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# Mefenamic Acid ## Overview Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) from the fenamate class. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis. ## Primary Indications * Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea). * Relief of fever. ## Adult Dosing * **Pain:** 500 mg every 6 hours as needed. Do not exceed 4000 mg per day. Treatment should not exceed 7 days. * **Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain or bleeding. ## Pediatric Dosing * **Pain and Fever:** Generally not recommended for children younger than 14 years due to lack of established safety and efficacy data. For children 14 years and older, use adult dosing. ## Dose Adjustments * **Renal Impairment:** Use with caution. Data is limited; dose reduction may be necessary based on renal function. * **Hepatic Impairment:** Use with caution. Data is limited; dose reduction may be necessary based on hepatic function. ## Contraindications * Hypersensitivity to mefenamic acid or other NSAIDs. * 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. * Active gastrointestinal (GI) bleeding or history of recurrent GI ulceration or bleeding. * Severe renal or hepatic impairment. * Third trimester of pregnancy. ## Adverse Effects Common adverse effects include nausea, vomiting, diarrhea, abdominal pain, constipation, and dizziness. Serious adverse effects include GI bleeding, ulceration, perforation, cardiovascular thrombotic events (myocardial infarction, stroke), renal failure, hepatic failure, and hypersensitivity reactions. ## Key Drug Interactions * **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. * **Corticosteroids:** Increased risk of GI ulceration and bleeding. * **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of bleeding. * **Lithium:** Increased lithium levels and toxicity. * **Methotrexate:** Increased methotrexate toxicity. * **Diuretics and Antihypertensives:** May reduce efficacy and increase risk of renal toxicity. ## Monitoring * Monitor for signs and symptoms of GI bleeding and ulceration (e.g., melena, hematemesis). * Monitor renal and hepatic function, especially in patients with pre-existing impairment or those on long-term therapy. * Monitor for signs of cardiovascular events. * Assess for efficacy of pain or fever relief. ## Clinical Pearls * Mefenamic acid has a relatively short half-life, requiring frequent dosing. * It is generally recommended for short-term use only. * Advise patients to take with food or milk to minimize GI upset. * Discontinue immediately if signs of hypersensitivity or significant adverse effects occur. --- *This information is intended for healthcare professionals. Always verify current prescribing information and consult relevant guidelines before making clinical decisions.*