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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties by non-selectively inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Treatment of mild-to-moderate pain.
* Primary dysmenorrhea.
* *Note: Use is generally limited to short-term therapy (not exceeding 7 days).*
## Adult Dosing
* **Initial Dose:** 500 mg orally.
* **Maintenance Dose:** 250 mg orally every 6 hours as needed.
* **Maximum Duration:** 1 week.
## Pediatric Dosing
* **Children ≥ 14 years:** Same as adult dosing.
* **Children < 14 years:** Safety and efficacy have not been established. Use is generally not recommended in this population.
## 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:** Avoid in severe hepatic impairment. Reduce dose if necessary in mild-to-moderate cases; monitor for signs of hepatotoxicity.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs/aspirin (risk of bronchospasm or anaphylaxis).
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Treatment of peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active peptic ulcer disease or inflammatory bowel disease (IBD).
## Adverse Effects
* **Common:** Abdominal pain, nausea, diarrhea, dyspepsia, dizziness, nervousness, headache.
* **Serious:** Cardiovascular thrombotic events, myocardial infarction, stroke, gastrointestinal bleeding, ulceration/perforation, acute renal failure, hepatotoxicity, Stevens-Johnson syndrome, and fluid retention.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding due to effects on platelet function and gastric mucosa.
* **Antiplatelet Agents/SSRIs:** Increased risk of gastrointestinal bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive efficacy and increased risk of renal impairment.
* **Lithium/Methotrexate:** Decreased renal clearance leading to potential toxicity.
## Monitoring
* **Renal:** Monitor serum creatinine and BUN in patients with risk factors.
* **Hepatic:** Monitor LFTs if signs of liver dysfunction appear.
* **Gastrointestinal:** Monitor for signs or symptoms of GI bleeding (e.g., black/tarry stools, hematemesis).
* **Cardiovascular:** Monitor for symptoms of fluid retention, edema, or hypertension.
## Clinical Pearls
* **Counseling:** Take with food or milk to minimize gastrointestinal upset.
* **Short Term:** Due to the risk of hemolytic anemia and other toxicities with chronic use, mefenamic acid is strictly intended for short-term management.
* **NSAID Class Caution:** Avoid concurrent use of multiple NSAIDs due to increased risk of toxicity without additional therapeutic benefit.
* **Specific Risk:** Patients with a history of diarrhea may find the GI side effect profile of mefenamic acid specifically problematic.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice guidelines vary by institution and region. Always consult the most current product monograph, drug formulary, or reliable clinical decision-support databases (e.g., Lexicomp, UpToDate) before prescribing or administering any medication.
