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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 and for primary dysmenorrhea. It works by inhibiting prostaglandin synthesis. ## Primary Indications * Mild to moderate pain (e.g., dental pain, post-operative pain) * Primary dysmenorrhea ## Adult Dosing * **Pain:** 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg (though some sources may list up to 2000 mg for short-term use; consult local guidelines). * **Primary Dysmenorrhea:** 500 mg every 6 hours, starting at the onset of pain or bleeding, whichever occurs first. Duration typically 2-3 days. ## Pediatric Dosing Mefenamic acid is generally not recommended for children under 14 years of age due to limited data and potential for adverse effects. For children 14 years and older, dosing is the same as adults. ## Dose Adjustments * **Renal Impairment:** Use with caution. Significant renal impairment is a contraindication. * **Hepatic Impairment:** Use with caution. ## Contraindications * Known hypersensitivity to mefenamic acid or other NSAIDs. * History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs. * Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery. * Active gastrointestinal bleeding or ulceration. * Severe renal or hepatic impairment. * Third trimester of pregnancy. ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation. * **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal failure; hepatic dysfunction; cardiovascular thrombotic events; hypersensitivity reactions; Stevens-Johnson syndrome/toxic epidermal necrolysis. ## Key Drug Interactions * **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. * **Corticosteroids:** Increased risk of gastrointestinal bleeding. * **SSRIs/SNRIs:** Increased risk of gastrointestinal bleeding. * **ACE inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect, increased risk of renal impairment. * **Lithium:** Increased lithium levels. * **Methotrexate:** Increased methotrexate toxicity. ## Monitoring * **Baseline and periodic renal function (creatinine, BUN).** * **Liver function tests (AST, ALT).** * **Hemoglobin/hematocrit** (especially with prolonged use or signs of GI bleeding). * **Signs and symptoms of GI bleeding** (melena, hematemesis, abdominal pain). * **Blood pressure.** ## Clinical Pearls * Mefenamic acid is intended for short-term use only. * Administer with food or milk to minimize gastrointestinal upset. * Avoid concomitant use with other NSAIDs. * Discontinue if signs of renal or hepatic toxicity or gastrointestinal bleeding occur. *** *Disclaimer: This information is intended for healthcare professionals. Always verify current prescribing information and consult with a pharmacist or physician for individualized patient care.*