Diclofenac Dosing in Children
Route-Specific Dosing Recommendations
For children aged 1-12 years, the recommended single dose of diclofenac is 0.3 mg/kg for intravenous administration, 0.5 mg/kg for rectal suppositories, and 1 mg/kg for oral formulations, based on pharmacokinetic modeling that yields equivalent drug exposure to adult dosing. 1
Intravenous Route
- Dose: 0.3 mg/kg per dose 1
- Dosing interval: Every 8 hours 2
- Maximum daily dose: Not to exceed 75 mg/day (extrapolated from adult OTC maximum) 3
Rectal Route
- Dose: 0.5 mg/kg per dose 1
- Dosing interval: Every 8 hours 2
- Rectal administration is commonly used (80% of pediatric anesthetists) but has lower bioavailability (35%) compared to oral suspension 2, 1
Oral Route
- Dose: 1 mg/kg per dose 2, 1
- Dosing interval: Every 6-8 hours 3
- Maximum daily dose: 75 mg/day for children 3
- Oral suspension has higher bioavailability (36%) than suppositories and is the preferred oral formulation 1
Age Restrictions and Licensing
- Minimum age: Diclofenac is licensed for children over 1 year of age 2
- Despite licensing restrictions, 86% of pediatric anesthetists report using NSAIDs (including diclofenac) in infants under 1 year, though this represents off-label use 2
- For children weighing >30 kg, dosing may transition toward adult regimens using the formula: (weight + 30)% of adult dose 4
Clinical Context and Practical Considerations
Common Clinical Uses
- Diclofenac is most commonly used intraoperatively (78% of pediatric anesthetists), while ibuprofen is preferred postoperatively (73%) 2
- For adenotonsillectomy, 57% of pediatric anesthetists include NSAIDs in their analgesic regimen 2
- Only 21% use NSAIDs in intensive care settings 2
Pharmacokinetic Rationale
- The recommended doses are derived from population pharmacokinetic modeling in 111 children aged 1-14 years, designed to achieve area-under-the-curve equivalence to a 50 mg adult dose 1
- Diclofenac has a short plasma half-life (1-2 hours) but persists longer in synovial fluid, supporting 6-8 hour dosing intervals 5, 3
- Peak plasma concentrations occur 30 minutes after oral administration, providing rapid onset of analgesia 3
Important Caveats
- Avoid extrapolating adult mg/kg dosing directly to children—pediatric doses differ significantly due to altered pharmacokinetics 1
- The most common adverse effects are gastrointestinal, though these occur less frequently than with aspirin or indomethacin 5
- Maximum treatment duration for OTC use should not exceed 5 days for pain or 3 days for fever 3
- There is a significant knowledge gap regarding pharmacokinetic and pharmacodynamic data in infants, making dosing in this age group largely empirical 2