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# Meftal (Mefenamic Acid)
## Overview
Mefenamic acid is an anthranilic acid derivative, non-steroidal anti-inflammatory drug (NSAID) that inhibits prostaglandin synthesis via COX-1 and COX-2 inhibition. It also possesses some peripheral and central analgesic activity.
## Primary Indications
* Primary dysmenorrhea (common clinical use).
* Short-term management of mild to moderate acute pain (typically ≤ 7 days).
* Treatment of menorrhagia (off-label/varies by region).
## Adult Dosing
* **Acute Pain/Dysmenorrhea:** 500 mg orally initially, followed by 250 mg every 6 hours as needed.
* **Maximum Duration:** Should not exceed 7 days.
* **Maximum Dosage:** 1,500 mg per 24 hours.
## Pediatric Dosing
* **Children ≥ 14 years:** Use adult dosing guidelines if clinically indicated.
* **Children < 14 years:** Safety and efficacy have not been established. Use is generally avoided in pediatric populations unless under specialist supervision.
## Dose Adjustments
* **Renal Impairment:** Contraindicated in patients with severe renal impairment (CrCl < 30 mL/min). Use with extreme caution and monitor closely in mild to moderate impairment.
* **Hepatic Impairment:** Avoid in patients with severe hepatic impairment; monitor closely for transaminase elevations.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs (risk of cross-reactivity).
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Active peptic ulceration or inflammatory bowel disease.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Severe renal or hepatic failure.
* Third trimester of pregnancy (risk of premature closure of ductus arteriosus).
## Adverse Effects
* **Gastrointestinal (Most common):** Nausea, abdominal pain, diarrhea (can be dose-limiting), and ulceration/GI bleeding.
* **Renal:** Fluid retention, edema, risk of acute kidney injury.
* **Cardiovascular:** Increased risk of thrombotic events (myocardial infarction or stroke) with long-term use.
* **CNS:** Dizziness, headache, drowsiness.
## Key Drug Interactions
* **Anticoagulants (Warfarin):** Increased risk of bleeding; monitor INR frequently.
* **Other NSAIDs/Aspirin:** Additive GI toxicity; increases bleeding risk.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive efficacy and increased risk of renal impairment.
* **Lithium:** May increase serum lithium concentrations to toxic levels.
* **Methotrexate:** Potential for increased methotrexate toxicity due to decreased renal clearance.
## Monitoring
* **Renal Function:** Serum creatinine and electrolytes periodically during chronic use.
* **GI:** Signs/symptoms of occult blood loss or dyspepsia.
* **Blood Pressure:** Monitor for exacerbations of hypertension.
* **Hepatic:** Liver function tests if symptoms of hepatotoxicity occur.
## Clinical Pearls
* **GI Sensitivity:** Mefenamic acid is historically associated with higher rates of diarrhea compared to other NSAIDs. Administering with food may reduce GI irritation but generally does not mitigate the risk of diarrhea.
* **Short-term only:** It is strictly intended for short-term use. Chronic use significantly elevates the risk of severe GI, renal, and cardiovascular events.
* **Ductus Arteriosus:** Like other NSAIDs, it crosses the placenta; avoid in the third trimester.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice protocols and prescribing information can vary by region and individual patient factors. Always verify specific dosing, safety warnings, and contraindications via official local prescribing inserts or institutional guidelines before administration.
