What is the recommended acetaminophen dose in mg per kilogram for a healthy infant aged 1–3 months?

Acetaminophen Dosing for Infants 1-3 Months of Age

For healthy infants aged 1-3 months, acetaminophen should be dosed at 10-15 mg/kg per dose, administered every 4-6 hours, with a maximum of 60-65 mg/kg/day. 1, 2, 3

Weight-Based Dosing Regimen

• Single dose: 10-15 mg/kg administered orally or rectally 1, 2
• Dosing interval: Every 4-6 hours (not to exceed 4 doses in 24 hours) 1, 4
• Maximum daily dose: 60-65 mg/kg/day for infants 1-3 months of age 3

The 15 mg/kg dose provides more consistent antipyretic effect than 10 mg/kg, maintaining temperature reduction for approximately 6 hours 5. A dose of 10 mg/kg may be insufficient for sustained fever control, while 5 mg/kg has minimal antipyretic effect 5.

Age-Specific Considerations

This age group requires lower total daily doses than older children. While children over 4 months can safely receive up to 90 mg/kg/day, infants 1-3 months should not exceed 60-65 mg/kg/day due to prolonged elimination half-lives and immature hepatic metabolism 3. The elimination half-life in young infants ranges from 1-3.5 hours but can be significantly prolonged compared to older children 5.

Route of Administration

• Oral suspension is preferred over rectal suppositories when possible, as it provides more consistent absorption and predictable response 5
• For injectable paracetamol (IV), the dose is 7.5 mg/kg per dose using a 10 mg/mL solution 6

Critical Safety Parameters

Do NOT exceed 95 mg/kg/day in this age group, as cumulative doses above this threshold carry risk of hepatotoxicity 3. Single ingestions exceeding ten times the recommended dose (>150 mg/kg) are potentially hepatotoxic 1. Chronic overdosing at exposures greater than 140 mg/kg/day for several days carries serious toxicity risk 1.

Common Prescribing Errors to Avoid

• 17% of prescriptions exceed safe dosing limits in clinical practice, though most are caught by pharmacy review 3
• Many practitioners are uncertain about safe dosing in infants under 3 months, leading to either underdosing or potentially dangerous overdosing 3
• Always calculate the total 24-hour dose to ensure it remains below 65 mg/kg/day 3

Practical Dosing Example

For a 5 kg infant (typical 2-month-old):

• Single dose: 50-75 mg (10-15 mg/kg)
• Maximum daily dose: 300-325 mg (60-65 mg/kg/day)
• Dosing schedule: 60 mg every 6 hours (total 240 mg/day) would be safe and effective 2, 3