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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, primarily by inhibiting cyclooxygenase (COX-1 and COX-2) enzymes and reducing prostaglandin synthesis. ## Primary Indications * Treatment of primary dysmenorrhea. * Short-term management of mild to moderate pain (typically not exceeding 7 days of therapy). ## Adult Dosing * **Dysmenorrhea/Pain:** 500 mg orally as an initial dose, followed by 250 mg every 6 hours as needed. * **Maximum Dose:** Do not exceed 7 days of continuous therapy. ## Pediatric Dosing * **Children ≥ 14 years:** Use adult dosing regimen. * **Children < 14 years:** Safety and efficacy have not been established; generally not recommended. ## Dose Adjustments * **Renal Impairment:** Avoid in severe renal impairment. Use with caution in mild-to-moderate impairment; close monitoring of renal function is required. * **Hepatic Impairment:** Use with caution; monitor for signs of liver dysfunction. Dose reduction may be prudent. * **Geriatric Patients:** Use the lowest effective dose for the shortest duration due to increased risk of cardiovascular and gastrointestinal adverse events. ## Contraindications * Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs. * History of asthma, urticaria, or allergic-type reactions triggered by aspirin or other NSAIDs. * Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery. * History of GI bleeding or perforation related to previous NSAID therapy. * Active peptic ulcer disease or inflammatory bowel disease. * Severe renal or hepatic failure. ## Adverse Effects * **Common:** Abdominal pain, nausea, diarrhea (can be severe), dizziness, and headache. * **Serious:** GI ulceration/bleeding, myocardial infarction, stroke, fluid retention/edema, hypertension, renal impairment, and severe cutaneous adverse reactions (e.g., SJS/TEN). ## 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 acute kidney injury. * **Lithium/Methotrexate:** Increased plasma concentrations and potential for toxicity. ## Monitoring * **GI:** Monitor for signs of occult or overt GI bleeding. * **Renal/Hepatic:** Periodic monitoring of serum creatinine, BUN, and LFTs in long-term therapy. * **Blood Pressure:** Monitor baseline and periodic BP measurements. * **Cardiovascular:** Monitor for signs of fluid retention or new/worsening heart failure. ## Clinical Pearls * **Duration Limit:** Mefenamic acid is specifically contraindicated for long-term use due to the high risk of GI toxicity and diarrhea. * **Administration:** Take with food or milk to minimize gastrointestinal upset. * **Diarrhea:** Diarrhea is a more common side effect of mefenamic acid compared to other NSAIDs; if it occurs, the drug should be discontinued promptly. *** **Educational Disclaimer:** This information is for educational purposes only and does not replace professional medical judgment. Always verify current prescribing information (e.g., package insert) and local clinical protocols before administering or prescribing this medication.