What is the appropriate ibuprofen (Motrin) dose for a 6‑month‑old infant weighing at least 5 kg with no contraindicating conditions?

Ibuprofen (Motrin) Dosing for a 6-Month-Old Infant

For a 6-month-old infant weighing at least 5 kg, administer ibuprofen 10 mg/kg per dose orally every 6-8 hours as needed for fever or pain, with a maximum of 3-4 doses per day (total daily dose not exceeding 30-40 mg/kg). 1, 2

Weight-Based Dosing

• The standard dose is 10 mg/kg per dose, which can be given every 6-8 hours 1
• For infants weighing 5-7 kg (approximately 6 months old), this translates to 50-70 mg per dose 2
• The maximum daily dose should not exceed 30-40 mg/kg per day, which means no more than 3-4 doses in 24 hours 2, 3

Age and Safety Considerations

• Ibuprofen is generally not recommended for infants under 6 months of age according to American Academy of Pediatrics guidelines 1
• However, recent evidence demonstrates that short-term use is considered safe in infants older than 3 months who weigh above 5-6 kg when special attention is given to hydration 2
• The FDA has approved intravenous ibuprofen for children older than 6 months, and pharmacokinetic studies show comparable safety profiles in infants 1-6 months of age 4

Critical Safety Precautions

Hydration status is paramount - ibuprofen should never be given to infants with:

• Diarrhea and vomiting (with or without fever) 3
• Signs of dehydration, as this significantly increases the risk of renal damage 3

Absolute contraindications include:

• Neonates (under 1 month) 3
• Known sensitivity to ibuprofen or other NSAIDs 3
• Active varicella infection 3
• Wheezing or persistent asthma 3

Route of Administration

• Oral administration is strongly preferred over rectal suppositories 2
• The rectal route has been shown to have erratic absorption, especially in young infants, making it less reliable for consistent dosing 2

Dosing Interval and Duration

• The dosing interval is every 6-8 hours, which is longer than acetaminophen's 4-6 hour interval 1
• Maximum reduction in temperature occurs 3-4 hours after administration 5
• Ibuprofen has a longer duration of action compared to acetaminophen 5

Clinical Efficacy

• Ibuprofen at 7.5-10 mg/kg has been shown to be equally or more effective than acetaminophen as an antipyretic and analgesic 5
• The relationship between dose and response is linear over the 5-10 mg/kg range 5
• In comparative trials, ibuprofen provided additional time without fever compared to acetaminophen alone 6

Common Pitfalls to Avoid

1. Do not extrapolate dosing to premature infants - they have immature renal function and risk drug accumulation 1
2. Carefully record all dose times to avoid accidentally exceeding the maximum recommended daily dose 6
3. Do not use ibuprofen primarily as an antipyretic - it should be reserved for inflammatory pain or when acetaminophen is insufficient 3
4. Ensure adequate hydration before and during treatment, as dehydration is the primary risk factor for renal complications 3

Practical Example

For a typical 6-month-old weighing 7 kg:

• Single dose: 70 mg (10 mg/kg × 7 kg)
• Maximum daily dose: 280 mg (40 mg/kg × 7 kg)
• Dosing schedule: 70 mg every 6-8 hours, not exceeding 4 doses in 24 hours 2