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# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID). It possesses analgesic, anti-inflammatory, and antipyretic properties, primarily by inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Acute pain (short-term use, typically ≤7 days).
* Primary dysmenorrhea.
## Adult Dosing
* **Initial Dose:** 500 mg orally once.
* **Maintenance Dose:** 250 mg orally every 6 hours as needed.
* **Maximum Duration:** Should not exceed 1 week of therapy.
## Pediatric Dosing
* **Adolescents (≥14 years):** Same as adult dosing.
* **Children <14 years:** Safety and efficacy have not been established. Use is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Avoid use in patients with severe renal impairment (CrCl <30 mL/min). Use with caution in mild-to-moderate impairment; monitor closely.
* **Hepatic Impairment:** Use with caution; monitor for signs of liver dysfunction.
## Contraindications
* Known hypersensitivity (including aspirin-induced asthma or urticaria).
* History of GI bleeding or perforation related to previous NSAID therapy.
* Active peptic ulcer disease 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 the ductus arteriosus).
## Adverse Effects
* **Common:** Abdominal pain, nausea, vomiting, diarrhea (may be severe), dyspepsia, dizziness, and headache.
* **Serious:** GI ulceration/perforation, myocardial infarction, stroke, fluid retention/edema, hypertension, acute renal failure, and hepatotoxicity.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding due to antiplatelet effects and gastric mucosal injury.
* **Other NSAIDs/Aspirin:** Increased risk of GI toxicity and additive side effects.
* **Antihypertensives (ACE inhibitors, ARBs, Beta-blockers, Diuretics):** Reduced efficacy of antihypertensive therapy; increased risk of renal impairment.
* **Lithium/Methotrexate:** May increase serum concentrations and the risk of toxicity due to decreased renal clearance.
## Monitoring
* Baseline and periodic CBC if used beyond 7 days (to monitor for anemia/blood dyscrasias).
* Renal function (Creatinine, BUN) and electrolytes in patients with risk factors.
* Blood pressure monitoring.
* Observe for signs/symptoms of GI bleeding (melena, hematemesis).
## Clinical Pearls
* **GI Sensitivity:** Mefenamic acid is known for a higher incidence of diarrhea compared to other NSAIDs; discontinue if diarrhea occurs.
* **Short-term Focus:** Due to its unfavorable side effect profile with chronic use, it is strictly intended for short-term symptomatic relief.
* **Administration:** Administer with food or milk to minimize GI irritation.
* **Cardiovascular Risk:** Like all non-aspirin NSAIDs, it carries a boxed warning regarding an increased risk of serious cardiovascular thrombotic events.
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*Disclaimer: This information is for educational purposes only. Always verify drug dosages, contraindications, and interaction data against the most current institutional guidelines or official prescribing information (e.g., FDA/EMA labels) before administration.*
