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# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID). It exerts analgesic, anti-inflammatory, and antipyretic effects primarily through the inhibition of COX-1 and COX-2 enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Treatment of primary dysmenorrhea.
* Short-term management of mild to moderate pain (usually up to 7 days).
## Adult Dosing
* **Initial Dose:** 500 mg orally.
* **Maintenance Dose:** 250 mg orally every 6 hours as needed.
* **Maximum Duration:** 7 days.
* **Maximum Daily Dose:** Do not exceed 1000 mg/day.
## Pediatric Dosing
* **Children ≥14 years:** Dosing is the same as adults.
* **Children <14 years:** Efficacy and safety have not been established. Use is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Avoid use in severe renal impairment (CrCl <30 mL/min). Use with caution in mild-to-moderate impairment; monitor renal function closely.
* **Hepatic Impairment:** Use with caution; monitor for elevated liver enzymes. Avoid in severe hepatic impairment.
* **Geriatric Patients:** Use the lowest effective dose for the shortest duration due to increased risk of cardiovascular and gastrointestinal toxicities.
## Contraindications
* Hypersensitivity to mefenamic acid or any component of the formulation.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Treatment of peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* History of active gastrointestinal (GI) bleeding or ulceration.
## Adverse Effects
* **Common:** Abdominal pain, dyspepsia, nausea, diarrhea (often dose-limiting), and headache.
* **Serious:** GI bleeding/ulceration, cardiovascular thrombotic events (myocardial infarction, stroke), hypertension, renal failure, fluid retention/edema, and hepatotoxicity.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increases risk of bleeding.
* **Antiplatelet agents/SSRIs:** Increased risk of GI bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** May diminish antihypertensive effects and increase risk of renal impairment (nephrotoxicity).
* **Lithium/Methotrexate:** May increase serum concentrations and toxicity of these drugs due to reduced renal clearance.
## Monitoring
* Baseline and periodic monitoring of serum creatinine, BUN, and electrolytes.
* Monitor hemoglobin/hematocrit if long-term treatment is utilized (due to potential for occult GI blood loss).
* Monitor blood pressure during treatment.
* Observation for signs/symptoms of GI ulceration or cardiovascular events.
## Clinical Pearls
* **GI Irritation:** Take with food or milk to minimize gastrointestinal distress.
* **Diarrhea:** Mefenamic acid is frequently associated with diarrhea; if severe diarrhea occurs, the drug should be discontinued.
* **Cardiovascular Risk:** Like all non-aspirin NSAIDs, mefenamic acid carries a boxed warning for an increased risk of serious cardiovascular thrombotic events.
* **Limited Use:** Its clinical utility is restricted due to a higher frequency of adverse effects (specifically GI) compared to other NSAIDs.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice protocols and prescribing information may vary by region or institution. Always consult the latest official product monograph and local clinical guidelines before prescribing or administering medication.
