tPA Calculator - Free Online Tool

Alteplase and Tenecteplase dose calculator for acute ischemic stroke — for clinical verification only

The tPA Stroke Dosing Calculator is a clinical decision support tool designed to assist healthcare professionals in calculating weight-based alteplase (Activase) and tenecteplase (TNKase) doses for acute ischemic stroke treatment. Tissue plasminogen activator (tPA) thrombolytic therapy is one of the most time-sensitive and high-risk treatments in emergency medicine, making accurate dose calculation critical. Alteplase remains the FDA-approved standard of care for acute ischemic stroke within a 3-hour treatment window, with off-label use supported in the 3-to-4.5-hour window under specific criteria. The dose of 0.9 mg/kg, with a maximum of 90 mg, is strictly weight-based and must never exceed the 90 mg cap regardless of patient weight. Ten percent of the total dose is administered as an intravenous bolus over one minute, and the remaining 90 percent is infused over 60 minutes via an IV pump. Tenecteplase (TNK) has emerged as an alternative to alteplase for acute ischemic stroke, with several randomized trials demonstrating non-inferiority or superiority for certain outcomes. Its key pharmacological advantages include 8 to 10 times greater fibrin specificity than alteplase and a 3 to 6 times longer plasma half-life, enabling simplified single-bolus administration over just 5 seconds. The FDA-approved dose for stroke is 0.25 mg/kg with a maximum of 25 mg from a single IV bolus. Proper patient eligibility must be confirmed before administering either thrombolytic. Blood pressure must be controlled below 185/110 mmHg before treatment begins, blood glucose must be above 50 mg/dL, and coagulation parameters must be within acceptable ranges. A non-contrast CT of the head must exclude intracranial hemorrhage and other stroke mimics before treatment initiation. The treatment window is the most time-critical factor. The American Heart Association and American Stroke Association recommend a door-to-needle time of less than 60 minutes, with a target median of 30 minutes or less for optimal outcomes. Every minute of delay in treatment results in the loss of approximately 1.9 million neurons, 14 billion synapses, and 12 km of myelinated nerve fibers. This devastating rate of neuronal loss underscores the phrase 'time is brain' and the urgency of accurate, rapid dose preparation. Post-administration monitoring is equally critical. Blood pressure and neurological status must be checked every 15 minutes for the first 2 hours, every 30 minutes from hours 2 to 8, and hourly from hours 8 to 24. The blood pressure target post-infusion is 180/105 mmHg or below for the first 24 hours. All antithrombotic agents, including aspirin, clopidogrel, heparin, and anticoagulants, must be held for at least 24 hours after tPA administration. A follow-up head CT or MRI at 24 hours is required before resuming antithrombotics. A critical safety note that every clinician must know: the myocardial infarction dosing protocol for alteplase uses a fixed 100 mg dose, which is fundamentally different from the stroke protocol. Using the MI dose for stroke has caused catastrophic hemorrhagic transformation and patient deaths. This calculator is designed exclusively for acute ischemic stroke dosing and will never display doses above the stroke maximum caps. Absolute contraindications to tPA in stroke include intracranial hemorrhage on CT imaging, active internal bleeding, blood pressure that cannot be controlled below 185/110 mmHg despite antihypertensive treatment, DOAC use within the past 48 hours, warfarin use with INR above 1.7, platelet count below 100,000 per microliter, prior intracranial hemorrhage, known intracranial neoplasm or arteriovenous malformation, head trauma or prior stroke within the past 3 months, and symptoms suggesting subarachnoid hemorrhage. Our calculator provides side-by-side alteplase and tenecteplase dose comparisons, a complete administration checklist, post-administration monitoring schedule, dose breakdown charts, and copy-to-clipboard summary for documentation — all fully client-side for maximum privacy and speed in emergency situations.

Understanding tPA Stroke Dosing

Thrombolytic therapy with tPA dissolves the clot causing ischemic stroke by activating plasminogen to plasmin. Accurate weight-based dosing within strict time windows is essential for efficacy and safety.

Alteplase Dosing Protocol

Alteplase (Activase, tPA) is dosed at 0.9 mg/kg with an absolute maximum of 90 mg regardless of weight. The total dose is divided into two components: a 10% IV bolus administered over exactly 1 minute, and the remaining 90% infused over 60 minutes. The 100 mg vial is reconstituted with 100 mL sterile water to create a 1 mg/mL solution, making dose volumes numerically equal to dose weights. After the vial empties, flush the IV line with normal saline to clear approximately 20 mg retained in the tubing. The stroke protocol must never be confused with the STEMI protocol (100 mg fixed dose), which can cause catastrophic hemorrhage if used for stroke.

