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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties, primarily by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose: 1500 mg.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting with the onset of pain or bleeding, whichever comes first. Maximum daily dose: 1500 mg.
* **Duration of Use:** Typically recommended for short-term use, not exceeding 7 days.
## Pediatric Dosing
* **Age:** Approved for patients 14 years of age and older.
* **Dosing:** Same as adult dosing (500 mg every 6 hours as needed, max 1500 mg/day).
* **Under 14 years:** Dosing is not established.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but dose reduction may be considered in severe impairment.
* **Hepatic Impairment:** Use with caution. Data is limited, but dose reduction may be considered in severe impairment.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal toxicity. Lower doses and careful monitoring are recommended.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* 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.
* Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis).
* Third trimester of pregnancy.
## Adverse Effects
**Common:**
* Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia.
* Central Nervous System: Dizziness, headache, drowsiness.
**Serious:**
* Cardiovascular: Increased risk of myocardial infarction, stroke, and heart failure.
* Gastrointestinal: Serious bleeding, ulceration, and perforation.
* Renal: Renal dysfunction, interstitial nephritis, papillary necrosis.
* Hepatic: Hepatotoxicity, elevated liver enzymes.
* Hematologic: Anemia, leukopenia, thrombocytopenia.
* Dermatologic: Serious skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis).
* Hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of gastrointestinal bleeding.
* **Aspirin:** Concomitant use may reduce the cardioprotective effects of low-dose aspirin and increase the risk of gastrointestinal bleeding.
* **Diuretics and ACE inhibitors:** May reduce antihypertensive effects and increase risk of renal impairment.
* **Lithium:** Mefenamic acid may increase serum lithium levels.
## Monitoring
* **For prolonged use:** Monitor renal function (BUN, creatinine), liver function tests (AST, ALT), and complete blood count (CBC).
* **Gastrointestinal symptoms:** Assess for signs and symptoms of bleeding (e.g., melena, hematemesis).
* **Cardiovascular risk factors:** Assess and monitor for signs of cardiovascular events.
## Clinical Pearls
* Mefenamic acid is generally reserved for short-term pain management due to its GI and renal toxicity profile.
* It should be taken with food or milk to minimize gastrointestinal upset.
* Due to potential drowsiness, caution patients regarding driving or operating machinery.
* Not recommended for use in patients with significant renal or hepatic impairment.
* Lowest effective dose for the shortest duration necessary should be used.
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*Please consult the most current prescribing information for complete details and to verify this information.*
