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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term management of mild to moderate pain. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term treatment of mild to moderate pain, including menstrual pain (dysmenorrhea).
* Management of rheumatoid arthritis and osteoarthritis (less common due to safety profile).
## Adult Dosing
* **Pain:** 500 mg orally every 6 hours as needed.
* **Dysmenorrhea:** 500 mg orally every 6 hours as needed, starting at the onset of pain and bleeding.
* **Maximum Daily Dose:** 1500 mg. Treatment duration should not exceed 7 days for pain.
## Pediatric Dosing
* **Pain:** 6 months to 12 years: 6.5 mg/kg orally every 6 hours as needed.
* **Maximum Daily Dose:** Not to exceed 1500 mg.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Significant renal impairment may warrant dose reduction or discontinuation. Data is limited, and no specific guidelines are established.
* **Hepatic Impairment:** Use with caution. Monitor liver function tests. Data is limited, and no specific guidelines are established.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, 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 bleeding or history of gastrointestinal bleeding or perforation related to previous NSAID use.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, headache, dizziness.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal failure; hepatic failure; hypersensitivity reactions (including Stevens-Johnson syndrome, toxic epidermal necrolysis); aplastic anemia; hemolytic anemia.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of gastrointestinal bleeding.
* **ACE inhibitors, ARBs, Beta-blockers:** Reduced antihypertensive effect; increased risk of renal impairment.
* **Diuretics:** Reduced diuretic and antihypertensive effect; increased risk of renal impairment.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Gastrointestinal:** Monitor for signs and symptoms of gastrointestinal bleeding, ulceration, and perforation (e.g., black tarry stools, hematemesis).
* **Cardiovascular:** Monitor for signs of thrombotic events (e.g., chest pain, shortness of breath, weakness, slurring of speech).
* **Renal:** Monitor renal function, especially in patients with pre-existing renal disease or those taking concomitant nephrotoxic agents.
* **Hepatic:** Monitor liver function tests, especially in patients with pre-existing liver disease.
* **Hematologic:** Monitor for signs of anemia or other hematologic abnormalities.
## Clinical Pearls
* Mefenamic acid is generally recommended for short-term use only due to its increased risk of gastrointestinal and cardiovascular adverse events compared to some other NSAIDs.
* Its efficacy in dysmenorrhea is well-established, often providing relief within hours of the first dose.
* Avoid concomitant use with other NSAIDs to minimize adverse effects.
* Due to the potential for hemolytic anemia, caution is advised in patients with pre-existing anemia or underlying hematologic conditions.
* The risk of aseptic meningitis has been reported with NSAID use, particularly in patients with systemic lupus erythematosus.
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*Please verify current prescribing information and consult with a healthcare professional before making any treatment decisions.*
