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# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative NSAID with analgesic, anti-inflammatory, and antipyretic properties. It acts primarily by inhibiting prostaglandin synthesis via cyclooxygenase (COX-1 and COX-2) inhibition. It is intended for short-term use (typically ≤7 days).
## Primary Indications
* Mild to moderate pain.
* Primary dysmenorrhea.
## Adult Dosing
* **Initial Dose:** 500 mg orally.
* **Maintenance Dose:** 250 mg orally every 6 hours as needed.
* **Maximum Duration:** Do not exceed 7 days of therapy.
## Pediatric Dosing
* **Children ≥14 years:** Use adult dosing.
* **Children <14 years:** Safety and efficacy have not been established; use is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Avoid in patients with severe renal impairment (CrCl <30 mL/min). Use with caution in mild-to-moderate impairment; monitor renal function closely.
* **Hepatic Impairment:** Use with caution. Consider dose reduction if necessary; avoid in severe hepatic dysfunction.
## Contraindications
* Known hypersensitivity (including aspirin-induced asthma or urticaria).
* Active peptic ulceration or inflammatory bowel disease.
* History of GI bleeding or perforation related to prior NSAID therapy.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Severe renal, hepatic, or cardiac failure.
## Adverse Effects
* **Gastrointestinal:** Nausea, vomiting, diarrhea (frequent), abdominal pain, GI ulceration/bleeding.
* **Central Nervous System:** Headache, dizziness, nervousness.
* **Renal:** Fluid retention, edema, risk of acute kidney injury (AKI).
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Cardiovascular:** Increased risk of thrombotic events, myocardial infarction, and stroke (boxed warning).
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding.
* **Antiplatelet agents / SSRIs:** Increased risk of GI bleeding.
* **ACE Inhibitors / ARBs / Diuretics:** Reduced antihypertensive effect and increased risk of nephrotoxicity.
* **Lithium / Methotrexate:** Increased serum concentrations and toxicity risk due to decreased renal clearance.
## Monitoring
* **Baseline/Intermittent:** CBC, renal function (SCr, BUN), and LFTs.
* **Ongoing:** Monitor for symptoms of GI bleeding (occult blood, tarry stools), blood pressure elevation, and signs of edema.
## Clinical Pearls
* **GI Sensitivity:** Use with food or milk to minimize GI upset.
* **Diarrhea:** Mefenamic acid is known to cause dose-related diarrhea more frequently than other NSAIDs; discontinue if diarrhea occurs.
* **CV Risk:** Use the lowest effective dose for the shortest duration possible, especially in patients with cardiovascular risk factors.
* **Self-Limitation:** Due to toxicity potential, this agent is not intended for the management of chronic pain conditions like arthritis.
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**Educational Disclaimer:** This information is for educational purposes only. Always consult the most recent product labeling (Package Insert) or institutional protocols before prescribing or administering medication. Clinical practices may vary by region and individual patient acuity.