Tenecteplase Dosing Protocol

Tenecteplase (TNKase) for acute ischemic stroke is dosed at 0.25 mg/kg with a maximum of 25 mg, administered as a single IV bolus over 5 seconds. The standard vial concentration is 5 mg/mL (25 mg/5 mL or 50 mg/10 mL), so dose volume equals dose weight divided by 5. Its simplified single-bolus protocol and superior fibrin specificity (8–10 times greater than alteplase) make preparation faster, which may benefit door-to-needle times. Tenecteplase is FDA-approved for stroke within 3 hours of symptom onset. Frequent BP monitoring is required during and after administration.

Treatment Windows and Eligibility

Alteplase has strong Level A (should offer) evidence within 0 to 3 hours of symptom onset per NINDS criteria, and Level B (should consider) evidence from 3 to 4.5 hours under ECASS III criteria with additional restrictions: NIHSS score must be 25 or below, age must be 80 or under, no combined history of both prior stroke and diabetes, and no oral anticoagulant use. Tenecteplase is FDA-approved within 3 hours. Blood pressure must be below 185/110 mmHg before treatment. Blood glucose must exceed 50 mg/dL. A non-contrast head CT must exclude hemorrhage.

Post-Administration Care

After tPA infusion, intensive monitoring is mandatory: neurological status and blood pressure every 15 minutes for 2 hours, every 30 minutes from hours 2 to 8, and hourly from hours 8 to 24. Target blood pressure below 180/105 mmHg for 24 hours. Hold all antithrombotics (aspirin, clopidogrel, heparin, anticoagulants) for at least 24 hours. Repeat head CT or MRI at 24 hours before resuming any antithrombotics. Watch for signs of symptomatic intracranial hemorrhage: sudden neurological deterioration, new headache, nausea, vomiting, or acute hypertension.

tPA Dosing Formulas

Alteplase Total Dose

Total Dose = 0.9 mg/kg (max 90 mg)

The FDA-approved weight-based dose for alteplase in acute ischemic stroke. The 0.9 mg/kg dose is capped at an absolute maximum of 90 mg regardless of patient weight. Patients weighing 100 kg or more receive the maximum 90 mg dose.

Alteplase Bolus and Infusion Split

Bolus = 10% of Total Dose (over 1 min); Infusion = 90% of Total Dose (over 60 min)

The total alteplase dose is divided into two components: a 10% IV bolus administered over exactly 1 minute for rapid initial thrombolysis, and the remaining 90% infused over 60 minutes via an IV pump for sustained clot dissolution.

Tenecteplase Dose

Total Dose = 0.25 mg/kg (max 25 mg), single IV bolus over 5 seconds

The FDA-approved tenecteplase dose for acute ischemic stroke. A single-bolus administration over 5 seconds simplifies preparation compared to alteplase. The 25 mg maximum applies to patients weighing 100 kg or more.

Weight Conversion (lbs to kg)

Weight (kg) = Weight (lbs) ÷ 2.205

Converts patient weight from pounds to kilograms for dose calculation. Accurate weight is critical — even small errors in weight-based dosing can increase hemorrhage risk or reduce thrombolytic efficacy.

tPA Dosing Reference Tables

Alteplase Dosing by Patient Weight

Pre-calculated alteplase doses for acute ischemic stroke at common patient weights, showing total dose, 10% bolus, 90% infusion, and infusion rate at 1 mg/mL concentration.

Weight (kg)	Total Dose (mg)	Bolus 10% (mg)	Infusion 90% (mg)	Infusion Rate (mL/hr)	Dose Capped?
50	45.0	4.5	40.5	40.5	No
60	54.0	5.4	48.6	48.6	No
70	63.0	6.3	56.7	56.7	No
75	67.5	6.8	60.8	60.8	No
80	72.0	7.2	64.8	64.8	No
85	76.5	7.7	68.9	68.9	No
90	81.0	8.1	72.9	72.9	No
95	85.5	8.6	77.0	77.0	No
100	90.0	9.0	81.0	81.0	Yes (max 90 mg)
110	90.0	9.0	81.0	81.0	Yes (max 90 mg)
120	90.0	9.0	81.0	81.0	Yes (max 90 mg)

tPA Contraindications Checklist

Absolute and relative contraindications to thrombolytic therapy in acute ischemic stroke. All absolute contraindications must be excluded before administration.

