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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative class. It exerts its effects by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Mild to moderate pain, including menstrual pain (dysmenorrhea).
* Inflammation associated with various conditions.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum Daily Dose:** 1500 mg. Treatment duration should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for use in children under 14 years of age due to limited safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe impairment. Data is limited.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe impairment. Data 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.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal bleeding or ulceration.
* Severe renal or hepatic impairment.
* Pregnancy in the third trimester.
## Adverse Effects
Common adverse effects include:
* Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation.
* Central Nervous System: Dizziness, drowsiness, headache.
* Renal: Fluid retention, edema.
* Hematologic: Anemia.
* Dermatologic: Rash.
Serious adverse effects include:
* Gastrointestinal: Ulceration, bleeding, perforation.
* Cardiovascular: Increased risk of myocardial infarction and stroke.
* Renal: Acute kidney injury.
* Hepatic: Liver enzyme elevations, jaundice.
* Hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Diuretics:** Reduced diuretic effect; increased risk of nephrotoxicity.
* **Lithium:** Increased lithium levels and potential for toxicity.
* **Methotrexate:** Increased methotrexate levels and potential for toxicity.
* **Other NSAIDs/Aspirin:** Increased risk of adverse effects, especially gastrointestinal 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, especially in patients with pre-existing hepatic disease or those at risk.
* **Blood pressure:** NSAIDs can increase blood pressure.
* **Signs and symptoms of gastrointestinal bleeding:** Monitor for occult blood in stool, melena, hematemesis.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Due to its potential for serious adverse effects, it should be used at the lowest effective dose for the shortest possible duration.
* Avoid concomitant use with other NSAIDs.
* Consider gastroprotection (e.g., proton pump inhibitor) in patients with increased risk of gastrointestinal bleeding.
* Its use in children is limited.
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*Disclaimer: This information is intended for healthcare professionals and does not replace a thorough review of the current prescribing information, institutional protocols, or clinical judgment. Always verify the most up-to-date drug information before making clinical decisions.*
