Injectable Paracetamol Dosing in Children
Critical Clarification: Intramuscular Route Not Recommended
Injectable paracetamol (acetaminophen) is administered intravenously (IV), not intramuscularly (IM), in pediatric practice. The IM route is not standard for paracetamol administration and is not supported by current guidelines or evidence.
IV Paracetamol Dosing by Weight
Standard Dosing Regimen
For children requiring IV paracetamol, dose based on body weight as follows:
- Neonates and infants <10 kg: 7.5 mg/kg per dose every 6 hours 1, 2
- Children 10-33 kg: 15 mg/kg per dose every 6 hours 1, 2
- Children 33-50 kg: 15 mg/kg per dose every 4-6 hours 1, 2
- Children >50 kg and adolescents: 1000 mg per dose every 6 hours 1, 2
Maximum Daily Doses
Critical safety limits to prevent hepatotoxicity:
- Standard maximum: 75 mg/kg/day (not to exceed 4000 mg/day in adolescents) 3, 4
- Historical maximum of 90 mg/kg/day is no longer recommended due to risk of hepatocellular necrosis and renal tubular necrosis 3, 4
- Doses as low as 75 mg/kg/day over 24 hours can cause adverse effects in some children 3
Dilution and Administration
IV Preparation
Paracetamol for IV use comes as a ready-to-use solution (10 mg/mL) and does not require dilution for standard administration. However, if dilution is needed for smaller volumes in neonates:
- Can be diluted in 0.9% normal saline (NS) or 5% dextrose (D5W) 5
- Standard concentration: 10 mg/mL in commercial preparations
- Infusion time: Administer over 15 minutes 1, 2
Volume Calculations
For a 10 mg/mL solution:
- 10 mg paracetamol = 1 mL of solution
- 15 mg/kg dose for a 20 kg child = 300 mg = 30 mL
- 7.5 mg/kg dose for a 5 kg infant = 37.5 mg = 3.75 mL
Special Considerations for Overweight/Obese Children
Use ideal body weight (IBW) rather than actual body weight for dosing calculations in overweight or obese children to prevent inadvertent overdosing and hepatotoxicity 3. Base IBW on the 50th centile of age and gender-specific growth charts 3.
Critical Safety Warnings
- Document weight on every prescription - height documentation helps identify overweight children requiring IBW-based dosing 3
- Review IV paracetamol at 48 hours for potential switch to oral route to avoid unnecessary IV use 3
- Monitor cumulative daily doses carefully - prescriptions exceeding 75 mg/kg/day pose serious toxicity risk 3, 4
- Neonates under 1 month: Use 30-60 mg/kg/day with extreme caution; pharmacokinetic data is limited 4, 6