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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It is used for the short-term treatment of mild to moderate pain.
## Primary Indications
* Pain, including menstrual pain (dysmenorrhea)
* Pain associated with dental procedures
* Other mild to moderate pain
## Adult Dosing
* **Initial dose:** 500 mg orally every 6 hours as needed.
* **Maximum daily dose:** 1500 mg orally per day.
* Treatment should not exceed 7 days.
## Pediatric Dosing
* **Children 14 years and older:** Same as adult dosing.
* **Children younger than 14 years:** Dosing is not established. Mefenamic acid is generally not recommended in children under 14 years due to lack of established safety and efficacy data.
## Dose Adjustments
* **Renal impairment:** Use with caution. In severe renal impairment, dose reduction may be necessary; however, specific guidelines are not well-defined. Monitor for signs of renal toxicity.
* **Hepatic impairment:** Use with caution. Patients with hepatic impairment may require lower doses. Monitor liver function tests.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, asthma, 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 ulcer disease.
* Severe renal or hepatic impairment.
* Pregnancy in the third trimester.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, constipation, rash, dizziness, headache.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (myocardial infarction, stroke); renal failure; hepatic failure; hypersensitivity reactions; bronchospasm; fluid retention and edema.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of gastrointestinal adverse effects.
* **Other NSAIDs (including aspirin):** Increased risk of gastrointestinal and renal adverse effects. Avoid concurrent use.
* **ACE inhibitors and ARBs:** May reduce antihypertensive effect and increase risk of renal dysfunction.
* **Diuretics:** May reduce diuretic efficacy and increase risk of renal dysfunction.
* **Lithium:** Increased lithium levels and risk of toxicity. Monitor lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Gastrointestinal:** Monitor for signs and symptoms of bleeding (melena, hematemesis, abdominal pain).
* **Renal:** Monitor renal function (BUN, creatinine) especially in patients with pre-existing renal disease or those taking concomitant nephrotoxic agents.
* **Hepatic:** Monitor liver function tests (AST, ALT) especially in patients with pre-existing hepatic disease.
* **Cardiovascular:** Assess for signs of cardiovascular events.
## Clinical Pearls
* Mefenamic acid is generally recommended for short-term use only (up to 7 days).
* It is most effective when taken with food or milk to minimize gastrointestinal upset.
* Due to potential adverse effects, especially gastrointestinal bleeding and cardiovascular events, it should be used at the lowest effective dose for the shortest duration necessary.
* Consider NSAID-associated risks, particularly in elderly patients or those with a history of GI disease or cardiovascular risk factors.
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**Disclaimer:** This information is for educational purposes only and does not substitute for professional medical advice. Always consult with a qualified healthcare provider to ensure the information provided is appropriate for your specific situation and to review the most current prescribing information.
