How to Calculate Pediatric Dosage

What is Pediatric Dosage?

Paediatric drug dosing is weight-based (mg/kg). Children's absorption, distribution, and metabolism differ significantly from adults. Always confirm with a prescriber.

Formula

Clark's rule: Child dose = (Weight in lbs / 150) × Adult dose; Young's rule: (Age / Age+12) × Adult dose; mg/kg dosing preferred (dose = Weight kg × mg/kg)

ChildWeight: Child body weight (kg)
DosePerKg: Dose per kilogram (mg/kg (varies by drug))
ChildDose: Total pediatric dose (mg (or mL if liquid))

Step-by-Step Guide

1Dose (mg) = Weight (kg) × Dose rate (mg/kg)
2Maximum doses apply regardless of weight
3Frequency based on drug half-life
4Age and organ function also affect safe dosing

Worked Examples

Input

Paracetamol 15mg/kg, child 22 kg

Result

Dose = 330mg; every 4–6h; max 4 doses/day

Frequently Asked Questions

Why are pediatric doses different?

Children metabolize drugs differently (slower kidney/liver function in infants). Surface area scaling matters. Proportionally higher drug effect possible (toxicity risk). Always use weight-based dosing.

Should I use Clark's rule or weight-based?

Weight-based (mg/kg) standard now. Clark's rule (weight-based) or Young's rule (age-based) historical. Age-based less accurate. Check pediatric references or pharmacist.

What if dose seems too small?

Verify drug, weight, and reference source. Underdosing common mistake. Double-check with pharmacist before giving. Overdosing = toxicity; underdosing = treatment failure.

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