Acetaminophen Dosing for a 5-Year-Old Weighing 90 lbs
For a 5-year-old child weighing 90 lbs (approximately 41 kg), give 410–615 mg of acetaminophen per dose every 4–6 hours, not exceeding 2,460 mg in 24 hours (5 doses maximum). 1
Weight-Based Calculation
- The child weighs 90 lbs, which converts to approximately 41 kg (90 ÷ 2.2 = 40.9 kg).
- The American Academy of Pediatrics recommends 10–15 mg/kg per dose every 4–6 hours. 1
- This yields a dose range of 410 mg (10 mg/kg × 41 kg) to 615 mg (15 mg/kg × 41 kg) per dose. 1
- The maximum daily dose is 60 mg/kg per day, which equals 2,460 mg/day for this child (60 mg/kg × 41 kg). 1
- Never exceed 5 doses in 24 hours to prevent hepatotoxicity. 1
Practical Dosing Recommendations
- Use 500 mg per dose as a practical middle-ground option (approximately 12 mg/kg), which is safe, effective, and easy to measure with standard formulations. 1, 2
- Alternatively, 600 mg per dose can be used if higher analgesia or antipyresis is needed, staying within the 15 mg/kg upper limit. 1
- Administer doses every 4–6 hours as needed, spacing them appropriately to avoid exceeding the daily maximum. 1
Important Caveats for This Weight
- This child is significantly above the typical weight for a 5-year-old (normal range is approximately 16–21 kg). 1
- Children weighing more than 40 kg may approach adult dosing thresholds, but pediatric weight-based dosing (10–15 mg/kg) should still be used rather than defaulting to adult fixed doses. 1
- The oral syrup formulation is absorbed more rapidly and provides more consistent response compared to suppositories, so prefer liquid or chewable tablets if the child can tolerate them. 1
Risk Factors That Require Dose Reduction
If any of the following apply, reduce the dose to 10 mg/kg (410 mg) per dose rather than using the higher end of the range: 1
- Chronic malnutrition or fasting for more than 8 hours without adequate caloric intake (increases hepatotoxicity risk). 1
- Medications that induce cytochrome P450 enzymes (e.g., isoniazid), which increase production of the toxic NAPQI metabolite. 1
- Pre-existing liver disease, though acetaminophen remains safer than NSAIDs in this population. 1
Common Pitfalls to Avoid
- Underdosing is common: Studies show 27% of parents give less than 10 mg/kg, resulting in inadequate fever or pain control. 3
- Overdosing also occurs: 12% of parents give 20 mg/kg or more per dose, and 17% of hospital prescriptions exceed safe daily limits. 3, 4
- Do not exceed 60 mg/kg/day or 5 doses in 24 hours under any circumstances to prevent cumulative hepatotoxicity. 1
- Avoid confusion from brand-specific labeling: Some manufacturers have voluntarily reduced maximum daily doses on their labels (e.g., 3,000 mg for 500 mg tablets), but this does not change the weight-based pediatric dosing standard of 60 mg/kg/day. 5