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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.
* *Note: Treatment duration is restricted to no more than 7 days.*
## Adult Dosing
* **Initial Dose:** 500 mg orally.
* **Maintenance Dose:** 250 mg orally every 6 hours as needed.
* **Maximum Dose:** 1,500 mg per day.
## Pediatric Dosing
* **Children >14 years:** Use adult dosing guidelines (see Adult Dosing).
* **Children <14 years:** Safety and efficacy are not established; use is generally avoided.
## Dose Adjustments
* **Renal Impairment:** Not recommended for use in patients with severe renal impairment (CrCl <30 mL/min). Use with caution in mild-to-moderate impairment; monitor baseline and periodic renal function.
* **Hepatic Impairment:** Avoid in patients with severe hepatic impairment. Reduce doses in patients with mild-to-moderate liver disease.
## 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.
* Coronary artery bypass graft (CABG) surgery (perioperative pain management).
* Severe renal or hepatic failure.
* Third trimester of pregnancy (risk of premature closure of ductus arteriosus).
## Adverse Effects
* **Common:** Abdominal pain, nausea, diarrhea (frequent), dyspepsia, dizziness, headache.
* **Serious:** GI ulceration/bleeding, myocardial infarction, stroke, sodium retention/edema, acute renal failure, interstitial nephritis, exfoliative dermatitis (e.g., Stevens-Johnson Syndrome).
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increases risk of bleeding.
* **Antiplatelets (e.g., Clopidogrel, SSRIs):** Increases risk of GI hemorrhage.
* **ACE Inhibitors/ARBs/Diuretics:** Potentiates nephrotoxicity and reduces antihypertensive efficacy.
* **Lithium/Methotrexate:** Increases plasma concentrations and toxicity risk.
* **Other NSAIDs/Corticosteroids:** Significantly increases risk of GI ulceration.
## Monitoring
* **GI:** Monitor for signs of occult blood loss or symptoms of peptic ulceration.
* **Renal:** Periodic monitoring of serum creatinine, BUN, and electrolytes.
* **Cardiovascular:** Monitor blood pressure; assess for fluid retention.
* **Hepatic:** Monitor liver enzymes if long-term treatment is initiated (though discouraged).
## Clinical Pearls
* **Duration:** Therapy should be limited to 7 days due to the increased risk of potentially severe gastrointestinal and renal adverse effects.
* **Administration:** Take with food or milk to minimize gastrointestinal irritation.
* **Diarrhea:** Diarrhea is a dose-related side effect that occurs more frequently with mefenamic acid than with other NSAIDs; discontinue if severe diarrhea occurs.
* **Cross-reactivity:** Patients allergic to aspirin or other NSAIDs may exhibit cross-sensitivity.
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**Educational Disclaimer:** This information is for educational purposes only. Always consult the most recent product monograph, prescribing information, or local hospital formulary protocols before prescribing or administering medication, as clinical guidelines and safety warnings are subject to change.