Category	Contraindication	Type	Action
Imaging	Intracranial hemorrhage on CT	Absolute	Do NOT administer tPA
Bleeding	Active internal bleeding	Absolute	Do NOT administer tPA
Blood Pressure	BP >185/110 mmHg unresponsive to treatment	Absolute	Treat BP first; reassess
Medications	DOAC use within 48 hours	Absolute	Do NOT administer tPA
Medications	Warfarin with INR >1.7	Absolute	Do NOT administer tPA
Labs	Platelet count <100,000/μL	Absolute	Do NOT administer tPA
History	Prior intracranial hemorrhage	Absolute	Do NOT administer tPA
History	Head trauma or stroke within 3 months	Absolute	Do NOT administer tPA
Presentation	Symptoms suggesting SAH	Absolute	Do NOT administer tPA
Presentation	Minor or rapidly improving symptoms	Relative	Weigh risks vs benefits
History	Major surgery within 14 days	Relative	Weigh risks vs benefits
History	GI/urinary hemorrhage within 21 days	Relative	Weigh risks vs benefits

tPA Dosing Worked Examples

Standard Alteplase Dosing for 75 kg Patient

A 62-year-old patient presents with acute ischemic stroke confirmed by CT. Weight is 75 kg. Time since symptom onset is 1 hour 45 minutes. All eligibility criteria are met.

Calculate total alteplase dose: 0.9 mg/kg × 75 kg = 67.5 mg. This is below the 90 mg cap, so no cap is applied.

Calculate bolus dose (10%): 67.5 × 0.10 = 6.75 mg. Administer over 1 minute IV push.

Calculate infusion dose (90%): 67.5 × 0.90 = 60.75 mg. Infuse over 60 minutes.

Determine infusion rate: At 1 mg/mL concentration (100 mg vial + 100 mL sterile water), rate = 60.75 mL/hr.

Calculate waste: 100 mg vial − 67.5 mg used = 32.5 mg (32.5 mL) to discard.

Assess treatment window: 1 hour 45 minutes is within the standard 0–3 hour window. Proceed per institutional stroke protocol.

Alteplase total dose = 67.5 mg. Bolus = 6.75 mg IV over 1 min. Infusion = 60.75 mg at 60.75 mL/hr over 60 min. Waste = 32.5 mL. Patient is within the standard treatment window. Begin post-infusion BP and neuro monitoring every 15 minutes.

Alteplase Dosing with 90 mg Cap Applied

A 48-year-old patient weighing 110 kg (242 lbs) presents with acute ischemic stroke 2 hours after symptom onset.

Calculate weight-based dose: 0.9 mg/kg × 110 kg = 99 mg. This exceeds the 90 mg maximum.

Apply dose cap: Total dose = 90 mg (maximum, regardless of weight).

Calculate bolus (10%): 90 × 0.10 = 9.0 mg over 1 minute.

Calculate infusion (90%): 90 × 0.90 = 81.0 mg over 60 minutes.

Determine infusion rate: 81.0 mL/hr at 1 mg/mL concentration.

Calculate waste: 100 mg vial − 90 mg used = 10 mg (10 mL) to discard.

Alteplase total dose = 90 mg (CAPPED from 99 mg). Bolus = 9.0 mg IV over 1 min. Infusion = 81.0 mg at 81.0 mL/hr over 60 min. Waste = 10 mL. The 90 mg cap protects heavier patients from increased hemorrhage risk.

Tenecteplase Dosing for Comparison

The same 75 kg patient from Example 1 is being evaluated for tenecteplase as an alternative to alteplase.

Calculate tenecteplase dose: 0.25 mg/kg × 75 kg = 18.75 mg. Below the 25 mg cap.

Calculate dose volume: At 5 mg/mL concentration, volume = 18.75 / 5 = 3.75 mL.

Administration: Single IV bolus over 5 seconds (no infusion required).

Calculate waste: 25 mg vial contains 5 mL. Used 3.75 mL. Waste = 1.25 mL.

Compare to alteplase: Alteplase = 67.5 mg (bolus + 60 min infusion). Tenecteplase = 18.75 mg (single 5-second bolus). Tenecteplase offers faster, simpler administration.

Tenecteplase dose = 18.75 mg in 3.75 mL, single IV bolus over 5 seconds. Compared to alteplase, tenecteplase requires no infusion pump, no 60-minute monitoring of infusion rate, and achieves 8–10x greater fibrin specificity. Both require the same post-administration monitoring schedule.

How to Use the tPA Stroke Dosing Calculator

Select Thrombolytic Agent and Enter Patient Weight

Choose alteplase (tPA), tenecteplase (TNK), or both for side-by-side comparison. Enter the patient weight in kg or lbs. The calculator automatically converts lbs to kg and applies the weight-based formula with the appropriate dose cap (90 mg for alteplase, 25 mg for tenecteplase).

Enter Time Since Symptom Onset

Enter the hours and minutes since the patient's last known well or symptom onset. The calculator displays a color-coded treatment window indicator: standard window (0–3 hours), extended window (3–4.5 hours, alteplase with ECASS III criteria only), or outside standard window (greater than 4.5 hours). This guides eligibility assessment.

Review Doses and Administration Parameters

Review the calculated total dose, bolus dose and volume, infusion dose and rate (for alteplase), or single bolus volume (for tenecteplase), and waste discard volume. All volumes are based on standard reconstitution concentrations (1 mg/mL for alteplase, 5 mg/mL for tenecteplase). Verify independently before administration.

