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 by reversibly inhibiting cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Treatment of primary dysmenorrhea.
* Short-term management of mild to moderate pain (typically not exceeding 7 days).
## Adult Dosing
* **Dysmenorrhea/Pain:** 500 mg orally initially, followed by 250 mg every 6 hours as needed.
* **Maximum Duration:** 7 days.
## Pediatric Dosing
* **Children ≥ 14 years:** Use adult dosing (500 mg initial, 250 mg q6h PRN).
* **Children < 14 years:** Safety and efficacy have not been established. Usage is generally avoided.
## Dose Adjustments
* **Renal Impairment:** Use with caution in patients with preexisting renal disease. Avoid in severe renal impairment (CrCl < 30 mL/min).
* **Hepatic Impairment:** Use caution; lower doses may be required due to extensive hepatic metabolism.
* **Geriatric:** Use the lowest effective dose for the shortest duration due to increased risk of cardiovascular and gastrointestinal events.
## Contraindications
* 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.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Severe renal or hepatic impairment.
## Adverse Effects
* **Gastrointestinal:** Nausea, vomiting, diarrhea (may be severe), abdominal pain, GI ulceration/bleeding.
* **Renal:** Fluid retention, edema, acute renal failure, interstitial nephritis.
* **Hematologic:** Potential for blood dyscrasias, anemia.
* **Dermatologic:** Rash, pruritus, Stevens-Johnson syndrome (rare).
* **General:** Headache, dizziness, blood pressure elevation.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding due to antiplatelet effects and gastric mucosal damage.
* **Other NSAIDs/Aspirin:** Increased risk of GI toxicity and additive renal impairment.
* **ACE Inhibitors/ARBs/Diuretics:** May diminish antihypertensive effects and increase risk of acute renal failure.
* **Lithium/Methotrexate:** Decreased renal clearance, increasing risk of systemic toxicity.
## Monitoring
* **Baseline:** CBC, LFTs, and renal function (BUN/SCr) in patients on chronic therapy.
* **Ongoing:** Blood pressure monitoring, assessment for occult or overt GI bleeding, and signs of edema or weight gain.
* **Specific:** Monitor stool frequency; diarrhea can be a dose-limiting side effect of mefenamic acid specifically.
## Clinical Pearls
* **GI Irritation:** Take with food or milk to minimize gastrointestinal discomfort.
* **Diarrhea:** Distinct from other NSAIDs, mefenamic acid is frequently associated with diarrhea. If diarrhea occurs, the drug should be discontinued promptly.
* **CV Risk:** Like all NSAIDs, it carries a boxed warning for increased risk of serious cardiovascular thrombotic events, including MI and stroke.
* **Prostaglandins:** It is a potent inhibitor of prostaglandin synthesis; avoid use in the third trimester of pregnancy (risk of premature closure of the ductus arteriosus).
***
**Disclaimer:** This information is for educational purposes only. Always verify current prescribing information, contraindications, and drug interactions against local clinical protocols, official package inserts, or trusted clinical decision support tools (e.g., Lexicomp, UpToDate) before prescribing.
