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# Meftal (Mefenamic Acid)
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID). It exerts analgesic, anti-inflammatory, and antipyretic effects primarily through non-selective inhibition of cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Acute pain relief (short-term use).
* Primary dysmenorrhea.
* *Off-label:* Management of heavy menstrual bleeding.
## Adult Dosing
* **Standard dose:** 500 mg orally initially, followed by 250 mg every 6 hours as needed.
* **Maximum duration:** Strictly limited to 7 days of treatment due to toxicity risks.
## Pediatric Dosing
* **Children > 14 years:** Follow adult dosing.
* **Children < 14 years:** Safety and efficacy are not established. Use is generally not recommended in clinical guidelines.
## Dose Adjustments
* **Renal Impairment:** Contraindicated in severe renal impairment (CrCl < 30 mL/min). Use with extreme caution in mild-to-moderate impairment.
* **Hepatic Impairment:** Use with caution; monitor for hepatotoxicity. Dose reduction may be required.
## Contraindications
* History of hypersensitivity (including aspirin or other NSAIDs).
* Active peptic ulceration or inflammatory bowel disease (IBD).
* Severe renal, hepatic, or cardiac failure.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* History of GI bleeding or perforation.
## Adverse Effects
* **Gastrointestinal:** Nausea, diarrhea (often dose-limiting), abdominal pain, GI ulceration/perforation.
* **Renal:** Fluid retention, edema, acute renal failure, interstitial nephritis.
* **Cardiovascular:** Hypertension, potential increased risk of thrombotic events (like other NSAIDs).
* **Central Nervous System:** Dizziness, headache, drowsiness.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding due to anti-platelet effects and gastric mucosal injury.
* **Antihypertensives (ACE inhibitors, Diuretics):** Reduced efficacy; risk of acute renal failure.
* **Other NSAIDs/Corticosteroids:** Increased risk of GI toxicity.
* **Lithium/Methotrexate:** NSAIDs may decrease clearance, increasing serum concentrations and toxicity.
## Monitoring
* **Renal function:** Serum creatinine, BUN, and urine output.
* **GI:** Monitor for signs of occult blood loss or dyspepsia.
* **Blood Pressure:** Regular monitoring, especially in hypertensive patients.
* **Complete Blood Count (CBC):** Periodic monitoring if used for chronic (though non-recommended) durations to monitor for anemia.
## Clinical Pearls
* **Duration Limit:** Mefenamic acid carries a higher risk of severe GI adverse effects (specifically diarrhea and mucosal injury) compared to other NSAIDs; it is strictly intended for short-term use (≤ 7 days).
* **Food Intake:** Take with food or milk to reduce gastrointestinal irritation.
* **Water/Electrolytes:** Instruct patients to maintain adequate hydration to protect renal function.
* **Self-Limitation:** If symptoms persist beyond the 7-day window, the patient must be re-evaluated; do not extend therapy.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice protocols vary by region and institution. Always verify dosages, contraindications, and drug interactions using current, peer-reviewed resources such as the manufacturer’s product insert, BNF, or Lexicomp before prescribing or administering medication.
