strict blood pressure management around the bolus and infusion is a recurring theme in stroke pathways. Teams typically monitor neurologic status and vital signs on a structured schedule, with clear escalation paths for sudden headache, vomiting, acute hypertension, or focal worsening. Antithrombotic medications are generally held for a defined interval after alteplase unless a separate evidence-based exception applies; follow your institution’s antithrombotic reconciliation policy.

Communication, double checks, and handoffs

High-consequence medications benefit from closed-loop communication: the ordered total dose, bolus amount, infusion amount, infusion duration, and concentration are stated aloud and verified by two qualified individuals when policy requires. During handoffs, explicitly include whether the bolus has been completed, the infusion rate, and any PRN antihypertensive plan. A printed or Epic-visible dosing worksheet that matches the calculator output reduces transcription error.

Special populations and situations requiring extra scrutiny

Certain scenarios demand caution beyond a simple mg/kg calculation:

Pregnancy and postpartum contexts—multidisciplinary input is typical.
Recent surgery, arterial puncture at non-compressible sites, or active bleeding—often contraindicated or high risk.
Severe hepatic disease, major stroke on imaging, or large established infarct—risk–benefit reassessment.
Concurrent anticoagulation or novel agents—interpretation may require medication-specific assays or expert consultation per protocol.
Wake-up stroke or unknown onset—advanced imaging selection may apply rather than conventional clocks alone.

None of these nuances are captured by a dosing calculator; they require clinician judgment and local pathways.

How this calculator fits into practice

The CalcMD tool applies the 0.9 mg/kg capped at 90 mg rule, splits the bolus and remainder, and optionally converts to volume at 1 or 2 mg/mL. Use it to teach the arithmetic, to cross-check manual calculations, or to preview draw volumes during simulation. It is not a substitute for the package insert, pharmacist verification, or emergency neurology/stroke team authorization. When any discrepancy arises between the calculator, the electronic order, and the labeled preparation, stop and reconcile before administration.

Documentation reminders

Clear documentation supports medicolegal clarity and quality review: record weight basis, total mg, bolus mg and time, infusion mg and duration, concentration, lot numbers if required, and the clinician responsible for the thrombolysis decision. Note pertinent inclusion/exclusion reasoning at a high level as your charting standard requires.