What is the recommended dose of diclofenac (Nonsteroidal Anti-Inflammatory Drug (NSAID)) for a child?

Diclofenac Dosing in Children

For children aged 1-12 years, the recommended dose of diclofenac is 1 mg/kg orally, 0.5 mg/kg rectally, or 0.3 mg/kg intravenously as a single dose for acute pain management. 1

Route-Specific Dosing Recommendations

Oral Administration

• 1 mg/kg as a single dose is the evidence-based recommendation for children aged 1-12 years 2, 1
• This dose produces similar drug exposure (AUC) in children as a 50 mg dose in adults, which is the optimal adult dose for acute pain 2, 1
• The most commonly used dose in clinical practice is 1 mg/kg, administered every 8 hours 3
• Oral route is the most frequently used (81% of practitioners) 3

Rectal Administration

• 0.5 mg/kg as a single dose via suppository 1
• Rectal administration is commonly used (80% of practitioners) and has a bioavailability of 0.63 3, 1

Intravenous Administration

• 0.3 mg/kg as a single dose 1
• Intravenous use is less common (9% of practitioners) but provides the most predictable bioavailability 3, 1

Age and Weight Considerations

• Diclofenac is licensed for children over 1 year of age for juvenile rheumatoid arthritis 3
• Allometric size models adequately predict changes in clearance and volume of distribution with age, supporting weight-based dosing across the 1-12 year age range 2
• No dosage adjustments are required for elderly patients or children based on age alone, as no drug accumulation occurs 4

Dosing Interval

• Every 8 hours is the most commonly employed dosing schedule (53% of practitioners) 3
• The elimination half-life is approximately 1.5 hours in plasma, though the drug persists longer in synovial fluid 4, 5

Important Clinical Considerations

Bioavailability Differences

• Oral suspension has a bioavailability of 0.36, requiring higher mg/kg dosing 1
• Suppositories have a bioavailability of 0.63 1
• Dispersible tablets have a bioavailability of 0.35 1
• These differences explain why oral dosing (1 mg/kg) is higher than rectal (0.5 mg/kg) or IV (0.3 mg/kg) to achieve equivalent drug exposure 1

Common Pitfalls to Avoid

• Do not exceed 1 mg/kg for oral dosing: Higher doses are unlikely to provide additional benefit, as this dose already achieves optimal adult-equivalent exposure 2
• Avoid use in infants under 1 year: Pharmacokinetic and pharmacodynamic data are lacking in this age group, despite off-label use by some practitioners 3
• Consider renal function: While dosage adjustments may not be required for mild-moderate renal impairment, conjugate accumulation can occur in end-stage renal disease 4

Drug Interactions

• Significant interactions have been demonstrated with aspirin, lithium, digoxin, methotrexate, cyclosporin, cholestyramine, and colestipol 4
• These interactions should be considered when prescribing diclofenac in children on multiple medications 4

Administration Timing

• Diclofenac should be administered with meals to minimize gastrointestinal adverse effects 5
• Peak plasma concentrations occur 1.5-2.0 hours after oral ingestion in fasting subjects 5