Acetaminophen and Ibuprofen Dosing for an 18-Month-Old
For an 18-month-old child, administer acetaminophen 10-15 mg/kg per dose every 4-6 hours (maximum 60 mg/kg/day) or ibuprofen 10 mg/kg per dose every 6-8 hours, using oral syrup formulations for optimal absorption. 1
Acetaminophen Dosing
- Standard dose: 10-15 mg/kg per dose, administered every 4-6 hours 1
- Maximum daily dose: 60 mg/kg/day or 5 doses in 24 hours, whichever is lower 1
- Oral syrup is preferred over rectal suppositories because it provides more rapid and consistent absorption 1
- For an average 18-month-old weighing approximately 10-12 kg, this translates to 100-180 mg per dose 1
Important Safety Considerations
- Never exceed the maximum daily dose of 60 mg/kg/day to prevent hepatotoxicity 1
- Rectal acetaminophen should be used cautiously due to erratic absorption, which may result in inadequate analgesia or risk of accumulation with repeated dosing 1
Ibuprofen Dosing
- Standard dose: 10 mg/kg per dose, administered every 6-8 hours 1, 2
- Ibuprofen is appropriate for children 6 months and older 1
- For an 18-month-old weighing 10-12 kg, this translates to 100-120 mg per dose 1
- The longer dosing interval (6-8 hours) compared to acetaminophen (4-6 hours) may be more convenient for caregivers 1
Comparative Efficacy
- At physician-directed doses (acetaminophen 15 mg/kg vs ibuprofen 10 mg/kg), both medications show similar efficacy for pain relief 3, 2
- Ibuprofen demonstrates superior antipyretic effect at 2,4, and 6 hours post-treatment compared to acetaminophen, with effect sizes of 0.31-0.33 at these time points 2
- Both medications have similar safety profiles when used at recommended doses 3, 2
Alternating Medications
- If both medications are needed for persistent fever or pain, stagger dosing every 3-4 hours by giving acetaminophen every 4-6 hours and ibuprofen every 6-8 hours 1
- This approach may provide better symptom control than either medication alone, though it increases complexity and risk of dosing errors 1
Critical Safety Warnings
- Avoid ibuprofen overdose: A case report documented severe toxicity (seizures, metabolic acidosis) in an 18-month-old who ingested 600 mg/kg of ibuprofen 4
- Always use weight-based dosing rather than age-based dosing for accuracy 5, 6
- Use calibrated measuring devices (oral syringes) rather than household spoons to prevent dosing errors 5