Acetaminophen Dosing for a 90-Pound Child
Give 410-615 mg of acetaminophen (Tylenol) every 4-6 hours, not exceeding 5 doses in 24 hours or a maximum daily dose of 2,460 mg.
Weight-Based Calculation
A 90-pound child weighs approximately 41 kg (90 lbs ÷ 2.2 = 40.9 kg).
- Standard dosing is 10-15 mg/kg per dose 1, 2, 3
- For this 41 kg child: 410 mg (10 mg/kg) to 615 mg (15 mg/kg) per dose 1
- Dosing interval: every 4-6 hours as needed 1, 2
- Maximum daily dose: 60 mg/kg per day = 2,460 mg/day 1, 3
- Never exceed 5 doses in 24 hours 1
Practical Dosing Recommendations
Since children over 40 kg can be dosed as adults, this child can receive adult formulations 4:
- 500 mg tablets: Give 1 tablet (500 mg) every 4-6 hours 4
- 325 mg tablets: Give 2 tablets (650 mg) every 4-6 hours, though this exceeds the strict 15 mg/kg maximum slightly 4
The 500 mg dose falls comfortably within the 10-15 mg/kg range and is the most practical option 1, 4.
Route of Administration
- Oral formulations (tablets, liquid suspension) are strongly preferred over rectal suppositories because they provide more rapid and consistent absorption 1, 5
- Liquid suspensions are absorbed more rapidly than suppositories and provide more consistent response 1
- Use appropriate measuring devices for liquid formulations 4
Critical Safety Points
Maximum daily limits must never be exceeded 1:
- Total daily dose must not exceed 2,460 mg (60 mg/kg) 1, 3
- Do not give more than 5 doses in 24 hours 1
- Chronic overdosing (>140 mg/kg/day for several days) carries risk of serious hepatotoxicity 3
Common Pitfall to Avoid
Parents frequently misdose acetaminophen, with studies showing 62% of caregivers give inaccurate doses 6. Weight-based dosing significantly reduces dosing errors compared to age-based or other methods 6. Always calculate the dose based on the child's actual weight in kilograms, not age alone 6.