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# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID). It exhibits analgesic, anti-inflammatory, and antipyretic properties via the inhibition of prostaglandin synthesis through non-selective inhibition of cyclooxygenase (COX-1 and COX-2) enzymes.
## 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
* **Pain/Dysmenorrhea:** 500 mg orally as an initial dose, followed by 250 mg every 6 hours as needed.
* **Maximum Dose:** Do not exceed 1,500 mg per day.
## Pediatric Dosing
* **Children ≥14 years:** Use adult dosing regimens.
* **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 and monitor closely in mild to moderate impairment.
* **Hepatic Impairment:** Use with caution. Consider dose reduction in patients with hepatic insufficiency; avoidance is recommended in severe hepatic disease (may increase risk of hepatotoxicity).
* **Geriatric:** Initiate at the lowest effective dose; increased risk of serious gastrointestinal and cardiovascular adverse events.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Treatment of perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active peptic ulcer disease or gastrointestinal bleeding.
* Severe renal or hepatic failure.
## Adverse Effects
* **Common:** Abdominal pain, dyspepsia, nausea, diarrhea, dizziness, headache.
* **Serious:** Gastrointestinal ulceration/perforation, myocardial infarction, stroke, new-onset or exacerbated hypertension, fluid retention/edema, acute renal failure, hepatic toxicity, exfoliative dermatitis, Stevens-Johnson syndrome.
## 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 renal impairment (nephrotoxicity).
* **Lithium/Methotrexate:** Decreased renal clearance, leading to potential toxicity of these agents.
## Monitoring
* **Baseline/Intermittent:** CBC (for anemia/bleeding), renal function (BUN/SCr), and liver function tests.
* **Ongoing:** Blood pressure monitoring, assessment for signs of GI bleeding, and cardiovascular symptoms (e.g., chest pain, shortness of breath).
## Clinical Pearls
* **Duration:** Limit use to the shortest duration necessary to control symptoms to minimize cardiovascular and gastrointestinal risks.
* **Administration:** Take with food or milk to decrease gastrointestinal irritation.
* **Cross-reactivity:** Patients sensitive to one NSAID should be assumed potentially sensitive to all NSAIDs.
* **Pregnancy:** Avoid after 30 weeks gestation due to the risk of premature closure of the ductus arteriosus.
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**Educational Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Dosing and clinical practices may vary based on local protocols and institutional guidelines. Always verify current prescribing information, contraindications, and drug interactions via official resources (e.g., electronic health record, package insert, or Lexicomp/Micromedex) before prescribing or administering medication.
