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# Mefenamic Acid ## Overview Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It exhibits analgesic, anti-inflammatory, and antipyretic properties through the inhibition of 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 8 hours as needed. * **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed. * **Maximum Daily Dose:** 1500 mg. Treatment duration should not exceed 7 days. ## Pediatric Dosing Mefenamic acid is generally not recommended for use in children younger than 14 years due to lack of established safety and efficacy data. Some sources suggest doses for children 6 months and older, but this requires careful consideration and close monitoring. ## Dose Adjustments No specific dose adjustments are routinely required for hepatic or renal impairment. However, caution is advised in patients with severe renal or hepatic dysfunction, and the lowest effective dose should be used. ## Contraindications * Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs. * History of bronchospasm, asthma, rhinitis, or urticaria induced by aspirin or other NSAIDs. * Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery. * Active peptic ulceration or history of recurrent gastrointestinal (GI) bleeding. * Severe renal, hepatic, or cardiac impairment. * Third trimester of pregnancy. ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, rash, dizziness, headache. * **Serious:** Severe GI bleeding and ulceration, cardiovascular thrombotic events (MI, stroke), renal failure, hepatic failure, hypersensitivity reactions, Stevens-Johnson syndrome, toxic epidermal necrolysis, bronchospasm, anemia. ## Key Drug Interactions * **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. * **Corticosteroids:** Increased risk of GI ulceration and bleeding. * **Other NSAIDs, including aspirin:** Increased risk of GI adverse effects and bleeding. * **SSRIs/SNRIs:** Increased risk of GI bleeding. * **ACE inhibitors, ARBs, Beta-blockers:** Reduced antihypertensive effect and increased risk of renal impairment. * **Diuretics:** Reduced diuretic effect and increased risk of renal impairment. * **Lithium:** Increased lithium levels and toxicity. * **Methotrexate:** Increased methotrexate levels and toxicity. ## Monitoring * Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis). * Monitor for signs of cardiovascular events (e.g., chest pain, shortness of breath). * Assess renal function (BUN, creatinine) and liver function (AST, ALT) periodically, especially in patients with pre-existing impairment or those on long-term therapy. * Monitor blood pressure. ## Clinical Pearls * Mefenamic acid should be taken with food or milk to minimize GI upset. * It is intended for short-term use only (typically no more than 7 days). * Due to the potential for serious GI and cardiovascular risks, use the lowest effective dose for the shortest duration necessary. * Patients with a history of asthma, especially those with aspirin sensitivity, should use this medication with extreme caution or avoid it altogether. *** *This information is intended for educational purposes and does not substitute for professional medical advice. Always consult with a qualified healthcare provider to determine the appropriateness of any medication for a specific condition and to review the most current prescribing information.*