For a 9.5 kg infant, what is the appropriate acetaminophen (Tylenol) dose in milligrams per administration?

Acetaminophen Dosing for a 9.5 kg Infant

For a 9.5 kg infant, administer 95–142.5 mg of acetaminophen per dose, which translates to approximately 4–6 mL of standard 120 mg/5 mL suspension, given every 4–6 hours as needed (maximum 5 doses per 24 hours). 1

Weight-Based Calculation

• The American Academy of Pediatrics recommends 10–15 mg/kg per dose for infants, administered every 4–6 hours. 1
• For a 9.5 kg infant: 9.5 kg × 10 mg/kg = 95 mg (lower end) and 9.5 kg × 15 mg/kg = 142.5 mg (upper end) per dose. 1
• The practical dose is 95–140 mg per administration for ease of measurement with standard formulations. 1

Formulation-Specific Dosing

Using 120 mg/5 mL Suspension (24 mg/mL)

• Administer 4–6 mL per dose (96–144 mg), which aligns with the weight-based calculation. 1
• This is the most commonly available infant acetaminophen concentration. 1

Using 160 mg/5 mL Suspension (32 mg/mL)

• Administer 3–4.5 mL per dose (96–144 mg) if this formulation is available. 1

Critical Safety Parameters

• Maximum single dose: 15 mg/kg (142.5 mg for this infant). 1
• Minimum dosing interval: 4 hours between doses—never administer more frequently. 1
• Maximum frequency: 4–5 doses per 24 hours. 1
• Maximum daily dose: 75 mg/kg/day, which equals approximately 712.5 mg/day for a 9.5 kg infant. 1

Practical Prescribing Example

• Prescription: Acetaminophen oral suspension 120 mg/5 mL, give 5 mL (120 mg) every 4–6 hours as needed for fever or pain. 1
• Instructions to caregivers: Use the provided oral syringe to measure exactly 5 mL; do not exceed 5 doses in 24 hours; maintain at least 4 hours between doses. 1
• Maximum doses per day: 5 doses (total 600 mg/day), which remains well below the 712.5 mg/day maximum for this weight. 1

Common Pitfalls to Avoid

• Do not use adult formulations in infants, as dosing errors are common when caregivers attempt to calculate fractional doses from 325 mg or 500 mg tablets. 2
• Never exceed 75 mg/kg/day total daily dose, as repeated supratherapeutic dosing (even when individual doses appear "safe") has caused fatal hepatotoxicity in children. 2
• Avoid dosing more frequently than every 4 hours, even if fever persists, as this rapidly approaches toxic cumulative exposure. 1, 2
• Ensure accurate measurement devices are provided—household spoons are unreliable and lead to dosing errors. 1

When to Reassess

• If fever or pain persists despite appropriate acetaminophen dosing at maximum frequency for 24–48 hours, the child requires medical reevaluation rather than dose escalation. 1
• Hepatotoxicity from therapeutic misadventure typically presents 1–3 days after repeated excessive dosing, so caregivers must be counseled on strict adherence to dosing limits. 2, 3