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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) from the fenamate class. It is a weak acid and an inhibitor of prostaglandin synthesis.
## Primary Indications
* Short-term relief of mild to moderate pain, including menstrual pain (dysmenorrhea) and pain associated with inflammation.
## Adult Dosing
* **Pain/Dysmenorrhea:** 500 mg every 4 to 6 hours as needed.
* **Maximum Daily Dose:** 1500 mg (typically limited to 7 days of use).
## Pediatric Dosing
* **Age ≥ 14 years:** Dosing is the same as adults.
* **Age < 14 years:** Mefenamic acid is generally not recommended due to limited safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe impairment, though specific guidelines are lacking.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe impairment, though specific guidelines are lacking.
* **Elderly:** Increased risk of adverse effects. Use the lowest effective dose.
## 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.
* Severe renal or hepatic impairment.
* History of NSAID-induced gastrointestinal ulceration or bleeding.
## Adverse Effects
* **Common:** Gastrointestinal upset (nausea, vomiting, diarrhea, abdominal pain), headache, dizziness, drowsiness.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal toxicity (including interstitial nephritis, papillary necrosis); hepatic toxicity; cardiovascular thrombotic events; hypersensitivity reactions; Stevens-Johnson syndrome/toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Diuretics and Antihypertensives (e.g., ACE inhibitors, ARBs, beta-blockers):** May reduce their efficacy and increase risk of renal impairment.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Other NSAIDs/Aspirin:** Increased risk of adverse effects, particularly GI bleeding.
## Monitoring
* **Renal function:** Baseline and periodic monitoring, especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** Baseline and periodic monitoring.
* **Gastrointestinal symptoms:** Educate patients on signs of GI bleeding (e.g., black tarry stools, hematemesis) and advise to discontinue and seek medical attention if they occur.
* **Blood pressure:** NSAIDs can increase blood pressure.
## Clinical Pearls
* For short-term use only due to increased risk of serious adverse effects with prolonged use.
* Administer with food or milk to minimize gastrointestinal upset.
* Avoid concurrent use with other NSAIDs.
* Consider gastroprotection (e.g., proton pump inhibitor) in patients with increased risk of GI complications.
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**Disclaimer:** This information is intended for clinical decision support and does not replace professional medical advice. Always consult the most current prescribing information and relevant guidelines before making any treatment decisions.
