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# Mefenamic Acid ## Overview Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term treatment of mild to moderate pain. ## Primary Indications * Pain associated with osteoarthritis and rheumatoid arthritis. * Primary dysmenorrhea. ## Adult Dosing * **Pain:** 500 mg every 6 hours as needed. * **Dysmenorrhea:** 500 mg every 4-6 hours as needed, not to exceed 4 days. * **Maximum daily dose:** 1500 mg. Duration of treatment should generally not exceed 7 days. ## Pediatric Dosing * **14 years and older:** Same as adult dosing. * **Under 14 years:** Safety and efficacy have not been established. ## Dose Adjustments * **Renal Impairment:** Use with caution. Dose reduction may be necessary, though specific guidelines are not well-established. * **Hepatic Impairment:** Use with caution. Dose reduction may be necessary, though specific guidelines are not well-established. ## Contraindications * Hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation. * History of bronchospasm, asthma, rhinitis, urticaria, or other allergic-type reactions after taking aspirin or other NSAIDs. * Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery. ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, headache. * **Serious:** Cardiovascular thrombotic events (myocardial infarction, stroke), gastrointestinal bleeding, ulceration, perforation, renal toxicity, hepatic toxicity, hypersensitivity reactions, Stevens-Johnson syndrome, toxic epidermal necrolysis. ## Key Drug Interactions * **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely. * **Corticosteroids:** Increased risk of GI ulceration and bleeding. * **Other NSAIDs (including aspirin):** Increased risk of adverse effects, particularly GI bleeding. * **Diuretics, ACE inhibitors, ARBs:** May reduce antihypertensive effect and increase risk of renal impairment. * **Lithium:** Increased lithium levels and toxicity. * **Methotrexate:** Increased methotrexate levels and toxicity. ## Monitoring * Signs and symptoms of GI bleeding or ulceration. * Renal function (BUN, creatinine). * Liver function tests (ALT, AST). * Blood pressure. * For patients with cardiovascular risk factors, consider risk of thrombotic events. ## Clinical Pearls * Administer with food or milk to minimize GI upset. * Use the lowest effective dose for the shortest duration necessary. * Avoid concomitant use with other NSAIDs. * Discontinue if severe adverse reactions occur. *** This information is intended for healthcare professionals. Please refer to the most current prescribing information and local protocols for definitive guidance.