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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It functions by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed. Maximum daily dose is 1500 mg.
* **Dysmenorrhea:** 500 mg every 4 to 6 hours as needed, starting with the onset of pain and bleeding. Maximum daily dose is 1500 mg.
## Pediatric Dosing
Dosing for children under 14 years of age is not well-established and is generally not recommended.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, however caution is advised. NSAIDs should be used at the lowest effective dose for the shortest duration necessary.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, 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 or bleeding.
* Severe heart failure.
* Severe renal impairment.
* Severe hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, and rash. Serious adverse effects include gastrointestinal bleeding and perforation, cardiovascular thrombotic events, renal toxicity, hepatic toxicity, hypersensitivity reactions, and exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of GI bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of adverse effects, particularly GI bleeding.
* **Diuretics and antihypertensives:** May reduce their efficacy and increase the risk of renal impairment.
* **Lithium:** May increase serum lithium levels.
* **Methotrexate:** May increase methotrexate toxicity.
## Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Monitor for signs and symptoms of cardiovascular events (e.g., chest pain, shortness of breath).
* Monitor renal function (BUN, creatinine) and liver function tests (ALT, AST), especially with prolonged use or in patients with pre-existing renal or hepatic disease.
* Monitor blood pressure.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize GI upset.
* Due to the risk of serious GI events, mefenamic acid should be used at the lowest effective dose for the shortest duration necessary.
* Patients with pre-existing GI disease should be closely monitored.
* Consider the risks versus benefits, especially in elderly patients or those with cardiovascular disease.
* It is generally recommended for short-term use only.
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**Disclaimer:** This information is intended for clinical use and does not replace professional medical advice. Always consult the most current prescribing information and product monographs for complete details and to verify information before making clinical decisions.
