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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It exhibits analgesic, anti-inflammatory, and antipyretic properties through the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Dysmenorrhea (menstrual pain)
* Mild to moderate pain (e.g., dental pain, musculoskeletal pain)
## Adult Dosing
* **Dysmenorrhea:** 500 mg every 4 to 6 hours as needed. Do not exceed 1500 mg in 24 hours.
* **Mild to moderate pain:** 500 mg every 4 to 6 hours as needed. Do not exceed 1500 mg in 24 hours.
* **Duration of therapy:** Generally limited to 7 days.
## Pediatric Dosing
Mefenamic acid is **not recommended** for use in children under 14 years of age due to limited data and potential for adverse effects.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but dose reduction may be necessary in severe impairment. Monitor renal function.
* **Hepatic Impairment:** Use with caution. Data is limited, but dose reduction may be necessary in severe impairment. Monitor liver function.
## 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.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal bleeding or history of gastrointestinal bleeding or perforation related to prior NSAID use.
* Severe renal impairment (CrCl < 30 mL/min).
* Severe hepatic impairment.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, dizziness, headache, rash.
* **Serious:**
* Cardiovascular thrombotic events (myocardial infarction, stroke)
* Gastrointestinal bleeding, ulceration, and perforation
* Hepatotoxicity (elevated liver enzymes, hepatitis, jaundice)
* Nephrotoxicity (acute kidney injury, interstitial nephritis, papillary necrosis)
* Serious skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis)
* Anaphylactic reactions
* Exacerbation of asthma
## Key Drug Interactions
* **ACE Inhibitors/ARBs:** Increased risk of renal impairment.
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Aspirin:** May decrease the cardioprotective effects of low-dose aspirin. Increased risk of GI toxicity.
* **Corticosteroids:** Increased risk of GI bleeding.
* **Diuretics:** May decrease diuretic efficacy and increase risk of nephrotoxicity.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate levels and risk of toxicity.
* **SSRIs:** Increased risk of GI bleeding.
## Monitoring
* **Baseline and periodic assessment of renal and hepatic function.**
* **Monitor for signs and symptoms of GI bleeding or ulceration.**
* **Monitor blood pressure.**
* **Assess for signs of hypersensitivity or skin reactions.**
## Clinical Pearls
* Mefenamic acid has a relatively short duration of action, requiring frequent dosing.
* It should be taken with food or milk to minimize gastrointestinal upset.
* Avoid concurrent use with other NSAIDs.
* Due to the risk of serious adverse effects, use the lowest effective dose for the shortest possible duration.
* Contraindicated in the third trimester of pregnancy.
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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 and relevant guidelines for definitive guidance.