Use Post-Administration Monitoring Schedule and Copy Summary

After dose calculation, review the post-administration BP and neurological monitoring schedule, the antithrombotic hold guidance, and the follow-up CT timing. Use the Copy Summary button to generate a text summary of all dosing parameters for documentation in the patient chart or handoff communication.

Frequently Asked Questions

What is the correct alteplase dose for acute ischemic stroke?

The FDA-approved alteplase dose for acute ischemic stroke is 0.9 mg/kg with an absolute maximum of 90 mg, regardless of patient weight. Ten percent of the total dose (0.09 mg/kg) is given as an IV bolus over exactly 1 minute, and the remaining 90% (0.81 mg/kg) is infused over 60 minutes via an IV pump. The drug is reconstituted in a 100 mg vial with 100 mL of sterile water to produce a 1 mg/mL solution, so dose in milligrams equals dose volume in milliliters. Never use the STEMI alteplase protocol (100 mg fixed dose) for stroke — this error has caused fatal hemorrhagic transformations. Always cap at 90 mg and verify the calculation with a second clinician.

How does tenecteplase dosing differ from alteplase for stroke?

Tenecteplase (TNK) for acute ischemic stroke is dosed at 0.25 mg/kg with a maximum of 25 mg, compared to alteplase at 0.9 mg/kg with a maximum of 90 mg. The key practical difference is administration: tenecteplase is given as a single IV bolus over just 5 seconds, while alteplase requires a 1-minute bolus followed by a 60-minute infusion. Tenecteplase's simplified protocol may reduce preparation time and potential for administration errors. It has 8 to 10 times greater fibrin specificity than alteplase. The standard vial concentration for tenecteplase is 5 mg/mL, so the dose volume in mL equals the dose in mg divided by 5. Tenecteplase is FDA-approved for stroke within 3 hours of symptom onset.

What are the absolute contraindications to tPA in stroke?

Absolute contraindications mean tPA must NOT be administered and include: intracranial hemorrhage visible on CT, active internal bleeding, blood pressure persistently above 185/110 mmHg despite antihypertensive treatment, DOAC use within the past 48 hours, warfarin use with INR above 1.7 or PT above 15 seconds, platelet count below 100,000 per microliter, prior history of intracranial hemorrhage, known intracranial neoplasm or arteriovenous malformation or aneurysm, head trauma or prior ischemic stroke within the past 3 months, and clinical presentation suggesting subarachnoid hemorrhage even if CT is negative. These contraindications apply to all treatment windows and both alteplase and tenecteplase.

What is the 3 to 4.5 hour extended treatment window for alteplase?

The extended treatment window from 3 to 4.5 hours after symptom onset applies only to alteplase, not tenecteplase, and is considered off-label (supported by ECASS III trial evidence). For patients in this window, all of the following criteria must be met: NIHSS score must be 25 or below, the patient must be age 80 or under, there must be no combined history of both prior stroke and diabetes mellitus, no oral anticoagulant use regardless of INR, and imaging must not show involvement of more than one-third of the middle cerebral artery territory. The evidence level is Class IIa under AHA/ASA guidelines. Patients meeting these criteria may benefit significantly from treatment, and the risk of withholding treatment should be weighed carefully against hemorrhage risk.

What monitoring is required after tPA administration?

Post-tPA monitoring is intensive and must continue for 24 hours. Blood pressure and neurological status are assessed every 15 minutes for the first 2 hours, every 30 minutes from hours 2 to 8, and hourly from hours 8 to 24. The blood pressure target is 180/105 mmHg or below for the first 24 hours. All antithrombotics, including aspirin, clopidogrel, heparin, and anticoagulants, must be held for at least 24 hours. A follow-up head CT or MRI must be obtained at 24 hours before any antithrombotic can be resumed. Watch closely for symptomatic intracranial hemorrhage: sudden neurological deterioration, new severe headache, nausea, vomiting, or acute hypertension are warning signs requiring immediate head CT and neurosurgical consultation.

Why is weight-based dosing so important for tPA in stroke?

Weight-based dosing ensures patients receive a therapeutically effective dose while minimizing hemorrhage risk. The alteplase dose of 0.9 mg/kg was established through clinical trials that balanced thrombolytic efficacy against the risk of symptomatic intracranial hemorrhage, which occurs in approximately 6% of treated patients. Overdosing — even by a small margin — significantly increases hemorrhage risk, while underdosing may reduce clot lysis effectiveness. The 90 mg cap protects heavier patients from receiving a potentially dangerous total dose. For this reason, accurate patient weight is essential, and estimated weights should only be used if measured weight is unavailable. Some institutions use lean body weight for very obese patients, though the standard protocol uses total body weight. Always follow your institutional protocol for weight estimation in emergency scenarios.