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# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID) that exhibits analgesic, anti-inflammatory, and antipyretic properties. It acts primarily by inhibiting the cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Treatment of mild to moderate pain.
* Primary dysmenorrhea (common off-label or indicated use depending on geographic availability).
## Adult Dosing
* **Dysmenorrhea/Pain:** 500 mg orally as an initial dose, followed by 250 mg every 6 hours as needed.
* **Maximum Duration:** Therapy should not exceed 7 days for pain.
## Pediatric Dosing
* **Safety/Efficacy:** Not established for children under 14 years of age. Use in this population is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Avoid in patients with severe renal impairment (CrCl <30 mL/min). Use with caution in mild-to-moderate impairment.
* **Hepatic Impairment:** Use with caution; monitor for hepatotoxicity. Dose reduction may be necessary if liver function is compromised.
## Contraindications
* Known hypersensitivity to mefenamic acid or aspirin/other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Peri-operative pain management in the setting of coronary artery bypass graft (CABG) surgery.
* Active peptic ulcer disease or history of gastrointestinal (GI) bleeding.
* Severe renal, hepatic, or cardiac failure.
* Third trimester of pregnancy (risk of premature closure of the ductus arteriosus).
## Adverse Effects
* **Common:** GI disturbances (nausea, abdominal pain, diarrhea, dyspepsia), dizziness, headache.
* **Serious:** GI ulceration/perforation, gastrointestinal bleeding, cardiovascular events (myocardial infarction, stroke), hypertension, renal failure, fluid retention/edema, severe skin reactions (SJS/TEN).
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding.
* **Antiplatelet agents/SSRIs:** Increased risk of GI bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium/Methotrexate:** Potential for increased serum concentrations and toxicity due to reduced renal clearance.
## Monitoring
* **Renal/Hepatic:** Periodic monitoring of serum creatinine, BUN, and liver function tests during long-term therapy.
* **GI:** Monitor for signs of occult blood loss or symptoms of peptic ulcer disease.
* **Blood Pressure:** Monitor periodically, as NSAIDs can induce hypertension.
## Clinical Pearls
* Take with food or milk to minimize gastric irritation.
* Consistent with other NSAIDs, it carries a Boxed Warning regarding an increased risk of serious cardiovascular thrombotic events and serious gastrointestinal adverse events.
* Discontinue use if symptoms of liver dysfunction or skin rash occur.
* Mefenamic acid is generally not recommended for chronic use; treatment should be as short-term as possible.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice protocols and prescribing information may vary by region and institutional policy. Always verify specific dosing, safety profiles, and current package inserts through reliable, updated pharmacological databases (e.g., Lexicomp, UpToDate) or consultation with a specialist before prescribing or administering medication.
