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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative 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 orally every 4-6 hours as needed. Maximum daily dose is 1500 mg. Treatment should not exceed 7 days.
* **Dysmenorrhea:** 500 mg orally every 4-6 hours as needed, typically starting with the onset of pain and continuing for the duration of symptoms. Maximum daily dose is 1500 mg. Treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is **not recommended** for use in children under 14 years of age due to lack of established safety and efficacy.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, but caution is advised. Mefenamic acid should be used with caution in patients with pre-existing renal or hepatic disease, and the lowest effective dose should be employed.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* 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.
* Inflammatory bowel disease.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, headache, dizziness, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, and perforation; renal impairment; hepatic toxicity; cardiovascular thrombotic events (MI, stroke); hypersensitivity reactions; exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of gastrointestinal adverse effects and potential for additive pharmacodynamic effects.
* **ACE inhibitors, ARBs, diuretics:** Reduced antihypertensive efficacy and increased risk of renal impairment.
* **Lithium, Methotrexate:** Increased serum concentrations and toxicity. Monitor lithium and methotrexate levels.
## Monitoring
* Monitor for signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis).
* Assess renal function (serum creatinine, BUN) periodically, especially in patients with risk factors for renal impairment.
* Monitor liver function tests periodically, especially with long-term use or in patients with pre-existing liver disease.
* Assess for signs of cardiovascular events.
## Clinical Pearls
* Administer with food or milk to minimize gastrointestinal upset.
* Limit duration of use to the shortest effective period, generally no more than 7 days, due to risks of serious adverse events.
* Avoid concomitant use with other NSAIDs.
* Not a first-line agent for chronic pain due to safety concerns.
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*Disclaimer: This information is intended for healthcare professionals and does not replace the need to consult the most current prescribing information or specific clinical guidelines.*
