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# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID). It exerts its effects by inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, leading to reduced prostaglandin synthesis. It possesses analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Primary dysmenorrhea.
* Mild to moderate pain (short-term therapy, typically ≤7 days).
## Adult Dosing
* **Dysmenorrhea/Mild to Moderate Pain:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum Dose:** Do not exceed 1,500 mg/day. Limit duration of treatment to no more than 7 days.
## Pediatric Dosing
* **Children ≥14 years:** Dosing is identical to adult dosing (500 mg initially, then 250 mg every 6 hours).
* **Children <14 years:** Safety and efficacy have not been established. Use is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Avoid or use with extreme caution in cases of severe renal impairment (CrCl <30 mL/min).
* **Hepatic Impairment:** Use with caution; monitor for signs of liver dysfunction. Dose reduction may be required.
## 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.
* Severe heart failure.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
## Adverse Effects
* **Common:** Nausea, abdominal pain, diarrhea, dyspepsia.
* **Serious:** GI ulceration/perforation, increased risk of cardiovascular thrombotic events (myocardial infarction, stroke), hypertension, fluid retention, renal impairment, and blood dyscrasias.
## Key Drug Interactions
* **Anticoagulants/Antiplatelets (e.g., Warfarin, SSRIs):** Increased risk of bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive efficacy and increased risk of acute renal failure.
* **Lithium:** May increase serum levels and risk of toxicity.
* **Methotrexate:** May increase the risk of methotrexate toxicity.
## Monitoring
* Monitor hemoglobin/hematocrit periodically during long-term therapy (though rarely indicated for short-term use).
* Monitor renal function (creatinine, BUN) and blood pressure.
* Observe for signs or symptoms of GI toxicity (e.g., black tarry stools, epigastric pain).
## Clinical Pearls
* **Food:** Administer with food or milk to minimize gastrointestinal upset.
* **Short-term only:** Due to the risk of hemolytic anemia and hepatotoxicity with chronic use, clinical guidelines strongly recommend limiting treatment to 7 days or less.
* **Cross-reactivity:** Patients allergic to aspirin or other NSAIDs are likely to be allergic to mefenamic acid.
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**Educational Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Consult current institutional protocols, prescribing leaflets, and clinical drug databases (e.g., Lexicomp, Micromedex) before prescribing or administering medication.
