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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 and for the treatment of primary dysmenorrhea.
## Primary Indications
* Pain (mild to moderate)
* Primary dysmenorrhea
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Primary Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum dose:** 1500 mg/day. Treatment duration typically limited to 7 days.
## Pediatric Dosing
* Mefenamic acid is **not recommended** for pediatric patients under 14 years of age due to lack of established efficacy and safety.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustments are established, but dose reduction may be considered in severe impairment.
* **Hepatic Impairment:** Use with caution. No specific dose adjustments are established, but dose reduction may be considered in severe impairment.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* History of NSAID-induced bronchospasm, urticaria, or allergic-type reactions.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Known history of inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis).
* Active peptic ulceration or gastrointestinal bleeding.
* Severe renal or hepatic impairment.
* Severe heart failure.
* Pregnancy (third trimester).
## Adverse Effects
* **Gastrointestinal:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, gastrointestinal bleeding, perforation.
* **Central Nervous System:** Dizziness, headache, drowsiness.
* **Renal:** Renal failure, interstitial nephritis, papillary necrosis.
* **Hepatic:** Hepatotoxicity, elevated liver enzymes.
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Dermatologic:** Rash, pruritus, Stevens-Johnson syndrome, toxic epidermal necrolysis.
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, hypertension, edema.
## 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) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **Lithium:** Mefenamic acid can decrease renal clearance of lithium, leading to increased lithium levels and toxicity. Monitor lithium levels.
* **Methotrexate:** Mefenamic acid can increase methotrexate levels, potentially leading to toxicity.
* **Diuretics and Antihypertensives:** NSAIDs may blunt the effects of these drugs and increase the risk of renal impairment.
## Monitoring
* **Gastrointestinal:** Monitor for signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis).
* **Renal function:** Monitor BUN and creatinine, especially in patients with pre-existing renal disease or those taking concomitant nephrotoxic agents.
* **Hepatic function:** Monitor liver enzymes, especially in patients with pre-existing liver disease.
* **Blood pressure:** Monitor for hypertension.
* **Signs of hypersensitivity:** Discontinue if rash or other allergic symptoms occur.
## Clinical Pearls
* Limit mefenamic acid use to the shortest duration necessary to control symptoms.
* Administer with food or milk to reduce gastrointestinal upset.
* Avoid concomitant use with other NSAIDs, including aspirin, due to increased risk of adverse effects.
* Consider the cardiovascular and renal risks associated with NSAID use, especially in elderly patients or those with risk factors.
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**Disclaimer:** This information is intended for educational purposes and does not substitute for professional medical advice. Always verify current prescribing information and consult with a qualified healthcare provider before making any decisions about drug therapy.
