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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) with analgesic, anti-inflammatory, and antipyretic properties. It acts primarily by inhibiting the cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Treatment of primary dysmenorrhea.
* Mild to moderate pain (short-term therapy not exceeding 7 days).
## Adult Dosing
* **Dysmenorrhea/Mild-to-moderate pain:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum duration:** Do not exceed 7 days of treatment.
## Pediatric Dosing
* **Adolescents (≥14 years):** 500 mg initially, followed by 250 mg every 6 hours as needed, for no more than 7 days.
* **Children (<14 years):** Safety and efficacy have not been established.
## Dose Adjustments
* **Renal Impairment:** Avoid use in severe renal impairment (CrCl <30 mL/min). Use with caution in mild-to-moderate impairment.
* **Hepatic Impairment:** Use with caution. If necessary, consider lower doses due to potential for hepatotoxicity.
* **Geriatric:** Use the lowest effective dose for the shortest duration due to increased risk of GI bleeding and cardiovascular events.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs (including aspirin-induced asthma or urticaria).
* History of asthma or allergic-type reactions to aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active peptic ulcer disease or gastrointestinal bleeding.
* Severe renal or hepatic impairment.
## Adverse Effects
* **Gastrointestinal:** Nausea, abdominal pain, diarrhea (common with mefenamic acid), GI ulceration/bleeding.
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, hypertension, and fluid retention.
* **Renal:** Acute renal failure, interstitial nephritis, fluid/electrolyte imbalances.
* **Hematologic:** Anemia, thrombocytopenia, hemolytic anemia (rare, with long-term use).
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding.
* **Antiplatelets/SSRIs:** Increased risk of GI bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of acute kidney injury.
* **Lithium:** May increase serum lithium concentrations to toxic levels.
* **Methotrexate:** May increase serum methotrexate concentrations.
## Monitoring
* **GI:** Monitor for signs/symptoms of GI ulceration or bleeding.
* **Renal/Hepatic:** Periodic monitoring of serum creatinine, BUN, and liver function tests if used beyond short-term therapy.
* **Blood Pressure:** Monitor periodically during treatment.
* **Hematologic:** Monitor for signs of anemia if therapy is prolonged.
## Clinical Pearls
* **Duration:** Therapy is strictly limited to 7 days due to the increased risk of severe diarrhea and hematological toxicity with prolonged use.
* **Administration:** Administer with food or milk to minimize gastrointestinal distress.
* **Diarrhea:** Diarrhea is uniquely associated with mefenamic acid; if severe diarrhea occurs, discontinue the drug.
* **NSAID Class Effect:** Like all NSAIDs, it carries a boxed warning regarding cardiovascular and gastrointestinal risks.
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**Disclaimer:** This information is for educational purposes only. Always verify current prescribing information, contraindications, and dosing protocols via official product monographs or institutional resources before prescribing or administering medication.
