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# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis. It possesses analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Treatment of mild to moderate pain.
* Primary dysmenorrhea.
* *Off-label:* Management of heavy menstrual bleeding (menorrhagia).
## Adult Dosing
* **Pain/Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Duration:** Therapy should not exceed 7 days.
## Pediatric Dosing
* **Children ≥ 14 years:** Same as adult dosing (500 mg initial, then 250 mg q6h for up to 7 days).
* **Children < 14 years:** Safety and efficacy have not been established. Use is generally avoided.
## Dose Adjustments
* **Renal Impairment:** Avoid in severe renal impairment (CrCl < 30 mL/min). Use with caution in mild-to-moderate impairment; monitor renal function closely.
* **Hepatic Impairment:** Use with caution; dose reduction may be required. Avoid in severe hepatic impairment.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Perioperative pain management in the context of coronary artery bypass graft (CABG) surgery.
* Active peptic ulcer disease or history of recurrent ulceration/GI bleeding.
* Severe renal or hepatic impairment.
## Adverse Effects
* **Gastrointestinal:** Nausea, vomiting, diarrhea (may be severe), abdominal pain, dyspepsia.
* **Renal/Cardiovascular:** Edema, fluid retention, hypertension, increased risk of thrombotic events (MI, stroke).
* **Hematologic:** Anemia, rare cases of leukopenia or thrombocytopenia.
* **CNS:** Dizziness, headache, nervousness.
## Key Drug Interactions
* **Anticoagulants/Antiplatelets (e.g., Warfarin, SSRIs):** Increased risk of major bleeding.
* **Other NSAIDs/Corticosteroids:** Increased risk of gastrointestinal ulceration/bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of acute kidney injury.
* **Lithium/Methotrexate:** Potential for increased serum concentrations and toxicity due to reduced renal clearance.
## Monitoring
* Baseline and periodic monitoring of Complete Blood Count (CBC).
* Renal function (BUN/SCr) and electrolytes.
* Blood pressure monitoring.
* Symptomatic assessment for gastrointestinal distress or occult bleeding.
## Clinical Pearls
* **Gastrointestinal Sensitivity:** Mefenamic acid is known to cause diarrhea more frequently than other NSAIDs; if diarrhea occurs, discontinue immediately.
* **Short Duration:** The FDA-approved labeling strictly limits therapy to 7 days due to cumulative gastrointestinal and renal toxicity risks.
* **Administration:** Take with food or milk to minimize potential gastric irritation.
* **CV Risk:** Use the lowest effective dose for the shortest duration necessary to minimize cardiovascular and gastrointestinal risks.
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**Disclaimer:** This information is for educational purposes only. Drug dosing, contraindications, and interaction profiles can change; always verify current prescribing information using local institutional protocols, package inserts, or reliable clinical decision support tools before prescribing or administering medication.
