Acetaminophen Dosing for a 5-Month-Old Infant
For a 5-month-old infant weighing 6–7 kg, administer acetaminophen 10–15 mg/kg per dose every 4–6 hours as needed, which translates to 60–105 mg per dose, not exceeding 5 doses in 24 hours. 1
Weight-Based Dosing Algorithm
The American Academy of Pediatrics emphasizes that weight-based dosing is essential for infants rather than age-based dosing to ensure both safety and efficacy 1. For your 5-month-old:
- Minimum dose (10 mg/kg): 60–70 mg per dose 1
- Maximum dose (15 mg/kg): 90–105 mg per dose 1
- Dosing interval: Every 4–6 hours as needed 1
- Maximum daily limit: Do not exceed 75 mg/kg/day (450–525 mg/day for a 6–7 kg infant) 1
Practical Dosing Considerations
The 15 mg/kg dose is more effective than 10 mg/kg for achieving adequate antipyresis. Research demonstrates that 10 mg/kg often fails to reach therapeutic plasma concentrations (10–20 μg/mL) needed for fever reduction, while 15 mg/kg consistently achieves this target 2. A dose-response relationship clearly shows that 20 mg/kg single doses are more effective than 10 mg/kg, and 5 mg/kg has minimal antipyretic effect 3.
For optimal fever control, aim for the higher end of the dosing range (15 mg/kg) unless there are specific contraindications 4, 2. More than 10 mg/kg is required to maintain temperature reduction of 1.5°C below baseline for 6 hours 3.
Critical Safety Parameters
- Never exceed 5 doses in 24 hours 1
- Maximum daily dose: 75 mg/kg/day or 4000 mg total, whichever is lower 1
- Chronic overdosing (>140 mg/kg/day for several days) carries risk of serious hepatotoxicity 5
- Single ingestions exceeding 10 times the recommended dose are potentially toxic 5
Common Pitfalls to Avoid
Infants under 1 year are at highest risk for dosing errors. Studies show that 62% of parents give inaccurate acetaminophen doses, with infants being 1.4 times more likely to receive incorrect dosing compared to older children 6. The primary error stems from using age-based rather than weight-based dosing 6.
Always use weight-based calculations rather than manufacturer's age-based recommendations on packaging, as these frequently result in underdosing or overdosing depending on the infant's actual weight 2, 6. Parents who base dosing on weight are significantly less likely to give inaccurate doses (RR 0.71) 6.
Formulation Selection
Oral suspension is preferred over rectal suppositories for infants, as it provides more consistent absorption and predictable response, though both routes show similar overall efficacy at equivalent doses 3.