What is Ponstan (Mefenamic Acid)?
Ponstan is the brand name for mefenamic acid, a nonsteroidal anti-inflammatory drug (NSAID) used primarily for treating mild to moderate pain, particularly dysmenorrhea (menstrual pain), and other acute pain conditions. 1, 2, 3, 4, 5
Drug Classification and Mechanism
Mefenamic acid belongs to the fenamate class of NSAIDs and works through:
- COX-1 inhibition (highly selective COX-1 inhibitor) 6
- Blocking prostaglandin synthesis to reduce pain and inflammation
- Additional unique mechanisms including E-type prostanoid (EP) receptor blockade 7
Clinical Uses
Mefenamic acid is indicated for:
Primary indications:
- Mild pain (WHO Step I analgesic ladder) 1, 2, 3, 4, 5
- Dysmenorrhea (menstrual pain) 8, 9
- Menorrhagia (heavy menstrual bleeding) 10
- Acute postoperative pain 9
- Dental pain and headache 9
Specific gynecological applications:
- Treatment of heavy or prolonged menstrual bleeding in copper IUD users 11
- Bleeding irregularities with contraceptive implants 11
Dosing
Standard adult dosing:
- Available as capsules: 250-500 mg 1, 2, 3, 4, 5
- Maximum daily dose: 2000 mg (4 × 500 mg) 1, 2, 3, 4, 5
- Time to onset: approximately 30 minutes 1, 2, 3, 4, 5
For menstrual bleeding with IUD use:
- Short-term treatment for 5-7 days during bleeding episodes 11
- 500 mg three times daily for 5 days has shown efficacy 11
Important Safety Considerations
Cautions (applicable to all NSAIDs including mefenamic acid):
- Gastrointestinal toxicity - risk of ulcers, bleeding, perforation 1, 2, 3, 4, 5
- Renal toxicity - use caution in patients with kidney disease 1, 2, 3, 4, 5
- Gastric protection recommended with prolonged use 1
- Increased bleeding risk - avoid in patients on anticoagulants or with bleeding disorders 1
Specific to older adults:
- Avoid in adults >75 years due to increased gastrointestinal bleeding risk 12
- Higher risk of cardiovascular events and heart failure exacerbation 12
Fixed drug eruption:
- Mefenamic acid can cause fixed drug eruptions (skin reactions that recur in the same location) 10
- Lesions typically become inflamed within hours of drug intake 10
Comparative Efficacy
Pain relief:
- NNT (number needed to treat) for 50% pain relief over 6 hours with 500 mg dose: 4.0 (meaning 1 in 4 patients will achieve significant pain relief) 9
- Effective for moderate to severe acute postoperative pain 9
Menstrual bleeding:
- Multiple studies demonstrate statistically significant reductions in menstrual blood loss 11
- More effective than placebo for heavy bleeding in IUD users 11
Clinical Context
Mefenamic acid occupies a specific niche among NSAIDs. While general NSAID use has increased, mefenamic acid use has declined 8. However, it maintains relevance for:
- Pain syndromes requiring short-term management
- Gynecological disorders, particularly menstrual-related conditions
- Situations where its unique pharmacological properties (EP receptor blockade, potential NLRP3 inflammasome inhibition) may provide advantages 7, 8
Key Prescribing Points
- Use the lowest effective dose for the shortest duration to minimize adverse effects
- Consider gastric protection (proton-pump inhibitors) for prolonged use 1
- Monitor renal function in at-risk patients
- Avoid in patients with active peptic ulcer disease or significant cardiovascular disease
- Not recommended as first-line in older adults due to safety concerns 12