Mefenamic Acid Dosage and Usage for Pain Management
For pain management, mefenamic acid should be administered at 500 mg as an initial dose followed by 250 mg every 6 hours as needed, usually not exceeding one week of use. 1
Indications and Formulations
Mefenamic acid is a non-steroidal anti-inflammatory drug (NSAID) available in capsule form (250-500 mg) with the following key characteristics:
- Time to onset: approximately 30+ minutes 2
- Maximum daily dose: 4 × 500 mg (2000 mg total) 2
- Primary cautions: Gastrointestinal and renal toxicity 2
Specific Dosing Recommendations by Condition
Acute Pain
- Initial dose: 500 mg
- Maintenance dose: 250 mg every 6 hours as needed
- Maximum duration: Usually not to exceed one week 1
Primary Dysmenorrhea
- Initial dose: 500 mg
- Maintenance dose: 250 mg every 6 hours
- Timing: Start with onset of menstrual bleeding and associated symptoms
- Duration: Typically not necessary for more than 2-3 days 1
Efficacy Evidence
Mefenamic acid has demonstrated effectiveness in:
Acute postoperative pain: The Number Needed to Treat (NNT) for at least 50% pain relief over 6 hours with a single dose of mefenamic acid 500 mg compared to placebo was 4.0 3
Primary dysmenorrhea: Studies show complete relief of all symptoms in 88.6% of patients when administered at 500 mg every 8 hours for up to 3 days during menstruation 4
Safety Considerations
- Use the lowest effective dose for the shortest duration consistent with individual treatment goals 1
- Monitor for gastrointestinal bleeding, ulceration, and perforation 1
- Exercise caution in patients with:
- History of gastrointestinal disorders
- Renal impairment
- Cardiovascular disease
Comparison with Other Analgesics
Mefenamic acid is classified as a WHO Step I analgesic (for mild pain) 2. In the WHO pain ladder approach:
- For mild pain (NRS: 1-4): Non-opioid analgesics like mefenamic acid are recommended
- For moderate pain (NRS: 5-7): Consider combining with weak opioids
- For severe pain: Strong opioids are typically required
Important Caveats
- Mefenamic acid should not be used for longer than one week for acute pain management due to increased risk of adverse effects 1
- For primary dysmenorrhea, limiting use to 2-3 days per menstrual cycle is recommended 1
- Some studies suggest that other NSAIDs may have better efficacy profiles for certain conditions 5, 6
- Always consider gastroprotection when NSAIDs are used over a prolonged period 2
Monitoring
- Monitor for signs of gastrointestinal bleeding or ulceration
- Assess renal function periodically during extended use
- Evaluate pain control and adjust dosing as needed within the recommended parameters
When prescribing mefenamic acid, carefully weigh the potential benefits against risks, particularly in patients with pre-existing gastrointestinal or renal conditions.