Acetaminophen Pediatric Dosing
For children and infants, acetaminophen should be dosed at 10-15 mg/kg per dose every 4-6 hours, with a maximum daily dose of 75 mg/kg/day (not to exceed 4000 mg/day in adolescents), using weight-based rather than age-based calculations to ensure therapeutic plasma concentrations. 1
Weight-Based Dosing Algorithm
Standard dosing for all pediatric patients:
- Single dose: 10-15 mg/kg per dose 1
- Dosing interval: Every 4-6 hours as needed 1
- Maximum daily dose: 75 mg/kg/day (do not exceed 4000 mg/day regardless of weight) 1, 2
The 15 mg/kg dose is preferred over 10 mg/kg because pharmacokinetic modeling demonstrates that 10 mg/kg produces peak plasma concentrations of only 6.38-8.55 μg/mL, which falls below the therapeutic range of 10-20 μg/mL required for effective antipyresis, whereas 15 mg/kg achieves 9.57-12.8 μg/mL 3. A dose-response relationship confirms that 20 mg/kg as a single dose is more effective than 10 mg/kg, while 5 mg/kg has minimal antipyretic effect 4.
Special Considerations for Infants Under 2 Months
Infants under 2 months require medical evaluation before acetaminophen administration because fever in this age group may indicate serious bacterial infection requiring immediate assessment rather than empiric antipyretic therapy 5. When acetaminophen is indicated after medical evaluation, use the same weight-based dosing of 10-15 mg/kg per dose 1.
Critical Dosing Pitfalls
Age-based dosing leads to significant underdosing errors:
- 62% of parents give inaccurate acetaminophen doses when using age-based recommendations 5
- Infants under 1 year are 1.40 times more likely to receive incorrect doses (95% CI 1.06-1.86) 5
- Manufacturer age-based recommendations (such as 160 mg for ages 2-3 years) are only effective for children at the lower weight limit (10.9 kg) and result in subtherapeutic concentrations for heavier children in that age range 3
Parents who base dosing on weight rather than age are significantly less likely to misdose medication (RR 0.71, P < 0.03) 5.
Alternative Loading Dose Regimen
For situations requiring rapid antipyresis, an alternative evidence-based regimen consists of:
This regimen achieves therapeutic plasma concentrations (4-18 mg/L) more rapidly while maintaining safety 4.
Route of Administration
Oral suspension is preferred over rectal suppositories because it produces more consistent therapeutic responses, although both routes achieve similar peak concentrations when dosed at 10-15 mg/kg 4.
Maximum Daily Limits
The maximum daily dose must not exceed: