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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative class. It possesses analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea).
* Relief of signs and symptoms of rheumatoid arthritis and osteoarthritis (less commonly used due to potential GI toxicity).
## Adult Dosing
* **Pain/Dysmenorrhea:** 500 mg every 6 hours as needed. Treatment should not exceed 7 days.
* **Rheumatoid Arthritis/Osteoarthritis:** 500 mg three times daily.
**Maximum Dose:** 1500 mg per day for all indications.
## Pediatric Dosing
Mefenamic acid is **not recommended** for use in children under 14 years of age due to potential for serious adverse effects, particularly renal.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustment is established, but monitor renal function closely.
* **Hepatic Impairment:** Use with caution. No specific dose adjustment is established, but monitor hepatic function closely.
## Contraindications
* 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.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include diarrhea, nausea, vomiting, abdominal pain, constipation, and dizziness.
Serious adverse effects include:
* Gastrointestinal: Bleeding, ulceration, perforation.
* Cardiovascular: Myocardial infarction, stroke, hypertension.
* Renal: Acute kidney injury, interstitial nephritis.
* Hepatic: Hepatotoxicity, elevated liver enzymes.
* Dermatologic: Severe skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis).
* Hematologic: Anemia, leukopenia, thrombocytopenia.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding.
* **SSRIs and SNRIs:** Increased risk of bleeding.
* **Diuretics and Antihypertensives:** NSAIDs may reduce their efficacy and increase the risk of renal toxicity.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease, dehydration, or those taking concomitant nephrotoxic agents.
* **Hepatic function:** Particularly with long-term use.
* **Gastrointestinal symptoms:** Monitor for signs of bleeding or ulceration.
* **Blood pressure:** NSAIDs can increase blood pressure.
## Clinical Pearls
* Due to its short half-life, mefenamic acid requires frequent dosing, which can impact adherence.
* Diarrhea is a common dose-limiting side effect.
* It is generally recommended to use the lowest effective dose for the shortest duration necessary to minimize risks.
* Mefenamic acid should be taken with food or milk to reduce gastrointestinal upset.
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*This information is for educational purposes and does not substitute for professional medical advice. Always verify current prescribing information with the latest official drug monographs or product inserts.*
