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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties by non-selectively inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Treatment of mild to moderate pain.
* Treatment of primary dysmenorrhea.
## Adult Dosing
* **Acute Pain/Dysmenorrhea:** 500 mg orally initially, followed by 250 mg every 6 hours as needed.
* **Duration:** Therapy should not exceed 7 days.
## Pediatric Dosing
* **Adolescents (≥ 14 years):** Follow adult dosing (500 mg initial, then 250 mg every 6 hours).
* **Children < 14 years:** Safety and efficacy are not established; use is generally avoided.
## Dose Adjustments
* **Renal Impairment:** Avoid in patients with advanced renal disease. Use with caution in mild-to-moderate impairment; close monitoring of renal function is required.
* **Hepatic Impairment:** Use with caution; may require dose reduction or avoidance in severe hepatic dysfunction.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs (including aspirin-induced asthma/urticaria).
* History of GI bleeding or perforation related to previous NSAID therapy.
* Active peptic ulcer disease or inflammatory bowel disease.
* Treatment of perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Severe heart failure or severe renal impairment.
## Adverse Effects
* **Gastrointestinal:** Abdominal pain, diarrhea (common, can be severe), nausea, dyspepsia, peptic ulceration, GI bleeding.
* **Cardiovascular:** Edema, hypertension, increased risk of cardiovascular thrombotic events (MI, stroke).
* **Renal:** Acute kidney injury, fluid retention.
* **Hematologic:** Anemia (potential for blood loss), rare blood dyscrasias.
## Key Drug Interactions
* **Anticoagulants/Antiplatelets (e.g., Warfarin, SSRIs):** Increased risk of serious GI bleeding.
* **Diuretics, ACE inhibitors, ARBs:** Reduced antihypertensive effect; increased risk of nephrotoxicity.
* **Lithium/Methotrexate:** NSAIDs may decrease clearance, leading to potential toxicity.
* **Other NSAIDs/Corticosteroids:** Increased risk of GI toxicity and ulceration.
## Monitoring
* Baseline and periodic renal function (BUN/SCr) and liver function tests.
* Monitor for signs of GI bleeding (melena, hematemesis, unexplained anemia).
* Monitor blood pressure periodically.
* Assess for fluid retention or worsening heart failure symptoms.
## Clinical Pearls
* **Diarrhea:** Mefenamic acid is notably more likely to cause diarrhea compared to other NSAIDs; if diarrhea occurs, discontinue use immediately.
* **Short-term use:** Due to potential for serious GI and cardiovascular toxicity, it is specifically indicated for short-term use only (limit to ≤ 7 days).
* **Administration:** Take with food or milk to minimize gastrointestinal upset.
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**Educational Disclaimer:** This information is for educational purposes only. Always consult current, full prescribing information (such as the FDA/EMA label) or institutional protocols before prescribing or administering medication. Clinical judgement must be used for specific patient scenarios.
