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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
* **Pain:** Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea), dental pain, and post-operative pain.
* **Inflammation:** Management of inflammatory conditions.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum dose is 1500 mg in a 24-hour period.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
## Pediatric Dosing
Mefenamic acid is generally 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. Dose reduction may be necessary in severe renal impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe hepatic impairment.
## 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 (GI) bleeding or ulceration.
* Severe heart failure.
* Late pregnancy (third trimester).
## Adverse Effects
**Common:**
* GI: Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia.
* CNS: Dizziness, headache, drowsiness.
**Serious:**
* GI: GI bleeding, ulceration, perforation.
* Cardiovascular: Increased risk of myocardial infarction, stroke, and related events. Hypertension.
* Renal: Renal papillary necrosis, interstitial nephritis, renal failure.
* Hepatic: Hepatotoxicity, jaundice.
* Hematologic: Anemia, leukopenia, thrombocytopenia.
* Dermatologic: Stevens-Johnson syndrome, toxic epidermal necrolysis.
* Hypersensitivity: Anaphylaxis, angioedema.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Aspirin:** Decreased antiplatelet effect of aspirin; increased GI risk.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Diuretics:** Reduced diuretic effect; increased risk of renal toxicity.
* **Lithium:** Increased serum lithium levels, potentially to toxic levels.
* **Methotrexate:** Increased methotrexate levels and toxicity.
* **Other NSAIDs:** Increased risk of GI, renal, and cardiovascular adverse effects.
## Monitoring
* **GI symptoms:** Monitor for signs and symptoms of GI bleeding or ulceration.
* **Renal function:** Monitor serum creatinine and BUN, especially in patients with pre-existing renal disease.
* **Hepatic function:** Monitor liver enzymes.
* **Blood pressure:** Monitor for new-onset or worsening hypertension.
* **Cardiovascular risk factors:** Assess and manage appropriately.
## Clinical Pearls
* Administer with food or milk to minimize GI upset.
* Limit duration of use to the shortest effective period due to potential for serious GI and cardiovascular events.
* Not a substitute for opioid analgesics in severe pain.
* Avoid concurrent use with other NSAIDs, including aspirin unless specifically indicated for cardioprotection at a low dose.
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**Disclaimer:** This information is intended for educational purposes only and does not substitute for professional medical advice. Always consult with a qualified healthcare provider and refer to the most current prescribing information for definitive guidance.
