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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. Its mechanism of action involves the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Dysmenorrhea (menstrual pain)
* Mild to moderate pain, including dental pain and pain associated with musculoskeletal conditions.
## Adult Dosing
* **Dysmenorrhea:** 500 mg every 4 to 6 hours as needed.
* **Mild to moderate pain:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum dose:** Not to exceed 1500 mg in 24 hours. Treatment duration typically should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for use in children under 14 years of age due to limited safety and efficacy data. For approved indications in specific populations, consult pediatric-specific guidelines.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data for specific dose adjustments are limited; monitor renal function closely.
* **Hepatic Impairment:** Use with caution. Data for specific dose adjustments are limited; monitor hepatic function closely.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal events. Consider a lower starting dose and increased monitoring.
## Contraindications
* Known 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.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis).
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Gastrointestinal upset (nausea, vomiting, diarrhea, abdominal pain), headache, dizziness.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (myocardial infarction, stroke); renal impairment; hepatic dysfunction; hypersensitivity reactions (including anaphylaxis); Stevens-Johnson syndrome/toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **SSRIs/SNRIs:** Increased risk of gastrointestinal bleeding.
* **Diuretics:** Reduced efficacy and increased risk of nephrotoxicity.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Gastrointestinal:** Monitor for signs and symptoms of bleeding (e.g., melena, hematemesis) and ulceration.
* **Cardiovascular:** Assess cardiovascular risk factors and monitor for signs of thrombotic events.
* **Renal:** Monitor renal function (serum creatinine, BUN) especially in patients with pre-existing renal disease or those at risk.
* **Hepatic:** Monitor liver function tests (ALT, AST) in patients with hepatic impairment or those receiving long-term therapy.
* **Blood Pressure:** NSAIDs can elevate blood pressure; monitor accordingly.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* It is generally recommended for short-term use only.
* Due to its potential for renal and gastrointestinal toxicity, it should be used at the lowest effective dose for the shortest possible duration.
* Consider alternative analgesics if patient has significant cardiovascular, renal, or hepatic disease, or a history of gastrointestinal bleeding.
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*This information is intended for clinical decision-making support and does not replace professional medical judgment. Always consult the most current prescribing information, local guidelines, and individual patient factors before initiating or modifying drug therapy.*
