Weight-Based Dosing for Acetaminophen and Ibuprofen
Acetaminophen (Tylenol) Weight-Based Dosing
For children, acetaminophen should be dosed at 10–15 mg/kg per dose, administered every 4–6 hours, with a maximum daily limit that does not exceed 75 mg/kg/day or 4000 mg/day (whichever is lower). 1
Pediatric Dosing Guidelines
- Single dose range: 10–15 mg/kg every 4–6 hours 1
- Maximum daily dose: 75 mg/kg/day or 4000 mg/day (whichever is lower) 2
- Dosing interval: Every 4–6 hours, not to exceed 5 doses in 24 hours 2
Adult Dosing Guidelines
- Single dose: 650–1000 mg (maximum 1000 mg per dose) 3
- Dosing interval: Every 4–6 hours 2
- Maximum daily dose: 4000 mg/day for healthy adults, though 3000 mg/day is increasingly recommended for chronic use 2
Special Population Adjustments
- Elderly patients (≥60 years): Limit to ≤3000 mg/day for chronic administration 2
- Patients with liver disease or chronic alcohol use: Maximum 2000–3000 mg/day 2, 4
- Infants <1 year: Require particular attention to weight-based dosing, as this age group has the highest risk of dosing errors 5
Critical Dosing Pitfalls to Avoid
- Combination products: Each unit of opioid-acetaminophen combinations should contain ≤325 mg acetaminophen; always account for acetaminophen from ALL sources including over-the-counter cold/flu remedies 2
- Underdosing risk: Many commercially available dosing schedules recommend inadequate amounts; weight-based dosing (10–15 mg/kg) provides more accurate therapeutic levels than age-based approximations 1
- Parental dosing errors: 62% of parents give inaccurate acetaminophen doses, particularly to infants; caregivers who dose by weight are significantly less likely to make errors (RR 0.71) 5
Ibuprofen (Advil) Weight-Based Dosing
For children, ibuprofen should be dosed at 5–10 mg/kg per dose, administered every 6–8 hours, with a maximum daily dose of 40 mg/kg/day or 2400 mg/day (whichever is lower).
Pediatric Dosing Guidelines
- Single dose range: 5–10 mg/kg every 6–8 hours (based on general medical knowledge and standard pediatric practice)
- Maximum daily dose: 40 mg/kg/day or 2400 mg/day (whichever is lower) (based on general medical knowledge)
- Minimum age: Generally not recommended for infants <6 months without physician guidance (based on general medical knowledge)
Adult Dosing Guidelines
- Single dose: 200–400 mg every 4–6 hours (based on general medical knowledge)
- Maximum single dose: 800 mg (based on general medical knowledge)
- Maximum daily dose: 2400 mg/day for over-the-counter use; up to 3200 mg/day under physician supervision (based on general medical knowledge)
Dosing Accuracy Comparison
- Ibuprofen dosing errors: Only 26% of parents give inaccurate ibuprofen doses, compared to 62% for acetaminophen, suggesting ibuprofen dosing instructions may be clearer or simpler to follow 5
Key Safety Considerations
- Weight-based dosing superiority: Caregivers who base antipyretic dosage on weight rather than age are significantly less likely to give inaccurate doses (RR 0.71, P<0.03) 5
- High-risk population: Infants <1 year are 1.40 times more likely to receive inaccurate doses; extra vigilance is required in this age group 5
Practical Dosing Algorithm
Step 1: Obtain Accurate Weight
- Use actual body weight in kilograms for all calculations 1
- For obese patients, consider ideal body weight for acetaminophen dosing (based on general medical knowledge)
Step 2: Calculate Single Dose
- Acetaminophen: Multiply weight (kg) × 10–15 mg/kg 1
- Ibuprofen: Multiply weight (kg) × 5–10 mg/kg (based on general medical knowledge)
Step 3: Verify Maximum Limits
- Acetaminophen: Single dose ≤1000 mg; daily total ≤4000 mg (or 3000 mg for chronic use) 2, 3
- Ibuprofen: Single dose ≤800 mg; daily total ≤2400 mg (based on general medical knowledge)
Step 4: Account for All Sources
- Review ALL medications for hidden acetaminophen (combination cold/flu products, prescription opioid combinations) 2
- Educate caregivers that acetaminophen content from all sources counts toward the daily maximum 2