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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It exhibits analgesic, anti-inflammatory, and antipyretic properties through the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term relief of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg as the first dose, followed by 250 mg every 6 hours as needed.
* **Maximum Daily Dose:** Generally not to exceed 1500 mg per day for short-term use.
## Pediatric Dosing
Mefenamic acid is generally **not recommended** for use in children under 14 years of age due to limited data and potential for toxicity.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Reduce dose and monitor renal function closely, especially in patients with pre-existing renal disease.
* **Hepatic Impairment:** Use with caution. Reduce dose and monitor liver function.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of gastrointestinal (GI) bleeding or perforation related to previous NSAID use.
* Active peptic ulceration or history of recurrent peptic ulceration.
* Severe heart failure, renal failure, or hepatic failure.
* Treatment of perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
## Adverse Effects
Common adverse effects include diarrhea, nausea, vomiting, abdominal pain, and rash. Serious GI effects (bleeding, ulceration, perforation) can occur. Other potential serious adverse effects include cardiovascular thrombotic events, renal and hepatic toxicity, hypersensitivity reactions, and exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of GI adverse effects and potential for reduced cardioprotective effect of aspirin.
* **Diuretics, ACE inhibitors, ARBs:** Reduced antihypertensive efficacy and increased risk of renal impairment.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased methotrexate levels and toxicity.
## Monitoring
* **GI symptoms:** Monitor for signs and symptoms of GI bleeding and ulceration.
* **Renal function:** Monitor BUN and creatinine, especially in patients with risk factors for renal impairment.
* **Hepatic function:** Monitor liver enzymes, especially in patients with pre-existing liver disease.
* **Blood pressure:** Monitor for potential increases in blood pressure.
* **Signs of cardiovascular events:** Monitor for new onset or worsening of cardiovascular symptoms.
## Clinical Pearls
* Mefenamic acid should be used at the lowest effective dose for the shortest duration necessary to minimize risks.
* Concurrent use with food or milk may help reduce GI upset.
* Due to the potential for diarrhea, caution is advised in patients with existing GI motility disorders.
* Mefenamic acid's analgesic effect may begin within an hour and can last for up to 4-6 hours.
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*Disclaimer: This information is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider for any health concerns or before making any decisions related to your health or treatment. It is essential to verify current prescribing information and consult official drug compendia for the most up-to-date and comprehensive guidance.*
