Acetaminophen Dosing in Children
Acetaminophen should be dosed at 10-15 mg/kg per dose every 4-6 hours in children, with a maximum daily dose of 75 mg/kg/day (not to exceed 4000 mg/day in adolescents), and children weighing more than 40 kg should receive adult dosing. 1, 2
Weight-Based Dosing (Preferred Method)
The most accurate and effective approach is weight-based dosing at 10-15 mg/kg per dose. 2, 3
- Single dose range: 10-15 mg/kg 2, 4, 3
- Dosing interval: Every 4-6 hours as needed 2, 4
- Do not exceed 5 doses in 24 hours 2, 3
Key Evidence Supporting This Approach
- Pharmacokinetic modeling demonstrates that 10 mg/kg doses may not consistently achieve therapeutic plasma concentrations (10-20 μg/mL) needed for antipyresis, particularly in children at the higher end of weight ranges 5
- 15 mg/kg dosing is more reliably effective for achieving therapeutic plasma levels and antipyretic efficacy 5, 3
- Clinical trials involving over 2,300 children confirm that 10-15 mg/kg produces rapid temperature reduction with maximum effect at approximately 3 hours post-administration 3
Maximum Daily Dose
Maximum daily dose should not exceed 75 mg/kg/day (or 4000 mg/day in adolescents, whichever is less) 2, 3
- This translates to no more than 5 doses per 24-hour period when dosing every 4-6 hours 2
- For adolescents and larger children approaching adult weight, the absolute maximum is 4000 mg/day 6
Age Restrictions and Special Populations
Children weighing more than 40 kg should be dosed using adult dosing schedules 1
- Neonates and young infants: Acetaminophen elimination is slower in neonates, but by early infancy, clearance approximates adult values 4
- The 4-hour dosing interval is appropriate across all pediatric age groups and does not result in drug accumulation 4
Formulation Considerations
Available preparations include liquid suspensions/elixirs, chewable tablets, and regular tablets 1
- Use appropriate measuring devices for liquid formulations to ensure accurate dosing 1
- Syrup formulations may be absorbed somewhat faster in children compared to solid forms 4
Common Pitfalls to Avoid
Age-based dosing leads to significant dosing errors—up to 30% of children receive inadequate doses when parents use age-based rather than weight-based dosing 5
- Manufacturer's fixed-dose recommendations (e.g., 160 mg for ages 2-3 years) are inadequate for many children in that age range, particularly those at the upper weight limit 5
- A 160 mg dose only achieves therapeutic levels in a 10.9 kg child but falls short in a 15.9 kg child 5
- Always calculate dose based on actual weight, not age 2, 5
Clinical Efficacy Timeline
Expect onset of temperature reduction within 1 hour, with maximum effect at approximately 3 hours post-dose 3