Acetaminophen Dosing for a 42.91kg Child
For a child weighing 42.91kg, prescribe acetaminophen 650mg every 4-6 hours as needed, not to exceed 3000mg in 24 hours.
Weight-Based Dosing Calculation
This child falls into the adult dosing category since they weigh more than 40kg (88 lb), which is the threshold where pediatric weight-based dosing transitions to standard adult dosing 1
The standard adult dose is 650-1000mg every 4-6 hours, with a maximum daily dose of 3000-4000mg 2
I recommend starting with 650mg per dose for this child who just crossed the 40kg threshold, as this provides adequate analgesia while maintaining a safety margin 2
Maximum Daily Dose Considerations
The maximum daily dose should not exceed 3000mg (approximately 70mg/kg/day for this child), which aligns with current conservative recommendations 2
While historical FDA monograph dosing allowed up to 3900-4000mg daily, major manufacturers have voluntarily reduced maximum daily dosing to 3000-3250mg for safety 2
This conservative approach is particularly important in children who have just transitioned to adult dosing to minimize hepatotoxicity risk 3, 4
Dosing Interval
Administer every 4-6 hours as needed for pain or fever 5
Emphasize to caregivers that acetaminophen should be used at the lowest effective dose for the shortest duration necessary 6
Route of Administration
Oral administration is preferred for this weight category 5, 7
If oral route is not feasible, intravenous acetaminophen can be dosed at 15mg/kg (approximately 644mg) every 6 hours, not exceeding 60mg/kg/day (2574mg/day for this child) 5
IV formulation should be reserved for situations where enteral routes are not feasible and must be infused over 15 minutes, never as a bolus 5
Critical Safety Points
Ensure caregivers understand to account for all sources of acetaminophen, as it is commonly combined with opioids in prescription medications and found in many over-the-counter cold/flu preparations 2, 4
Acetaminophen overdose is the leading cause of acute liver injury in Western countries, making accurate dosing education essential 4
Use appropriate measuring devices (oral syringes) if liquid formulation is used, though at this weight, tablets are more practical 7