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# Mefenamic acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Short-term relief of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 4-6 hours as needed. Do not exceed 1500 mg in any 24-hour period for the first 7 days of treatment. For longer-term use, do not exceed 1000 mg every 4-6 hours.
* **Dysmenorrhea:** 500 mg every 4-6 hours as needed, starting at the onset of menstrual pain, bloating, and/or abdominal cramps.
## Pediatric Dosing
* Mefenamic acid is **not recommended** for use in pediatric patients under 14 years of age. Safety and efficacy have not been established.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe renal impairment, but specific guidelines are lacking.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe hepatic impairment, but specific guidelines are lacking.
## Contraindications
* 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.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, rash, dizziness, headache.
* **Serious:** Cardiovascular thrombotic events, myocardial infarction, stroke, gastrointestinal bleeding, ulceration, perforation, renal failure, hepatic failure, anaphylactic reactions, Stevens-Johnson syndrome, toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Aspirin:** May decrease the cardioprotective effects of low-dose aspirin.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding and ulceration.
* **Diuretics and Antihypertensives:** May reduce their efficacy and increase the risk of renal impairment.
* **Lithium:** Increased lithium levels and toxicity. Monitor lithium levels.
* **Methotrexate:** Increased methotrexate levels and toxicity. Monitor for signs of methotrexate toxicity.
## Monitoring
* **Renal Function:** Periodically monitor BUN and serum creatinine, especially in patients with pre-existing renal disease or those on prolonged therapy.
* **Hepatic Function:** Periodically monitor liver enzymes, especially in patients with pre-existing liver disease.
* **Gastrointestinal Symptoms:** Advise patients to report any signs of bleeding or ulceration (e.g., black, tarry stools, persistent abdominal pain, vomiting blood).
* **Blood Pressure:** Monitor blood pressure, particularly during initiation and with prolonged use.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* It should be taken with food or milk to minimize gastrointestinal upset.
* Hydration is important to prevent potential renal toxicity.
* Avoid concomitant use with other NSAIDs.
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**Disclaimer:** This information is intended for clinical use and does not replace the manufacturer's prescribing information or clinical judgment. Always verify current prescribing information with the latest official product labeling and relevant guidelines before making any treatment decisions.
