What is the tPA (Alteplase) Dosage Calculator?

The tPA (Alteplase) Dosage Calculator calculates intravenous tissue plasminogen activator (IV rt-PA) dosing for adult patients suffering from acute ischemic stroke. In acute stroke protocol according to the American Heart Association / American Stroke Association (AHA/ASA) guidelines, timely administration of alteplase within 3 to 4.5 hours of symptom onset restores cerebral perfusion and significantly improves functional outcomes.

For evaluating patient stroke severity and cardiac emergency profiles, check out our companion clinical tools: the NIH Stroke Scale Calculator and TIMI STEMI Score Calculator.

Standard tPA Dosing Formula for Acute Stroke

The guideline-recommended regimen for intravenous alteplase in acute ischemic stroke consists of:

Total Weight-Based Dose: 0.9 mg per kg of actual body weight.
Maximum Total Dose Ceiling: 90 mg (achieved at 100 kg or greater).
Initial IV Bolus (10%): 0.09 mg/kg (or 10% of total dose) administered intravenously over 1 minute.
Continuous IV Infusion (90%): 0.81 mg/kg (or 90% of total dose) infused continuously over 60 minutes.
Standard Concentration: 1 mg/mL after reconstituting 100 mg powder with 100 mL sterile water for injection.

Step-by-Step Dosing Example

Consider a patient weighing 80 kg:

Total Dose: 80 kg × 0.9 mg/kg = 72.0 mg (72.0 mL).
10% Bolus: 72.0 mg × 0.10 = 7.2 mg (7.2 mL) pushed over 1 minute.
90% Infusion: 72.0 mg × 0.90 = 64.8 mg (64.8 mL) infused over 60 minutes.
Infusion Pump Rate: 64.8 mL / hour.
Vial Waste: 100 mg − 72 mg = 28.0 mg (28.0 mL) discarded prior to administration.

Critical Pre-Administration Checks and Contraindications

Before initiating alteplase therapy, the clinical team must verify:

Time Window: Symptom onset must be within 3.0 to 4.5 hours (or last known normal).
Non-Contrast Head CT: Must rule out intracranial hemorrhage, subarachnoid hemorrhage, or extensive irreversible infarction.
Blood Pressure Control: Systolic BP must be < 185 mmHg and diastolic BP < 110 mmHg. Antihypertensives (such as IV labetalol or nicardipine) should be given if needed before starting tPA.
Blood Glucose: Must be > 50 mg/dL (2.8 mmol/L) to exclude hypoglycemia mimicking focal deficits.
Coagulation Parameters: INR ≤ 1.7, platelets ≥ 100,000/mm³, and no therapeutic doses of direct oral anticoagulants (DOACs) or heparin in the preceding 24 to 48 hours.

Frequently Asked Questions

Why is there a maximum dose cap of 90 mg?

Clinical trials (including the NINDS rt-PA Stroke Study) demonstrated that doses above 90 mg significantly increase the risk of symptomatic intracerebral hemorrhage (sICH) without providing additional recanalization benefit. Therefore, patients weighing 100 kg or more always receive exactly 90 mg.

Why should excess medication be discarded from the vial before starting?

Discarding the excess tPA volume directly from the 100 mg vial before spiking the infusion bag prevents accidental infusion of the entire vial if the infusion pump fails or runs to completion, guarding against catastrophic drug overdose.

How should blood pressure be monitored during and after tPA infusion?

Blood pressure must be maintained below 180/105 mmHg during and for 24 hours following alteplase. Vital signs and neuro checks are performed every 15 minutes for 2 hours, then every 30 minutes for 6 hours, and every 60 minutes until 24 hours post-treatment.

What should be done if neurologic worsening or severe headache occurs during infusion?

Immediately discontinue the tPA infusion, assess vital signs, notify the physician, and order an emergent non-contrast head CT scan to evaluate for symptomatic intracranial hemorrhage.

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tPA Calculator