October 18, 2025

By Warren Howard | in Medications | 1 Comments

Verapamil Dosing Calculator for Children

Calculate Safe Verapamil Dose for Children

Input child's weight and age to determine appropriate dosing range for verapamil

Quick Takeaways

  • Verapamil is the only calcium channel blocker widely approved for specific pediatric heart rhythm issues.
  • Dosing is weight‑based and requires careful titration in infants and toddlers.
  • Common side effects include constipation, low blood pressure, and slowed heart rate.
  • Contraindications are severe heart block, heart failure, and certain congenital heart defects.
  • When used correctly, verapamil can prevent life‑threatening arrhythmias in children.

What is Verapamil?

When treating children, Verapamil is a calcium channel blocker that slows electrical conduction through the heart and relaxes blood vessels. It belongs to the phenylalkylamine class and has been on the market for more than four decades. While adults use it for angina and atrial fibrillation, pediatric use is limited to a few well‑defined rhythm disturbances.

How Verapamil Works in Children

Verapamil blocks L‑type calcium channels in cardiac myocytes. By reducing calcium influx, it slows the depolarization of the atrioventricular (AV) node, which helps terminate or prevent re‑entrant tachyarrhythmias. In the vascular smooth muscle, the same mechanism causes vasodilation and modest blood‑pressure reduction, a useful side effect when a child has concurrent hypertension.

Approved Pediatric Indications

The drug is officially endorsed for:

  • Supraventricular tachycardia (SVT) that does not respond to vagal maneuvers or adenosine.
  • Pre‑excitation syndromes such as Wolff‑Parkinson‑White (WPW) with documented orthodromic tachycardia.
  • Certain cases of pediatric hypertension when other agents are unsuitable.

Off‑label use, such as for hypertensive crisis, is sometimes considered by specialists, but it carries higher risk and demands close monitoring.

Pediatric doctor reviewing Verapamil dosing chart with scale and syringe.

Dosing Guidelines for Different Ages

Dosing is always calculated per kilogram of body weight. Below is a practical chart used by many pediatric cardiology units.

Verapamil Dosing in Children (mg/kg)
Age Group Initial Dose Maintenance Dose Maximum Daily Dose
Neonates (0‑28 days) 0.01‑0.02 0.02‑0.04 0.5
Infants (1‑12 months) 0.02‑0.03 0.04‑0.06 1.0
Children (1‑12 years) 0.03‑0.04 0.06‑0.10 2.0
Adolescents (13‑18 years) 0.04‑0.05 0.10‑0.12 3.0

All doses should be given orally in divided doses every 6‑8 hours. Intravenous administration is reserved for acute SVT termination and must be diluted to a concentration not exceeding 0.1 mg/mL.

Safety Profile & Common Side Effects in Kids

Because children metabolize drugs differently, side‑effects can appear at lower concentrations than in adults. The most frequently reported reactions are:

  • Constipation - up to 20 % of patients, manageable with dietary fiber and occasional laxatives.
  • Bradycardia - heart‑rate drops below age‑appropriate norms in 5‑10 %.
  • Hypotension - especially after rapid IV bolus.
  • Peripheral edema - rare, usually dose‑related.

Severe complications, such as ventricular arrest, are extremely uncommon but have been documented when verapamil is combined with other negative inotropes or in children with undiagnosed heart block.

When to Avoid Verapamil: Contraindications in Pediatrics

Before prescribing, clinicians must screen for the following conditions:

  • Second‑ or third‑degree AV block without a pacemaker.
  • Decompensated heart failure or cardiogenic shock.
  • Significant left‑ventricular outflow tract obstruction (e.g., severe aortic stenosis).
  • Known hypersensitivity to verapamil or its excipients.

If any of these are present, alternative agents such as beta‑blockers or digoxin are preferred.

Parent and child checking medication schedule with pill organizer and prune juice.

Comparing Verapamil with Other Calcium Channel Blockers

Verapamil vs. Diltiazem in Pediatric Use
Characteristic Verapamil Diltiazem
Primary Action Strong AV‑node suppression Moderate AV‑node suppression
Approved Pediatric Indications SVT, WPW, pediatric hypertension Rarely used; off‑label only
Side‑effect Profile Higher constipation, bradycardia Less constipation, more headache
Interaction Risk Strong with beta‑blockers, digoxin Moderate with CYP3A4 inhibitors
Typical Dosing (mg/kg) 0.03‑0.12 0.025‑0.05

Overall, verapamil remains the go‑to calcium channel blocker for pediatric rhythm control because its AV‑node effect is more predictable.

Practical Tips for Parents & Clinicians

  • Always weigh the child before each dose; growth can quickly change the required amount.
  • Start with the lowest effective dose and titrate weekly while monitoring heart‑rate and blood pressure.
  • Encourage a high‑fiber diet to reduce constipation; a glass of prune juice can work wonders.
  • If the child feels unusually tired or dizzy, check the pulse - a rate under 60 bpm in a toddler warrants immediate review.
  • Keep a written medication schedule handy; missed doses can lead to rebound tachycardia.

Both parents and healthcare providers should maintain an open line of communication. In acute SVT episodes, having an action plan (vagal manoeuvres, emergency contact numbers, and a rescue dose of adenosine if prescribed) can save valuable minutes.

Frequently Asked Questions

Can I give my child verapamil for high blood pressure?

Yes, but only under specialist supervision. Pediatric hypertension often requires a combination of lifestyle changes and medication, and verapamil is reserved for cases where other first‑line drugs fail or cause side‑effects.

What should I do if my child experiences a sudden drop in heart rate?

Stop the medication immediately and call your pediatric cardiologist. In an emergency, go to the nearest emergency department - bradycardia can lead to dizziness, fatigue, or worse if not treated promptly.

Is verapamil safe for newborns?

Neonatal use is rare and only considered when the benefit outweighs the risk. Doses are much lower (0.01‑0.02 mg/kg) and require continuous cardiac monitoring.

How does verapamil differ from beta‑blockers in children?

Beta‑blocker primarily reduces heart‑rate by blocking adrenaline receptors, while verapamil blocks calcium influx. Beta‑blockers are more often used for hypertension, whereas verapamil’s strength is controlling AV‑node‑mediated tachycardia.

Can verapamil be used alongside adenosine?

Adenosine is usually the first rescue drug for acute SVT. Verapamil can be given after adenosine fails, but both should not be administered simultaneously because the combined effect can cause profound AV‑node block.