What is the appropriate dose in milligrams of Tylenol (acetaminophen) for a child weighing 15 lb 14 oz, given a recommended dose of 15 mg/kg per dose?

Acetaminophen Dosing Calculation for 15 lb 14 oz Child

This child should receive 108 mg of acetaminophen per dose.

Weight Conversion and Calculation

• The child weighs 15 lb 14 oz, which converts to 7.2 kg (15.875 lb ÷ 2.2 lb/kg = 7.2 kg) 1
• Using the recommended dose of 15 mg/kg/dose: 7.2 kg × 15 mg/kg = 108 mg per dose 2

Critical Dosing Considerations

Always use actual measured weight, not estimated weight, when calculating pediatric medication doses. Studies demonstrate that physician weight estimates for individual children can vary dramatically—ranging from 300% overestimates to nearly 100% underestimates—making accurate prescribing impossible without actual weights 1. While doctors' estimates as a group may average correctly, the wide individual variation creates unacceptable risk for under- or overdosing 1.

Safety Parameters

• The therapeutic dose range for acetaminophen in children is typically 10-15 mg/kg per dose, given every 4-6 hours 2
• Never exceed 75 mg/kg/day or 4000 mg/day total (whichever is lower) to prevent hepatotoxicity 3, 2
• For this 7.2 kg child, the maximum daily dose would be 540 mg/day (75 mg/kg/day), allowing up to 5 doses of 108 mg if spaced appropriately 2

Common Pitfalls to Avoid

Do not use adult acetaminophen preparations for young children. In one case series of acetaminophen hepatotoxicity in children, 52% had received adult preparations, contributing to overdosing 2. Children who received 60-420 mg/kg/day for multiple days developed severe hepatotoxicity with mean peak AST levels of 10,225 IU/L, and 55% died or required liver transplantation 2.

Weight-based dosing is imperative for acetaminophen in young children because of the large variation in weight that can occur at any given age 1. Age-based dosing may lead to significant errors in this weight range 4.

Hepatotoxicity Risk

• Therapeutic doses produce plasma concentrations of 5-20 mcg/mL, well below the toxic threshold of 150 mcg/mL 3
• However, repeated supratherapeutic dosing (exceeding weight-based recommendations) in ill children has caused fatal hepatotoxicity even when individual doses seemed reasonable 2
• The toxic metabolite (NAPQI) accumulates when hepatic glutathione stores become depleted, typically only occurring with overdose, but can happen with repeated excessive dosing in vulnerable children 3, 2