Ibuprofen (Children's Motrin) Dosing for a 40-Pound Child
A 40-pound (18.2 kg) child should receive 7.5 mL of children's Motrin (ibuprofen oral suspension 100 mg/5 mL) per dose, which can be given every 6-8 hours as needed, not to exceed 4 doses in 24 hours. 1
Dosing Calculation
- Standard pediatric ibuprofen dosing is 10 mg/kg per dose for fever and pain management 1
- For a 40-pound child (18.2 kg): 18.2 kg × 10 mg/kg = 182 mg per dose
- Children's Motrin oral suspension contains 100 mg per 5 mL
- Therefore: (182 mg ÷ 100 mg) × 5 mL = approximately 9 mL per dose
- However, practical dosing rounds to 7.5-10 mL (150-200 mg) per dose based on standard weight-based dosing schedules 1
Practical Dosing Guidelines
- Children weighing 36-47 pounds typically receive 7.5 mL (150 mg) per dose using standard over-the-counter dosing charts 1
- This dose can be administered every 6-8 hours as needed
- Maximum of 4 doses in 24 hours (do not exceed 40 mg/kg/day) 1
- The medication works best when given with food to minimize gastrointestinal side effects 1
Important Safety Considerations
- Always use the measuring device that comes with the medication to ensure accurate dosing—household spoons are not accurate 1
- Do not exceed the maximum daily dose of 40 mg/kg or 4 doses in 24 hours, whichever is less 1
- For children ages 4-6 years (typical age range for 40-pound children), this dosing is appropriate and well-established 1
- Onset of fever reduction occurs within 1-2 hours, with maximum effect at approximately 3 hours 1