What is the recommended dosage of Mefenamic acid (Nonsteroidal Anti-Inflammatory Drug - NSAID) for pain management?

Mefenamic Acid Dosing for Pain Management

For acute pain in adults and adolescents ≥14 years, give 500 mg as an initial dose followed by 250 mg every 6 hours as needed, with a maximum daily dose of 2000 mg (4 × 500 mg), and treatment should not exceed one week. 1

Standard Dosing Regimens

Acute Pain Management

• Initial dose: 500 mg orally 1
• Maintenance dose: 250 mg every 6 hours as needed 1
• Maximum daily dose: 2000 mg (4 × 500 mg) 2
• Duration: Treatment should not exceed one week 1

Primary Dysmenorrhea

• Initial dose: 500 mg at onset of bleeding and symptoms 1
• Maintenance dose: 250 mg every 6 hours 1
• Duration: Typically 2-3 days per menstrual cycle 1
• Alternative regimen: 500 mg every 8 hours for maximum 3 days during menstruation has shown 88.6% complete symptom relief 3

Postoperative Pain

• Single dose: 500 mg provides effective analgesia with NNT of 4.0 for at least 50% pain relief over 6 hours 4
• Follow standard acute pain dosing thereafter (250 mg every 6 hours) 1

Clinical Context and WHO Pain Ladder

Mefenamic acid is classified as a WHO Step I analgesic for mild pain (NRS 1-4), with onset of action within 30 minutes 2. It can be used alone or combined with opioids for moderate to severe pain 2.

Critical Safety Considerations

Gastrointestinal Protection

• Gastric protection is mandatory when NSAIDs are used over prolonged periods 2
• Avoid in patients with active peptic ulcer disease 2
• Use extreme caution in patients with history of peptic ulcer disease or significant alcohol use 2

Renal Toxicity

• Exercise heightened vigilance when using mefenamic acid in patients at risk of nephrotoxicity 2
• Higher doses carry increased risk of renal adverse effects 2

Bleeding Risk

• Use caution in patients at risk of bleeding 2
• Concurrent use with anticoagulants significantly increases bleeding risk 2

Administration Guidelines

• Always administer with food to minimize gastrointestinal side effects 1
• Use the lowest effective dose for the shortest duration consistent with treatment goals 1
• After observing initial response, adjust dose and frequency to individual patient needs 1

When to Stop or Switch Therapy

• If two NSAIDs (including mefenamic acid) are tried successively without efficacy, switch to an alternative analgesic approach such as opioids or non-pharmacologic interventions rather than trialing additional NSAIDs 2
• Discontinue if gastrointestinal or renal toxicity develops 2

Comparative Efficacy

Mefenamic acid 500 mg every 8 hours demonstrated similar efficacy to 250 mg every 6 hours for dysmenorrhea, with both regimens providing substantial pain relief 3, 5. The every-6-hour dosing (250 mg) may offer more consistent analgesia for acute pain conditions 1.