Rectal Acetaminophen Dosing for 3-Month-Old Infant (4.572 kg)
The recommended rectal acetaminophen dose for this 3-month-old infant weighing 4.572 kg is 10-15 mg/kg per dose, which equals approximately 46-69 mg per dose, administered every 4-6 hours as needed, with a maximum daily dose not exceeding 60 mg/kg/day (274 mg/day for this infant). 1
Weight-Based Dosing Calculation
- Standard dosing: 10-15 mg/kg per dose rectally 1
- For this 4.572 kg infant:
- Minimum dose: 46 mg (10 mg/kg × 4.572 kg)
- Maximum dose: 69 mg (15 mg/kg × 4.572 kg)
- Dosing interval: Every 4-6 hours (q4-6h) as needed 1
- Maximum daily dose: 60 mg/kg/day = 274 mg/day for this infant 1
Critical Safety Considerations
- Use the lowest effective dose for the shortest duration necessary, as acetaminophen should only be used when needed with no safer alternative available 2
- Do not exceed 60 mg/kg/day total when combining rectal with any other acetaminophen formulations (oral or IV), as exceeding this threshold significantly increases hepatotoxicity risk 1, 3
- Monitor for clinical improvement within the first few doses for fever or pain control 1
Common Pitfalls to Avoid
- Avoid dosing more frequently than every 4 hours, as this increases risk of unintentional overdose, which accounts for up to half of acetaminophen toxicity cases 3
- Verify total daily acetaminophen exposure from all sources, as unintentional overdoses often occur when caregivers inadvertently combine multiple acetaminophen-containing products 3
- Transition to oral route when feasible, as rectal absorption can be variable and oral administration provides more predictable pharmacokinetics 1
Clinical Context
Acetaminophen remains the safest analgesic and antipyretic for infants when used appropriately, with hepatotoxicity unlikely unless plasma concentrations far exceed therapeutic levels (therapeutic range: 5-20 mcg/mL vs toxic threshold >150 mcg/mL) 4. The key to safe use is strict adherence to weight-based dosing limits and avoiding cumulative overdose from multiple sources 4, 3.