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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It exerts analgesic and anti-inflammatory effects 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.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* Maximum duration of use is typically 7 days for pain.
## Pediatric Dosing
Mefenamic acid is **not recommended** for use in children under 14 years of age due to a lack of established safety and efficacy.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary; however, specific guidelines are not well-established. Avoid in severe renal impairment.
* **Hepatic Impairment:** Use with caution. Monitor liver function closely. Avoid in severe hepatic impairment.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, 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.
* Inflammatory bowel disease.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include nausea, vomiting, diarrhea, abdominal pain, dyspepsia, and headache. Serious adverse effects can include gastrointestinal bleeding, ulceration, perforation, cardiovascular thrombotic events, renal impairment, hepatic dysfunction, and hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **ACE inhibitors, Angiotensin II Receptor Blockers (ARBs), diuretics:** Increased risk of renal impairment and reduced antihypertensive effect.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate levels and risk of toxicity.
* **Other NSAIDs (including aspirin):** Increased risk of adverse effects, particularly gastrointestinal bleeding.
## Monitoring
* **Gastrointestinal symptoms:** Monitor for signs and symptoms of bleeding or ulceration.
* **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 potential increases.
## Clinical Pearls
* Administer with food or milk to minimize gastrointestinal upset.
* Limit use to the shortest effective duration to minimize risks.
* Consider risks versus benefits, especially in elderly patients or those with cardiovascular disease, renal impairment, or a history of gastrointestinal issues.
* Ensure patients are aware of the potential for serious cardiovascular and gastrointestinal events.
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**Disclaimer:** This information is intended for healthcare professionals and should not replace a thorough review of the most current prescribing information, institutional protocols, and individual patient assessment. Always verify current drug information before making clinical decisions.
