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# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID) that exhibits analgesic, anti-inflammatory, and antipyretic properties. Like other NSAIDs, it inhibits cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Treatment of mild to moderate pain.
* Treatment of primary dysmenorrhea.
## Adult Dosing
* **Initial Dose:** 500 mg orally once.
* **Maintenance Dose:** 250 mg orally every 6 hours as needed.
* **Maximum Duration:** Do not exceed 7 days of treatment.
## Pediatric Dosing
* **Adolescents (≥14 years):** Dosage is identical to adult dosing.
* **Children (<14 years):** Efficacy and safety have not been established. Avoid use unless instructed by a specialist under specific institutional protocol.
## Dose Adjustments
* **Renal Impairment:** Avoid use in patients with severe renal impairment (CrCl <30 mL/min). Use with caution and monitor closely in mild to moderate impairment.
* **Hepatic Impairment:** Use with caution. Consider lower doses or alternative agents if liver function is impaired.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs (including aspirin-induced asthma/urticaria).
* Active peptic ulceration or inflammatory bowel disease.
* History of GI bleeding or perforation related to NSAID therapy.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Severe renal, hepatic, or cardiac failure.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea (may be severe), abdominal pain, dyspepsia.
* **Serious:** GI ulceration or hemorrhage, hypertension, fluid retention/edema, myocardial infarction, stroke, renal toxicity, skin reactions (Stevens-Johnson syndrome), and blood dyscrasias.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding; monitor INR closely.
* **Antiplatelets/SSRIs:** Increased risk of GI bleeding.
* **Lithium/Methotrexate:** May increase serum levels/toxicity due to reduced renal clearance.
* **Diuretics/ACE Inhibitors/ARBs:** Reduced antihypertensive effect; increased risk of acute kidney injury.
## Monitoring
* Monitor hemoglobin/hematocrit and fecal occult blood if long-term therapy is anticipated (though not recommended).
* Monitor serum creatinine and blood pressure in patients with pre-existing renal or cardiovascular disease.
* Assess for signs of GI irritation or hypersensitivity.
## Clinical Pearls
* **GI Caution:** Mefenamic acid is notorious for inducing diarrhea; if diarrhea occurs, the drug should be discontinued promptly.
* **Duration:** Strict adherence to the 7-day maximum duration is mandatory due to the significant risk of GI and renal adverse effects.
* **Pregnancy/Lactation:** Avoid use, especially in the third trimester (risk of premature closure of ductus arteriosus).
* **Administration:** Take with food or milk to minimize gastrointestinal upset.
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**Educational Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Verify all dosages, contraindications, and drug interactions against current institutional protocols or the official product monograph (FDA/EMA labeling) before prescribing or administering medication. Consultation with a specialist is required for patients with complex comorbidities.
