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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class.
## Primary Indications
* Mild to moderate pain, including dysmenorrhea.
* Rheumatoid arthritis and osteoarthritis (though less commonly used due to GI risks).
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting with the onset of pain and continuing for up to 3 days.
* **Maximum daily dose:** 1500 mg. Doses exceeding 1500 mg/day are generally not recommended due to increased risk of adverse effects.
## Pediatric Dosing
* **Age 14 years and older:** Same as adult dosing.
* **Younger than 14 years:** Dosing is not well established and generally not recommended due to potential safety concerns.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustment is universally recommended, but reduced frequency or dose may be considered. Monitor renal function closely.
* **Hepatic Impairment:** Use with caution. No specific dose adjustment is universally recommended. Monitor liver function.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of NSAID-induced bronchospasm, asthma, urticaria, or allergic-type reactions.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, dizziness, headache.
* **Serious:** Gastrointestinal bleeding, ulceration, and perforation; renal toxicity; hepatic toxicity; cardiovascular thrombotic events; hypersensitivity reactions; exacerbation of asthma; 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.
* **ACE inhibitors, ARBs, diuretics:** May reduce antihypertensive effect and increase risk of renal impairment.
* **Lithium:** Increased lithium levels.
* **Methotrexate:** Increased methotrexate levels and potential for methotrexate toxicity.
* **Other NSAIDs/Aspirin:** Increased risk of adverse effects.
## Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease, dehydration, or those on concurrent nephrotoxic agents.
* **Hepatic function:** Especially in patients with liver disease.
* **Signs and symptoms of GI bleeding:** Hemoccult stool, melena, hematemesis.
* **Blood pressure:** NSAIDs can increase blood pressure.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* It is typically used for short-term pain management due to its gastrointestinal safety profile compared to other NSAIDs.
* Long-term use is not recommended.
* The total duration of therapy should not exceed 7 days for pain or 3 days for dysmenorrhea.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before prescribing or administering any medication. Dosing and indications may vary based on local protocols and individual patient factors.
