Dosing for a 16.5 kg Child
For a 16.5 kg child, give ibuprofen (Motrin) 165 mg as a single dose and diphenhydramine (Benadryl) 16.5 mg as a single dose.
Ibuprofen (Motrin) Dosing
The standard pediatric dose of ibuprofen is 10 mg/kg per dose 1. For a child weighing 16.5 kg:
- Calculated dose: 10 mg/kg × 16.5 kg = 165 mg
- This can be given every 6-8 hours as needed, but you asked for the one-time dose
- Maximum single dose should not exceed 400 mg 1
- Maximum daily dose is 40 mg/kg/day (660 mg for this child) 1
Practical Administration
- Children's ibuprofen liquid is typically 100 mg/5 mL
- For 165 mg, give approximately 8.25 mL (or round to 8 mL for practical dosing, which equals 160 mg)
- Administer with food to improve gastrointestinal tolerability 2
Diphenhydramine (Benadryl) Dosing
The standard pediatric dose of diphenhydramine is 1 mg/kg per dose 1. For a child weighing 16.5 kg:
- Calculated dose: 1 mg/kg × 16.5 kg = 16.5 mg
- Can be given every 6 hours as needed
- Maximum single dose is 25-50 mg 1
Practical Administration
- Children's diphenhydramine liquid is typically 12.5 mg/5 mL
- For 16.5 mg, give approximately 6.6 mL (or round to 6.5 mL for practical dosing)
- Note: Some formulations may be different concentrations, so always verify the concentration on the bottle 2
Critical Safety Considerations
Avoid combination products that contain either medication 2. Many over-the-counter cold and allergy products contain ibuprofen or diphenhydramine, and inadvertent double-dosing is a common and dangerous error 2.
- Do not exceed maximum daily doses for either medication
- Space doses appropriately (minimum 6 hours between doses)
- Monitor for side effects: drowsiness with diphenhydramine, gastrointestinal upset with ibuprofen 1