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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term management of mild to moderate pain. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Pain, including menstrual pain (dysmenorrhea) and pain associated with musculoskeletal disorders.
## Adult Dosing
* **Initial dose:** 500 mg.
* **Subsequent doses:** 250 mg every 6 hours as needed.
* **Maximum daily dose:** 1500 mg.
* **Duration:** Typically for short-term use only (maximum 7 days for pain).
## Pediatric Dosing
* **Children 14 years and older:** Same as adult dosing.
* **Children younger than 14 years:** Dosing has not been established. Safety and efficacy in this age group are not well-documented.
## Dose Adjustments
* **Renal Impairment:** Use with caution; may require dose reduction or increased monitoring. Data is limited.
* **Hepatic Impairment:** Use with caution; may require dose reduction or increased monitoring. 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.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or history of GI bleeding/ulceration.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, headache, dizziness, rash.
* **Serious:**
* **GI:** Ulceration, bleeding, perforation (especially with prolonged use or in elderly patients).
* **Cardiovascular:** Increased risk of thrombotic events (myocardial infarction, stroke), hypertension.
* **Renal:** Acute kidney injury, interstitial nephritis.
* **Hepatic:** Elevated liver enzymes, hepatitis.
* **Hypersensitivity:** Anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis.
* **Hematologic:** Anemia, thrombocytopenia.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Antiplatelet agents (e.g., aspirin, clopidogrel):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Diuretics and antihypertensives (e.g., ACE inhibitors, ARBs):** May reduce efficacy and increase risk of renal impairment.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased methotrexate levels and toxicity.
* **Other NSAIDs:** Increased risk of adverse effects.
## Monitoring
* Signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Renal function (e.g., serum creatinine, BUN).
* Liver function (e.g., AST, ALT).
* Blood pressure.
* Signs of cardiovascular events.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize GI upset.
* Due to its short half-life, it is typically dosed every 6 hours.
* Limit duration of use to the shortest effective period to minimize risks.
* Consider alternatives for patients with a history of GI issues, cardiovascular disease, or renal impairment.
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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 or a qualified healthcare provider for any questions regarding medications.
