Please check your internet connection and try again.
# Mefenamic acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID). It acts primarily by inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis. Its clinical use is strictly limited to short-term therapy (not exceeding 7 days) due to the risk of significant gastrointestinal and renal toxicity.
## Primary Indications
* Primary dysmenorrhea.
* Mild to moderate pain (short-term management).
## Adult Dosing
* **Initial Dose:** 500 mg orally.
* **Maintenance:** 250 mg orally every 6 hours as needed.
* **Duration:** Maximum 7 days of treatment.
## Pediatric Dosing
* **Children ≥ 14 years:** Dosing is the same as adults (500 mg initially, followed by 250 mg every 6 hours).
* **Children < 14 years:** Safety and efficacy have not been established. Use is generally avoided.
## Dose Adjustments
* **Renal Impairment:** Contraindicated in patients with severe renal impairment (CrCl < 30 mL/min). Use with extreme caution in mild-to-moderate impairment; monitor renal function closely.
* **Hepatic Impairment:** Use with caution; monitor for signs of liver dysfunction. In severe hepatic impairment, minimize dose or avoid use.
* **Geriatric:** Use the lowest effective dose for the shortest duration possible due to increased risk of cardiovascular and gastrointestinal events.
## 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 in the setting of coronary artery bypass graft (CABG) surgery.
* Active peptic ulceration or inflammatory bowel disease.
* Severe renal or hepatic impairment.
## Adverse Effects
* **Common:** Abdominal pain, nausea, diarrhea, dyspepsia, dizziness.
* **Serious:** Gastrointestinal bleeding/perforation, myocardial infarction, stroke, peptic ulcer disease, acute renal failure, interstitial nephritis, hepatotoxicity, and fluid retention/hypertension.
## 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 (especially in dehydrated patients).
* **Lithium:** May increase serum lithium concentrations to toxic levels.
* **Methotrexate:** Increased risk of methotrexate toxicity due to reduced clearance.
## Monitoring
* **Renal:** Monitor BUN and Creatinine periodically during prolonged use.
* **GI:** Monitor for signs/symptoms of occult blood loss or GI distress.
* **Cardiovascular:** Monitor blood pressure, particularly in patients with hypertension.
* **Hepatic:** Periodic LFTs if therapy exceeds short-term guidelines.
## Clinical Pearls
* **Treatment Window:** The 7-day limit is non-negotiable due to the high risk of diarrhea and GI ulceration associated with chronic use.
* **Dietary Administration:** Take with food or milk to minimize gastrointestinal upset.
* **CV Warning:** Like all non-aspirin NSAIDs, mefenamic acid carries a boxed warning for increased risk of serious cardiovascular thrombotic events.
* **Cross-reactivity:** Patients with "aspirin-exacerbated respiratory disease" (AERD) should avoid all NSAIDs, including mefenamic acid.
***
**Educational Disclaimer:** This information is for educational purposes and does not substitute for professional medical judgment. Always verify current prescribing information, institutional protocols, and patient-specific factors before administration.
