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# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID). It exerts analgesic, anti-inflammatory, and antipyretic effects primarily through the non-selective inhibition of cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Treatment of mild to moderate pain.
* Primary dysmenorrhea.
* *Note:* Use is generally limited to short-term therapy (≤ 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 daily.
## 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:** 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:** Use with caution; dose reduction may be required. Avoid in severe hepatic impairment.
* **Geriatric:** Use the lowest effective dose for the shortest duration due to increased risk of gastrointestinal (GI) and renal toxicity.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Setting of coronary artery bypass graft (CABG) surgery (perioperative pain management).
* Active GI bleeding or peptic ulcer disease.
* Severe renal or hepatic failure.
## Adverse Effects
* **Common:** Abdominal pain, diarrhea (often dose-related), nausea, dyspepsia, dizziness, and headache.
* **Serious:** GI bleeding/ulceration, cardiovascular events (myocardial infarction, stroke), hypertension, fluid retention/edema, nephrotoxicity, and severe hypersensitivity reactions (e.g., Stevens-Johnson syndrome).
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of major bleeding.
* **Antiplatelets/SSRIs:** Increased risk of GI bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of acute kidney injury.
* **Lithium/Methotrexate:** Potential increase in serum concentrations leading to toxicity.
* **Other NSAIDs:** Increased risk of adverse effects; avoid concomitant use.
## Monitoring
* **Baseline:** CBC, renal function (SCr/BUN), and blood pressure.
* **Ongoing:** Periodic monitoring of renal function, blood pressure, and signs/symptoms of GI bleeding or occult anemia during prolonged use.
## Clinical Pearls
* **GI Sensitivity:** Frequently causes diarrhea; if diarrhea occurs, the dose should be reduced or the drug discontinued.
* **Short Duration:** FDA labeling recommends limiting treatment to no more than 7 days due to the risk of dose-related GI toxicity.
* **Cardiovascular Risk:** Like all non-aspirin NSAIDs, mefenamic acid may increase the risk of serious cardiovascular thrombotic events.
* **Pregnancy:** Avoid in late pregnancy (third trimester) as it may cause 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, contraindications, and interaction profiles may vary based on local guidelines, patient-specific factors, and changing clinical evidence. Always consult the most current prescribing information (e.g., FDA-approved package insert or reliable drug databases like Lexicomp or Micromedex) before prescribing or administering medication.
