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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 management of mild to moderate pain.
* Primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg.
* **Primary Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain or bleeding, whichever comes first.
## Pediatric Dosing
Mefenamic acid is generally **not recommended** for pediatric patients under 14 years of age due to lack of established safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Significant renal impairment may require dose reduction or discontinuation. Data on specific dose adjustments is limited.
* **Hepatic Impairment:** Use with caution. Data on specific dose adjustments is limited.
## Contraindications
* Known hypersensitivity to mefenamic acid 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.
* Active gastrointestinal (GI) bleeding or a history of recurrent GI ulceration/bleeding.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
Common: Nausea, vomiting, diarrhea, abdominal pain, constipation, dizziness, headache, rash, fluid retention, edema.
Serious:
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and heart failure.
* **Gastrointestinal:** Ulceration, bleeding, perforation of stomach, small intestine, or large intestine.
* **Renal:** Acute kidney injury, interstitial nephritis, papillary necrosis.
* **Hepatic:** Liver enzyme elevations, hepatitis.
* **Hematologic:** Anemia, thrombocytopenia, leukopenia.
* **Hypersensitivity:** Anaphylaxis, angioedema, 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.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Other NSAIDs and Aspirin:** Increased risk of GI toxicity and potential for additive pharmacodynamic effects.
* **Diuretics and Antihypertensives:** May reduce their efficacy and increase risk of renal toxicity.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Monitor for signs of cardiovascular events (e.g., chest pain, shortness of breath).
* Monitor renal function (BUN, creatinine) and liver function tests (ALT, AST), especially with long-term use or in patients with pre-existing renal or hepatic disease.
* Monitor for signs of hypersensitivity reactions.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* It should be taken with food or milk to minimize GI upset.
* The lowest effective dose should be used for the shortest duration necessary.
* Due to its potential for GI toxicity, consider co-administration with a proton pump inhibitor (PPI) in patients at high risk for GI events.
* Avoid concomitant use with other NSAIDs.
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**Disclaimer:** This information is intended for clinical decision support and is not a substitute for professional medical advice. Always consult the most current prescribing information and clinical guidelines for definitive drug management decisions.
