What is the recommended diclofenac dosage for children based on age and weight, including oral and rectal routes, and what are the contraindications?

Diclofenac Dosing for Pediatric Patients

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

Route-Specific Dosing Recommendations

Oral Administration

• 1 mg/kg as a single dose (maximum 50 mg per dose) 1, 2
• This dose achieves equivalent drug exposure (AUC) in children aged 1-12 years compared to the standard 50 mg adult dose 1, 2
• Can be administered every 8 hours for ongoing pain management 3
• Bioavailability of oral suspension is approximately 36% 1

Rectal Administration

• 0.5 mg/kg as a single dose via suppository 1
• Rectal route has higher bioavailability (63%) compared to oral suspension, hence the lower mg/kg requirement 1
• Commonly used intraoperatively by 80% of pediatric anesthesiologists 3

Intravenous Administration

• 0.3 mg/kg as a single dose 1
• Rarely used (only 9% of practitioners), but provides most predictable drug levels 3

Age and Weight Considerations

• Minimum age: 1 year for all routes of administration 1, 4
• Weight range studied: 9-37 kg (approximately 1-12 years of age) 2
• Dosing is weight-based using ideal body weight, not actual weight if obese 1
• Children >12 years or >40 kg may transition to adult dosing protocols 2

Combination Therapy

When combined with acetaminophen, diclofenac 1 mg/kg plus acetaminophen 15 mg/kg achieves equivalent analgesia to acetaminophen 30 mg/kg alone. 5

• This combination allows dose reduction of both medications while maintaining efficacy 5
• Drug effects are additive, not synergistic 5
• Onset of analgesia: equilibration half-time of 0.23 hours for diclofenac vs 0.496 hours for acetaminophen 5

Dosing Interval

• Every 8 hours is the most commonly employed schedule (used by 53% of practitioners) 3
• Maximum daily dose should not exceed 3 mg/kg/day orally or 150 mg/day, whichever is lower 1, 2

Safety Profile in Children

Serious adverse reactions occur in fewer than 0.24% of children treated with diclofenac for acute pain. 4

• The types of serious adverse events mirror those seen in adults (gastrointestinal, renal, cardiovascular) 4
• No increased risk of surgical bleeding requiring intervention in perioperative settings 4
• Compared to opioids, diclofenac reduces nausea/vomiting (RR 0.6; NNT 7.7) 4
• Reduces need for rescue analgesia by 40% compared to placebo (RR 0.6; NNT 3.6) 4

Key Contraindications and Cautions

• Avoid in children <1 year of age due to lack of pharmacokinetic and safety data 1, 4
• Use caution in asthmatic children, though more safety data are needed in this population 4
• Standard NSAID contraindications apply: active GI bleeding, severe renal impairment, known hypersensitivity 4
• Not licensed for acute pain in all jurisdictions—diclofenac is approved for juvenile rheumatoid arthritis in children >1 year, but acute pain use is off-label in many regions 3

Common Prescribing Pitfalls

• Do not exceed 1 mg/kg orally based on the misconception that "more is better"—higher doses do not improve efficacy and increase toxicity risk 2
• Do not use rectal and oral doses interchangeably—rectal bioavailability is nearly double that of oral suspension, requiring dose adjustment 1
• Do not underdose the rectal route by using the same 1 mg/kg as oral; the correct rectal dose is 0.5 mg/kg 1
• Recognize that 86% of pediatric anesthesiologists use NSAIDs in infants despite limited data, highlighting widespread off-label practice 3

Clinical Context

Diclofenac is widely used for perioperative analgesia in children, particularly following tonsillectomy, dental procedures, and minor orthopedic surgery 5, 4. It provides opioid-sparing analgesia with a favorable side effect profile compared to narcotics 4. The evidence base consists primarily of perioperative studies; data for non-surgical acute pain (e.g., trauma, medical conditions) are more limited but dosing principles remain the same 1, 4.