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# Mefenamic Acid ## Overview Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the anthranilic acid derivative class. It functions by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis. ## Primary Indications * Short-term management of mild to moderate pain. * Management of primary dysmenorrhea. ## Adult Dosing * **Pain:** 500 mg every 6 hours as needed. Maximum dose: 1500 mg in 24 hours. * **Dysmenorrhea:** 500 mg every 6 hours as needed, starting with the onset of pain or bleeding. Maximum dose: 1500 mg in 24 hours. Treatment should not exceed 7 days. ## Pediatric Dosing The safety and efficacy of mefenamic acid have not been established in pediatric patients under 14 years of age. ## Dose Adjustments No specific dose adjustments are recommended for renal or hepatic impairment based on available data, but caution is advised. Mefenamic acid is generally not recommended in patients with severe renal or hepatic disease. ## Contraindications * Known hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation. * History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs. * Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery. ## Adverse Effects Common adverse effects include: diarrhea, nausea, vomiting, abdominal pain, dyspepsia, constipation, headache, dizziness, rash, and rash. Serious adverse effects include: gastrointestinal bleeding, ulceration, perforation, cardiovascular thrombotic events (myocardial infarction, stroke), renal toxicity, hepatic toxicity, and hypersensitivity reactions. ## Key Drug Interactions * **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. * **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding. * **SSRIs (e.g., fluoxetine, sertraline):** Increased risk of bleeding. * **Diuretics, ACE inhibitors, ARBs:** May reduce antihypertensive effect and increase risk of renal impairment. * **Lithium:** Increased lithium levels and risk of toxicity. * **Methotrexate:** Increased methotrexate levels and risk of toxicity. ## Monitoring * Monitor for signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis). * Monitor for signs and symptoms of cardiovascular events. * Monitor renal function (e.g., BUN, creatinine) and liver function (e.g., AST, ALT), especially in patients with pre-existing conditions or on long-term therapy. * Monitor for signs of hypersensitivity reactions. ## Clinical Pearls * Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset. * Due to the potential for diarrhea, use beyond 7 days is generally not recommended. * Patients should be advised to avoid concurrent use of other NSAIDs. *** *This information is intended for clinical use and does not substitute for professional medical advice. Always verify current prescribing information and guidelines before initiating or modifying therapy.*