A child weighing [weight] kg requires Tylinol (160 mg/5 mL) at 15 mg/kg per dose; what volume in milliliters should be administered?

Acetaminophen (Tylenol) Dosing Calculation

For a child requiring acetaminophen at 15 mg/kg/dose with a concentration of 160 mg/5 mL, multiply the child's weight in kilograms by 0.47 to determine the volume in milliliters.

Dosing Formula and Calculation

• The recommended dose is 15 mg/kg/dose, which represents the upper end of the standard 10-15 mg/kg dosing range for acetaminophen in children 1
• With a concentration of 160 mg/5 mL, this equals 32 mg/mL
• Calculation steps:
  1. Calculate total mg needed: Weight (kg) × 15 mg/kg = Total mg
  2. Convert to mL: Total mg ÷ 32 mg/mL = Volume in mL
  3. Simplified formula: Weight (kg) × 0.46875 ≈ 0.47 mL/kg

Practical Dosing Examples by Weight

• 10 kg child: 10 × 15 = 150 mg ÷ 32 = 4.7 mL
• 15 kg child: 15 × 15 = 225 mg ÷ 32 = 7.0 mL
• 20 kg child: 20 × 15 = 300 mg ÷ 32 = 9.4 mL
• 25 kg child: 25 × 15 = 375 mg ÷ 32 = 11.7 mL

These calculations maintain dosing within the established 10-15 mg/kg range 1

Rounding Considerations for Home Administration

• Acetaminophen allows up to 5% rounding for ease of home measurement, based on expert consensus 2
• For the examples above, acceptable rounded doses would be:
  • 4.7 mL can round to 4.5-5.0 mL (5% range: 4.5-4.9 mL)
  • 7.0 mL remains 7.0 mL (already a convenient measurement)
  • 9.4 mL can round to 9.5 mL (5% range: 8.9-9.9 mL)
  • 11.7 mL can round to 12.0 mL (5% range: 11.1-12.3 mL)

Critical Dosing Principles

• Weight-based dosing is superior to age-based dosing for accuracy, particularly in infants under 1 year who have the highest risk of misdosing 3
• Caregivers who base dosing on weight rather than age are significantly less likely to give inaccurate doses (RR 0.71, P < 0.03) 3
• The 15 mg/kg dose should be administered every 4-6 hours as needed, not to exceed 5 doses in 24 hours 1

Common Pitfalls to Avoid

• Do not use age-based dosing charts when weight is available, as 62% of acetaminophen doses given by parents using non-weight-based methods are inaccurate 3
• Infants under 1 year are at highest risk for dosing errors (RR 1.40 for inaccurate dosing) 3
• Ensure caregivers understand that dosing is based on current weight, not historical weight or estimated weight 3
• Use measuring devices marked in milliliters rather than household teaspoons, which vary significantly in volume 3