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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It possesses analgesic and anti-inflammatory properties through non-selective inhibition of cyclooxygenase (COX) enzymes, subsequently reducing prostaglandin synthesis.
## Primary Indications
* Treatment of mild to moderate pain.
* Primary dysmenorrhea.
* *Note: Treatment duration should generally not exceed 7 days.*
## Adult Dosing
* **Initial Dose:** 500 mg orally.
* **Maintenance:** 250 mg orally every 6 hours as needed.
* **Maximum Dose:** 1500 mg per day.
## Pediatric Dosing
* **Age ≥14 years:** Use adult dosing.
* **Age <14 years:** Safety and efficacy are not established. Use is generally avoided unless specialized pediatric protocols dictate otherwise.
## Dose Adjustments
* **Renal Impairment:** Avoid in patients with severe renal impairment (CrCl <30 mL/min). Use with caution in moderate impairment.
* **Hepatic Impairment:** Reduce dose or avoid if possible. Monitor liver function closely.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of asthma or urticaria triggered by aspirin/NSAIDs.
* Active peptic ulcer disease or gastrointestinal bleeding.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Severe renal or hepatic failure.
## Adverse Effects
* **Gastrointestinal:** Nausea, abdominal pain, diarrhea (can be severe), gastrointestinal ulceration/bleeding.
* **Renal:** Fluid retention, edema, acute kidney injury.
* **Cardiovascular:** Hypertension, increased risk of thrombotic events (e.g., MI, stroke).
* **Systemic:** Headache, dizziness, blood dyscrasias.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding.
* **Antiplatelets/SSRIs:** Increased risk of gastrointestinal bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of acute renal failure.
* **Lithium/Methotrexate:** Decreased clearance, leading to potential toxicity.
## Monitoring
* **Periodic:** Renal function (creatinine, BUN), liver function tests, complete blood count (if long-term/chronic use occurs).
* **Clinical:** Blood pressure control, signs of GI bleeding (black, tarry stools), and occult blood.
## Clinical Pearls
* **Diarrhea:** Mefenamic acid is more frequently associated with diarrhea than other NSAIDs; discontinue if diarrhea is persistent.
* **Dosing Duration:** Due to the risk of significant GI toxicity and hematologic side effects, therapy should be limited to the shortest duration possible.
* **Food:** Administer with food or milk to decrease gastrointestinal irritation.
* **CV Risk:** Use the lowest effective dose for the shortest duration possible, especially in patients with existing cardiovascular disease.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice guidelines vary by region and institution. Always verify specific dosing, safety profiles, and indications via your facility’s clinical decision support system or official package inserts before prescribing or administering medication.
