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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 by inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Treatment of mild to moderate pain.
* Treatment of primary dysmenorrhea.
* *Note:* Use is generally limited to short-term therapy (not exceeding 7 days).
## Adult Dosing
* **Initial Dose:** 500 mg orally.
* **Maintenance Dose:** 250 mg orally every 6 hours as needed.
* **Maximum Daily Dose:** 1,500 mg/day.
## Pediatric Dosing
* **Adolescents (≥14 years):** Follow adult dosing schedule.
* **Children (<14 years):** Safety and efficacy have not been established. Clinical use in this population is generally avoided.
## Dose Adjustments
* **Renal Impairment:** Avoid use in patients with severe renal impairment (CrCl <30 mL/min). Use with caution in mild-to-moderate impairment; monitor renal function closely.
* **Hepatic Impairment:** Avoid use in patients with active hepatic disease; use with caution in individuals with histories of liver impairment.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs/aspirin (risk of bronchospasm or anaphylaxis).
* 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.
* History of gastrointestinal (GI) bleeding or active ulceration.
* Severe renal or hepatic failure.
## Adverse Effects
* **GI:** Diarrhea (common, may be severe), nausea, abdominal pain, dyspepsia, risk of GI ulceration/perforation.
* **Renal/CV:** Fluid retention, edema, increased blood pressure, acute kidney injury.
* **Hematologic:** Increased risk of bleeding (antiplatelet effect).
* **Neurologic:** Dizziness, drowsiness, nervousness.
* **Serious:** Potential for serious cardiovascular thrombotic events and increased risk of serious GI adverse events.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increases risk of bleeding.
* **Antiplatelet Agents/SSRIs:** Increased risk of GI bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of acute kidney injury.
* **Lithium/Methotrexate:** May increase serum concentrations and toxicity risk.
## Monitoring
* **Renal Function:** Periodic BUN/creatinine, especially in elderly or chronic users.
* **Blood Pressure:** Monitor regularly during initiation and dose increases.
* **Hematologic:** Monitor for signs of occult blood loss (e.g., CBC if therapy is prolonged).
* **GI Symptoms:** Monitor for signs of bleeding, perforation, or ulceration.
## Clinical Pearls
* **GI Toxicity:** Mefenamic acid is known for a higher incidence of GI-related side effects, particularly diarrhea, compared to other NSAIDs.
* **Duration:** Limit total duration of treatment to 7 days due to cumulative risk of toxicity.
* **Administration:** Administer with food or milk to decrease the incidence of GI upset.
* **CV Risk:** All non-aspirin NSAIDs share an increased risk of serious cardiovascular thrombotic events (myocardial infarction and stroke).
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**Educational Disclaimer:** This information is for educational purposes only. Always verify drug dosages, contraindications, and interaction profiles via the current product labeling (e.g., FDA package insert) or institutional clinical decision support tools before prescribing or administering medication.
