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# Mefenamic acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID). It exerts anti-inflammatory, analgesic, and antipyretic effects primarily by inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, leading to reduced prostaglandin synthesis. It is generally intended for short-term use (≤7 days).
## Primary Indications
* Treatment of mild to moderate pain.
* Treatment of primary dysmenorrhea.
## Adult Dosing
* **Pain/Dysmenorrhea:** 500 mg orally initially, followed by 250 mg every 6 hours as needed.
* **Maximum Duration:** Do not exceed 7 days of therapy.
## Pediatric Dosing
* **Adolescents (≥14 years):** Follow adult dosing schedule.
* **Children (<14 years):** Safety and efficacy have not been established. Use is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Avoid in severe renal impairment (CrCl <30 mL/min).
* **Hepatic Impairment:** Use with caution; monitor for signs of hepatic toxicity. Dose reduction may be required.
* **Geriatric:** Use the lowest effective dose for the shortest duration possible due to increased risk of GI, cardiovascular, and renal adverse effects.
## Contraindications
* Hypersensitivity to mefenamic acid or any component of the formulation.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* History of GI bleeding or perforation related to previous NSAID therapy.
* Active peptic ulcer disease or inflammatory bowel disease.
* Severe renal or hepatic impairment.
## Adverse Effects
* **Gastrointestinal:** Nausea, vomiting, diarrhea (may be severe), abdominal pain, dyspepsia, risk of GI ulceration/bleeding.
* **Renal:** Fluid retention, edema, acute renal failure, interstitial nephritis.
* **Cardiovascular:** Hypertension, increased risk of serious thrombotic events (myocardial infarction, stroke).
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Dermatologic:** Rash, pruritus, rare cases of Stevens-Johnson syndrome/TEN.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding; monitor INR closely.
* **Antiplatelet Agents/SSRIs:** Increased risk of GI bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium:** May increase serum lithium concentrations to toxic levels.
* **Methotrexate:** Increased risk of methotrexate toxicity due to reduced renal clearance.
## Monitoring
* Baseline and periodic assessment of renal function (BUN/SCr).
* Monitor hemoglobin/hematocrit if long-term therapy is anticipated.
* Monitor blood pressure periodically.
* Observe for signs or symptoms of GI bleeding (tarry stools, hematemesis).
## Clinical Pearls
* **GI Irritation:** Take with food or milk to minimize gastrointestinal distress; however, this may delay absorption.
* **Duration Limit:** Due to the risk of significant diarrhea and GI toxicity, treatment beyond 7 days is rarely recommended.
* **Cardiovascular Warning:** Like all NSAIDs, mefenamic acid may increase the risk of serious cardiovascular thrombotic events.
* **Diarrhea Protocol:** If severe diarrhea occurs, the drug should be discontinued promptly.
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**Disclaimer:** This information is for educational purposes only. Clinical practice guidelines and prescribing information can change. Always verify current prescribing information, package inserts, and local institutional protocols before administration. Consult a qualified healthcare professional for clinical decision-making.
