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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 inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, leading to reduced prostaglandin synthesis.
## Primary Indications
* Treatment of primary dysmenorrhea.
* Mild to moderate pain (short-term use, typically ≤7 days).
## Adult Dosing
* **Dysmenorrhea/Pain:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum Dose:** Do not exceed 1,500 mg/day. Limit duration to 7 days.
## Pediatric Dosing
* **Children (≥14 years):** Same as adult dosing.
* **Children (<14 years):** Safety and efficacy have not been established; use is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Not recommended in patients with severe renal impairment (CrCl <30 mL/min). Use with caution in mild-to-moderate impairment.
* **Hepatic Impairment:** Use with caution. Monitor closely for signs of hepatic dysfunction; avoid in severe liver disease.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs (including aspirin-induced asthma or urticaria).
* History of GI bleeding or perforation related to prior NSAID therapy.
* Active peptic ulcer disease or inflammatory bowel disease.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Severe renal or hepatic failure.
## Adverse Effects
* **Gastrointestinal:** Nausea, vomiting, diarrhea (may be severe), abdominal pain, GI ulceration/bleeding.
* **Cardiovascular:** Hypertension, edema, increased risk of MI/stroke (class-wide NSAID warnings).
* **Renal:** Acute renal failure, fluid retention, interstitial nephritis.
* **Hematologic:** Anemia, increased bleeding time.
* **Neurologic:** Dizziness, headache.
## Key Drug Interactions
* **Anticoagulants/Antiplatelets:** Increased risk of bleeding (e.g., warfarin, clopidogrel).
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of nephrotoxicity.
* **Lithium/Methotrexate:** NSAIDs may decrease clearance, increasing risk of toxicity.
* **Other NSAIDs/Corticosteroids:** Increased risk of GI toxicity.
## Monitoring
* **GI:** Monitor for signs of occult bleeding or dyspepsia.
* **Renal:** Periodic monitoring of serum creatinine, BUN, and urine output, especially in high-risk patients.
* **Blood Pressure:** Regular monitoring during therapy.
* **CBC:** Monitor if long-term therapy is contemplated (due to risk of anemia/platelet aggregation inhibition).
## Clinical Pearls
* **GI Sensitivity:** Unlike other NSAIDs, mefenamic acid is frequently associated with diarrhea, which may be dose-related; discontinue if severe diarrhea occurs.
* **Administration:** Take with food or milk to minimize gastrointestinal upset.
* **Duration:** It is strictly indicated for short-term use (≤ 7 days). Chronic use increases risks of serious CV and GI adverse events.
* **Pregnancy:** Avoid in the third trimester (≥30 weeks gestation) due to risk of premature closure of the ductus arteriosus and persistent pulmonary hypertension in the newborn.
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**Disclaimer:** This information is for educational purposes and does not replace professional clinical judgment. Always verify current prescribing information, institutional protocols, and local drug monographs before prescribing or administering medication.
