What is the recommended dosing of mefenamic acid for children aged six months or older, including weight‑based dose, maximum daily dose, single‑dose limit, and contraindications?

Mefenamic Acid Dosing in Children

Primary Recommendation

Mefenamic acid should be dosed at 6 mg/kg per dose in children aged 6 months and older, with a maximum single dose not exceeding 500 mg and a maximum daily dose of 1500 mg (divided into 3 doses every 8 hours). 1

Weight-Based Dosing Algorithm

• Standard dose: 6 mg/kg per dose, administered every 8 hours 1
• Maximum single dose: 500 mg (regardless of weight) 1
• Maximum daily dose: 1500 mg per day (three 500 mg doses) 1
• Minimum age: 6 months old 1

Practical Calculation Example

• For a 20 kg child: 20 kg × 6 mg/kg = 120 mg per dose, given every 8 hours 1
• For a 40 kg child: 40 kg × 6 mg/kg = 240 mg per dose, given every 8 hours 1
• For children ≥83 kg: Maximum 500 mg per dose (do not exceed based on weight calculation) 1

Clinical Efficacy and Comparative Data

• Mefenamic acid (6 mg/kg) demonstrates equivalent antipyretic efficacy to high-dose paracetamol (20 mg/kg) and superior efficacy compared to standard-dose paracetamol (15 mg/kg) 1
• The mean time to reach normal temperature with mefenamic acid is approximately 85 minutes, compared to 97.5 minutes with standard-dose paracetamol 1
• Temperature reduction at 60 minutes averages 0.45°C with mefenamic acid versus 0.33°C with standard-dose paracetamol 1
• Duration of antipyretic effect is longer with mefenamic acid (8.82 hours) compared to standard-dose paracetamol (5.07 hours), though this difference did not reach statistical significance 1

Important Clinical Caveats

Mefenamic acid should be reserved for pain management or inflammatory conditions rather than routine fever control. 1 The 2022 randomized controlled trial demonstrated that high-dose paracetamol (20 mg/kg) achieves similar antipyretic effects with a better safety profile, suggesting NSAIDs like mefenamic acid should be avoided for simple fever management. 1

Safety Considerations and Contraindications

• Gastrointestinal toxicity: Mefenamic acid causes more upper gastrointestinal tract lesions than other NSAIDs with prolonged use 2
• Renal insufficiency: Occasional renal impairment has been reported, particularly with extended therapy 2
• Systemic toxicity: Begins at relatively low doses above the maximum daily dose compared to other NSAIDs 2
• Hydration status: Ensure adequate hydration before administration, as NSAIDs can affect renal function 1
• Duration limit: Should not be used for prolonged periods due to increased adverse effect profile 2

Monitoring Requirements

• Monitor for gastrointestinal symptoms (nausea, vomiting, abdominal pain) during therapy 1, 2
• If fever persists beyond 48-72 hours despite treatment, medical reevaluation is necessary 1
• Watch for signs of dehydration or decreased oral intake, which warrant immediate medical assessment 1

Alternative Recommendations

First-line antipyretic therapy should be paracetamol at 15-20 mg/kg per dose every 6-8 hours (maximum 4 doses per 24 hours), reserving mefenamic acid for pain or inflammatory conditions where its anti-inflammatory properties are specifically needed. 1 Ibuprofen at 10 mg/kg per dose every 6-8 hours is another acceptable alternative with a more favorable safety profile than mefenamic acid. 3