Diclofenac Dosing for a 22 kg Child
For a child weighing 22 kg, the appropriate dose of diclofenac is 22 mg (1 mg/kg) for oral administration, or 11 mg (0.5 mg/kg) for rectal administration, given every 8 hours. 1, 2
Weight-Based Dosing Algorithm
The dosing of diclofenac in children follows a straightforward weight-based calculation that varies by route of administration:
Oral Route
- Dose: 1 mg/kg every 8 hours 1
- For a 22 kg child: 22 mg per dose
- This can be administered as oral suspension or tablets
- Maximum daily dose should not exceed 3 mg/kg/day (66 mg/day for this child)
Rectal Route
- Dose: 0.5-1 mg/kg every 8 hours 1
- For a 22 kg child: 11-22 mg per dose
- The lower end (0.5 mg/kg = 11 mg) is typically used due to variable bioavailability of rectal formulations 2
Intravenous Route (if available)
- Dose: 0.3 mg/kg 2
- For a 22 kg child: 6.6 mg per dose
- This route provides more predictable pharmacokinetics but is less commonly used 2
Pharmacokinetic Rationale
The dosing recommendations are based on pharmacokinetic modeling demonstrating that these weight-based doses achieve equivalent drug exposure (AUC) to effective adult doses:
- Bioavailability varies significantly by formulation: oral suspension (36%), suppositories (63%), and dispersible tablets (35%) 2
- The higher oral dose (1 mg/kg) compensates for lower bioavailability compared to rectal administration 2
- Diclofenac reaches peak plasma concentration within 30 minutes and has a terminal half-life of 1-2 hours, supporting 8-hourly dosing 3
Clinical Context and Safety
Common pediatric uses include:
- Postoperative pain management 1, 4
- Acute musculoskeletal pain 5
- Fever reduction (though paracetamol is typically first-line) 1
Critical safety considerations:
- Diclofenac is widely used in pediatric anesthesia practice, with 78% of surveyed pediatric anesthesiologists using it intraoperatively 4
- The drug is generally well-tolerated with adverse event rates similar to ibuprofen and placebo 3
- Avoid in patients with bleeding disorders, active peptic ulcer disease, or significant renal impairment 1
- Consider combining with paracetamol for enhanced analgesia in moderate-to-severe pain 1
Practical Dosing Example for 22 kg Child
If using diclofenac 12.5 mg tablets:
- Round to nearest practical dose: Give 2 tablets (25 mg) every 8 hours orally
- This provides approximately 1.1 mg/kg, which is within the safe and effective range 1, 2
- Maximum 6 tablets (75 mg) per day
If using rectal suppositories:
- Use 12.5 mg suppository every 8 hours (0.57 mg/kg)
- This is appropriate given the higher bioavailability of rectal formulations 2
Common Pitfalls to Avoid
- Do not underdose: The 1 mg/kg oral dose is necessary due to lower bioavailability; using 0.5 mg/kg orally (appropriate for rectal) will result in inadequate analgesia 2
- Do not exceed 3 mg/kg/day total: While individual doses may be rounded up slightly for practical administration, the total daily dose should not exceed this limit 1
- Ensure adequate hydration: NSAIDs can affect renal function, particularly in dehydrated patients 1
- Consider multimodal analgesia: Combining diclofenac with paracetamol provides superior pain control compared to either agent alone 1