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# Mefenamic Acid ## Overview Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term relief of mild to moderate pain. It is a member of the fenamate class of NSAIDs. ## Primary Indications * Dysmenorrhea (menstrual pain) * Mild to moderate pain, including dental pain and musculoskeletal pain ## Adult Dosing * **Pain:** 500 mg every 4 to 6 hours as needed. * **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed. * **Maximum Daily Dose:** 1250 mg per day for short-term use. ## Pediatric Dosing Dosing in children under 14 years of age is not well-established and should be approached with caution. If used, a typical starting dose is 6.5 mg/kg every 6 hours. Maximum daily dose is 500 mg. ## Dose Adjustments * **Renal Impairment:** Use with caution. Dose reduction may be necessary, though specific guidelines are lacking. Monitor renal function closely. * **Hepatic Impairment:** Use with caution. Dose reduction may be necessary. Monitor liver function closely. ## Contraindications * Hypersensitivity to mefenamic acid or other NSAIDs. * History of asthma, urticaria, or other allergic-type reactions after taking aspirin or other NSAIDs. * Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery. * Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis). * Renal or hepatic failure. * Third trimester of pregnancy. ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation. * **Serious:** * Gastrointestinal bleeding, ulceration, perforation. * Cardiovascular thrombotic events (myocardial infarction, stroke). * Renal toxicity (e.g., interstitial nephritis, papillary necrosis). * Hepatotoxicity. * Hypersensitivity reactions (including anaphylaxis). * Hematologic effects (anemia, leukopenia). ## Key Drug Interactions * **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. * **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding. * **SSRIs/SNRIs:** Increased risk of gastrointestinal bleeding. * **Diuretics:** Reduced diuretic efficacy; increased risk of renal toxicity. * **ACE Inhibitors/ARBs:** Increased risk of renal impairment. * **Lithium:** Increased serum lithium levels. * **Methotrexate:** Increased risk of methotrexate toxicity. ## Monitoring * **Baseline and periodic assessment of renal function (BUN, creatinine).** * **Baseline and periodic assessment of liver function (ALT, AST).** * **Monitor for signs and symptoms of gastrointestinal bleeding (melena, hematemesis).** * **Monitor for signs and symptoms of cardiovascular events.** * **Monitor for signs of hypersensitivity reactions.** * **Monitor complete blood count (CBC) if prolonged therapy is anticipated.** ## Clinical Pearls * Mefenamic acid is generally recommended for short-term use only, typically not exceeding 7 days for pain relief. * It should be taken with food or milk to minimize gastrointestinal upset. * Due to potential for CNS effects, caution patients about operating machinery or driving until they know how the drug affects them. * Risk of serious cardiovascular thrombotic events is increased with dose and duration of use. * Risk of serious gastrointestinal bleeding is increased in the elderly and with concurrent use of corticosteroids or anticoagulants. *** **Disclaimer:** This information is intended for healthcare professionals. Always verify current prescribing information and consult with the most up-to-date resources before making clinical decisions.