Acetaminophen Dosing for a 19-lb Child
Give 120–130 mg of acetaminophen (Tylenol) every 4–6 hours as needed, not exceeding 5 doses in 24 hours.
Weight-Based Calculation
- A 19-lb child weighs approximately 8.6 kg 1
- The standard acetaminophen dose is 10–15 mg/kg per dose 1, 2, 3
- For this child: 8.6 kg × 10 mg/kg = 86 mg (minimum effective dose) and 8.6 kg × 15 mg/kg = 129 mg (optimal dose) 1
- Use 15 mg/kg (approximately 130 mg) for optimal antipyretic and analgesic effect, as 10 mg/kg doses often fail to reach therapeutic plasma concentrations needed for fever reduction 4, 3
Practical Dosing Guidance
- Oral suspension is strongly preferred over rectal suppositories because it provides more rapid and consistent absorption 1, 5
- Administer every 4–6 hours as needed 1, 2
- Maximum daily dose: 60 mg/kg/day (approximately 520 mg for this child) or 5 doses in 24 hours, whichever is lower 1
Common Pitfalls to Avoid
- Underdosing is extremely common: Studies show 27% of parents give less than 10 mg/kg, resulting in inadequate fever control 6
- Age-based dosing causes errors: Weight-based dosing is more accurate than manufacturer age-based recommendations, which can result in subtherapeutic levels 4
- The 10 mg/kg dose is often insufficient: Pharmacokinetic modeling demonstrates that 10 mg/kg fails to reach the 10–20 μg/mL plasma concentration needed for antipyresis, while 15 mg/kg consistently achieves therapeutic levels 4, 3
Special Considerations for Dose Reduction
If this child has any of the following conditions, reduce the dose to 10 mg/kg (86 mg):
- Chronic malnutrition or fasting >8 hours without adequate caloric intake 1
- Taking cytochrome P450-inducing medications (e.g., isoniazid) 1
- Pre-existing liver disease 1