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 analgesic, anti-inflammatory, and antipyretic effects primarily through non-selective inhibition of cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Treatment of mild to moderate pain.
* Primary dysmenorrhea.
* *Off-label:* Management of heavy menstrual bleeding (menorrhagia).
## Adult Dosing
* **Pain/Dysmenorrhea:** 500 mg orally as an initial dose, followed by 250 mg every 6 hours as needed.
* **Duration:** Therapy should not exceed 7 days to minimize the risk of gastrointestinal (GI) and renal toxicity.
## Pediatric Dosing
* **Children ≥14 years:** Use adult dosing guidelines (see above).
* **Children <14 years:** Safety and efficacy have not been established; use is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Avoid in patients with advanced renal disease. Use with caution in mild-to-moderate impairment; close monitoring of creatinine clearance is required.
* **Hepatic Impairment:** Use with caution; monitor for signs of hepatic toxicity.
* **Elderly:** Use the lowest effective dose for the shortest duration possible due to increased risk of GI bleeding and renal complications.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs (including aspirin-induced asthma/urticaria).
* History of GI bleeding or perforation related to previous NSAID therapy.
* Active peptic ulcer disease or inflammatory bowel disease.
* Severe renal or hepatic impairment.
* Treatment of perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, abdominal pain, diarrhea (may be severe), dyspepsia, constipation, dizziness, and headache.
* **Serious:** GI ulceration/perforation, myocardial infarction, stroke, heart failure, hypertension, fluid retention, renal impairment, and severe hypersensitivity reactions (e.g., Stevens-Johnson syndrome).
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of major bleeding.
* **Antiplatelet agents, SSRIs, SNRIs:** Increased risk of GI bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of acute kidney injury.
* **Lithium/Methotrexate:** Decreased renal clearance, leading to increased plasma concentrations and potential toxicity.
* **Corticosteroids:** Increased risk of GI ulceration.
## Monitoring
* **Baseline:** Serum creatinine, LFTs, CBC (if on long-term therapy), blood pressure.
* **Ongoing:** Monitor for signs of GI bleeding (occult blood in stool, anemia), symptoms of fluid retention/edema, and changes in renal function.
## Clinical Pearls
* **Administration:** Take with food or milk to minimize GI irritation.
* **GI Risk:** Mefenamic acid carries a higher risk of diarrhea compared to other NSAIDs.
* **Cardiovascular Warning:** Like all non-aspirin NSAIDs, it increases the risk of serious thrombotic events; use lowest effective dose for the minimum duration required to meet treatment goals.
* **Pregnancy:** Avoid use starting at 20 weeks gestation due to the risk of fetal renal dysfunction leading to oligohydramnios.
***
**Disclaimer:** This information is for educational purposes only. Clinical practice guidelines vary by institution and region. Always verify specific dosing, safety warnings, and contraindications via current, authoritative sources such as the FDA-approved product labeling (package insert) or institutional clinical protocols before prescribing or administering medication.
