Please check your internet connection and try again.
# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID) that exhibits analgesic, anti-inflammatory, and antipyretic properties. Like other NSAIDs, it inhibits cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Treatment of mild to moderate pain.
* Primary dysmenorrhea.
* Off-label: Menorrhagia.
## Adult Dosing
* **Pain/Dysmenorrhea:** 500 mg orally initially, followed by 250 mg every 6 hours as needed.
* **Maximum Duration:** Therapy should not exceed 7 days.
* **Maximum Dose:** 1500 mg per day.
## Pediatric Dosing
* **Adolescents (≥14 years):** Same as adult dosing (500 mg load, then 250 mg every 6 hours).
* **Children (<14 years):** Safety and efficacy are not established. Use is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Avoid in patients with severe renal impairment (CrCl <30 mL/min). Use caution and monitor closely in mild-to-moderate impairment.
* **Hepatic Impairment:** Use with caution; monitor for hepatotoxicity. Dose reduction may be required.
* **Geriatric:** Use the lowest effective dose for the shortest duration due to increased risk of gastrointestinal bleeding and renal/cardiovascular adverse effects.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs (risk of anaphylaxis/angioedema).
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Use in the setting of coronary artery bypass graft (CABG) surgery.
* Active peptic ulcer disease or history of GI bleeding.
* Severe renal or hepatic impairment.
## Adverse Effects
* **Common:** Abdominal pain, nausea, diarrhea (often transient and dose-dependent), dizziness, headache.
* **Serious:** Cardiovascular thrombotic events (myocardial infarction, stroke), GI bleeding/ulceration, nephrotoxicity, hepatotoxicity, fluid retention, edema, and skin reactions (e.g., Stevens-Johnson syndrome).
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding; monitor INR frequently.
* **Antiplatelets/SSRIs:** Increased risk of GI bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** May diminish antihypertensive effect and increase risk of acute renal failure.
* **Lithium/Methotrexate:** NSAIDs may decrease clearance, leading to increased serum levels and potential toxicity.
## Monitoring
* **Renal Function:** Serum creatinine and electrolytes (potassium) periodically in high-risk patients.
* **GI:** Monitor for signs/symptoms of gastrointestinal bleeding (melena, hematemesis, unexplained anemia).
* **Blood Pressure:** Monitor periodically, as NSAIDs can cause or exacerbate hypertension.
* **Hepatic:** Liver function tests if symptoms of liver dysfunction appear.
## Clinical Pearls
* **GI Sensitivity:** Gastrointestinal toxicity is relatively common with mefenamic acid; diarrhea is a signature side effect that occurs more frequently than with other NSAIDs.
* **Food:** Administration with food or milk may reduce GI irritation.
* **Short-Term Use:** Due to the risk of hemolytic anemia and diarrhea, this agent is specifically labeled for short-term use (maximum 7 days). It is not intended for chronic inflammatory conditions like rheumatoid arthritis.
* **Prostaglandin Inhibition:** Like other NSAIDs, it may impair female fertility; reversible upon discontinuation.
***
**Educational Disclaimer:** This information is for educational purposes only. Clinical guidelines and prescribing information change frequently. Always consult the most current official product labeling (FDA or local regulatory authority) and institutional protocols before prescribing or administering any medication.
