Acetaminophen Dosing in Children
For children, 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 dosing whenever possible to ensure therapeutic efficacy and safety.
Weight-Based Dosing (Preferred Method)
The standard dose is 10-15 mg/kg per dose, administered every 4-6 hours as needed 1. This weight-based approach is critical because:
- 10 mg/kg doses may be subtherapeutic, failing to reach the plasma concentration (10-20 μg/mL) required for antipyresis 2
- 15 mg/kg per dose is more reliably effective, achieving adequate plasma concentrations across different weight ranges 2, 3
- A loading dose of 25 mg/kg followed by 12.5 mg/kg every 6 hours has been proposed as an alternative regimen 3
Maximum Daily Limits
The maximum daily dose should not exceed 75-90 mg/kg/day to prevent cumulative hepatotoxicity 4. Specifically:
- Children and adolescents: Maximum 75 mg/kg/day (or 4000 mg/day, whichever is less)
- Avoid exceeding 90-95 mg/kg/day under any circumstances, as this threshold is associated with hepatic and renal toxicity risk 4
Dosing Interval
Administer doses every 4-6 hours as needed, with 4-hour intervals being standard based on the drug's half-life of 1-3.5 hours 1, 3. Do not exceed 5 doses in 24 hours.
Age-Based Approximations (When Weight Unknown)
While weight-based dosing is superior, age-based schedules can be used when weight is unavailable 1:
- Ages 2-3 years (10.9-15.9 kg): The manufacturer's 160 mg dose is only adequate for children at the lower end of this weight range (10.9 kg), but subtherapeutic for heavier children in this age group 2
- This highlights why age-based dosing is problematic: up to 30% of children receive inadequate doses when age-based recommendations are followed 2
Special Populations
Infants 1-3 Months
- Recommended dose: 60-65 mg/kg/day in divided doses, though pharmacokinetic data suggest higher doses may be appropriate 4
- Many practitioners are uncertain about dosing in this age group, leading to inconsistent prescribing 4
Neonates (Under 1 Month)
- Recommended dose: 30 mg/kg/day achieves therapeutic concentrations 4
- No established dosing guidelines exist for neonates under 2 weeks of age; further studies are needed 4
- Use with extreme caution and consider consultation
Route of Administration
Oral suspension is preferred over suppositories when possible, as it provides more consistent absorption and response, though both routes at 10-15 mg/kg show similar overall antipyretic effects 3.
Common Pitfalls to Avoid
- Do not rely on age-based dosing charts from manufacturers, as these frequently result in underdosing, particularly in the 2-3 year age range 2
- Do not use 10 mg/kg doses expecting full antipyretic effect; this dose is often subtherapeutic 2, 3
- Monitor cumulative daily doses carefully in hospitalized children, as 17% of prescriptions may exceed safe limits even when individual doses appear appropriate 4
- Verify actual weight rather than estimating to ensure accurate dosing 1, 2