Pediatric Dose of Mefenamic Acid for Fever
The recommended dose of mefenamic acid for fever in children is 6-6.5 mg/kg per dose, administered orally every 6-8 hours, not to exceed 25 mg/kg/day or 500 mg per dose. 1, 2
Weight-Based Dosing Algorithm
For a child with fever, calculate the dose as follows:
- Single dose: 6 mg/kg (this is the most commonly studied and effective antipyretic dose) 1, 2
- Maximum single dose: 500 mg 2
- Dosing interval: Every 6-8 hours as needed 2
- Maximum daily dose: 25 mg/kg/day 2
Practical Examples:
- 10 kg child: 60 mg per dose (6 mg/kg × 10 kg)
- 15 kg child: 90 mg per dose (6 mg/kg × 15 kg)
- 20 kg child: 120 mg per dose (6 mg/kg × 20 kg)
- 30 kg child: 180 mg per dose (6 mg/kg × 30 kg)
- 50 kg child: 300 mg per dose (6 mg/kg × 50 kg)
Evidence Supporting This Dosing
The 6 mg/kg dose demonstrates superior antipyretic efficacy compared to standard-dose paracetamol (15 mg/kg), with faster temperature reduction and longer duration of action. 1 In a randomized controlled trial, mefenamic acid 6 mg/kg achieved temperature normalization in 84.90±30.42 minutes, significantly faster than standard-dose paracetamol at 97.50±26.60 minutes. 1
Historical studies identified 4 mg/kg as the optimal antipyretic dose, showing 2.5 times the efficacy of acetylsalicylic acid or paracetamol. 3 However, more recent evidence supports 6-6.5 mg/kg as the preferred dose, demonstrating a temperature drop of 3.5°F over 4 hours compared to 2.44°F with paracetamol. 2
Critical Clinical Considerations
When to use mefenamic acid:
- Reserve for pain or inflammatory conditions rather than simple fever, as NSAIDs carry greater safety concerns than paracetamol 1, 4
- Consider when paracetamol or ibuprofen have been ineffective 2
- Appropriate for fever associated with dysmenorrhea, dental pain, or musculoskeletal pain in older children 2
When to avoid mefenamic acid:
- Dehydration: NSAIDs including mefenamic acid should not be used in dehydrated children due to renal toxicity risk 4
- Severe hepatic or renal failure: Use is contraindicated 4
- Severe malnutrition: Caution advised 4
- Age <6 months: Insufficient safety data in this age group 2
- Active gastrointestinal disease: NSAIDs increase risk of GI bleeding 4
Common Pitfalls to Avoid
- Do not use mefenamic acid as first-line antipyretic: Paracetamol (15-20 mg/kg) or ibuprofen (10 mg/kg) should be first-line agents for simple fever 1, 4
- Do not combine or alternate with other NSAIDs: This increases toxicity risk without improving efficacy 4
- Do not dose by age alone: Always calculate based on actual weight 4
- Do not exceed maximum daily dose: Risk of toxicity increases significantly above 25 mg/kg/day 2
- Do not use physical cooling methods concurrently: These are discouraged except in hyperthermia 4
Duration of Action
Mefenamic acid demonstrates continued antipyretic activity beyond 4 hours, with time to next fever spike of 8.82±3.83 hours compared to 5.07±2.66 hours for standard-dose paracetamol. 1 This longer duration may reduce dosing frequency, though the precise duration of extended efficacy requires further quantification. 2