Please check your internet connection and try again.
# Mefenamic Acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID). It exerts anti-inflammatory, analgesic, and antipyretic effects primarily through the non-selective inhibition of cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Treatment of primary dysmenorrhea.
* Short-term management of mild to moderate pain (up to 7 days).
## Adult Dosing
* **Dysmenorrhea/Pain:** 500 mg orally as an initial dose, followed by 250 mg orally every 6 hours as needed.
* **Maximum Dose:** Do not exceed 1,000 mg per day or therapy duration exceeding 7 days.
## Pediatric Dosing
* **Children ≥14 years:** Use adult dosing (500 mg initial, then 250 mg every 6 hours).
* **Children <14 years:** Safety and efficacy have not been established. Use for this population is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Avoid in patients with severe renal impairment (CrCl <30 mL/min). Use with caution and monitor carefully in mild-to-moderate impairment.
* **Hepatic Impairment:** Use with caution. Monitor liver function closely; discontinue if abnormal tests persist or worsen.
## 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.
* History of gastrointestinal (GI) bleeding or perforation related to previous NSAID therapy.
* Active peptic ulcer disease or inflammatory bowel disease.
* Pre-operative pain setting for coronary artery bypass graft (CABG) surgery.
* Severe renal or hepatic impairment.
## Adverse Effects
* **GI:** Diarrhea (most common), nausea, abdominal pain, GI ulceration, bleeding, and perforation.
* **Renal:** Fluid retention, edema, acute renal failure, interstitial nephritis.
* **Cardiovascular:** Hypertension, increased risk of myocardial infarction and stroke (class effect of non-aspirin NSAIDs).
* **Hematologic:** Anemia, blood dyscrasias.
* **Dermatologic:** Rash, pruritus, severe skin reactions (Stevens-Johnson syndrome).
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding due to antiplatelet effects and gastric mucosal injury.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect; increased risk of acute kidney injury.
* **Lithium:** May increase serum lithium concentrations to toxic levels.
* **Methotrexate:** May increase methotrexate toxicity by reducing renal clearance.
## Monitoring
* **Baseline:** CBC, serum creatinine, and liver function tests (LFTs) for prolonged therapy.
* **Ongoing:** Monitor for signs of GI bleeding (occult blood, anemia), fluid retention (weight, blood pressure), and changes in renal function.
## Clinical Pearls
* **Duration Limit:** Mefenamic acid is strictly indicated for short-term use (≤ 7 days). Long-term use significantly increases the risk of serious GI and cardiovascular toxicity.
* **Administration:** Take with food or milk to minimize GI irritation.
* **Diarrhea:** Diarrhea is uniquely associated with mefenamic acid compared to other NSAIDs; it may be dose-related and necessitate discontinuation if it occurs.
* **NSAID Stewardship:** Avoid concurrent use of multiple NSAIDs due to cumulative toxicity.
***
**Disclaimer:** This information is for educational purposes and does not substitute professional clinical judgment. Always consult the most current prescribing information (e.g., FDA label or local formulary) and patient-specific medical history before prescribing or administering medication.
