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# Mefenamic acid
## Overview
Mefenamic acid is an anthranilic acid derivative nonsteroidal anti-inflammatory drug (NSAID) that exhibits analgesic, anti-inflammatory, and antipyretic properties via non-selective inhibition of cyclooxygenase (COX-1 and COX-2) enzymes.
## Primary Indications
* Treatment of mild to moderate pain.
* Treatment of primary dysmenorrhea.
* *Note:* Use is limited to short-term duration (≤ 7 days).
## Adult Dosing
* **Pain/Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum:** Do not exceed 1 week of therapy.
## Pediatric Dosing
* **Children ≥ 14 years:** Use adult dosing regimen.
* **Children < 14 years:** Safety and efficacy have not been established. Use is generally not recommended.
## Dose Adjustments
* **Renal Impairment:** Avoid in patients with severe renal impairment. Use with caution in mild-to-moderate impairment; close monitoring of renal function is required.
* **Hepatic Impairment:** Use with caution; monitor for signs of hepatotoxicity. Avoid in severe hepatic impairment.
* **Geriatric:** Use the lowest effective dose for the shortest duration due to increased risk of gastrointestinal (GI) toxicity and renal complications.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin/NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active peptic ulcer disease or history of GI bleeding.
* Severe renal or hepatic failure.
## Adverse Effects
* **Gastrointestinal:** Nausea, vomiting, diarrhea (may be severe), abdominal pain, dyspepsia.
* **Cardiovascular:** Fluid retention, edema, increased risk of thrombotic events, hypertension.
* **Renal:** Acute kidney injury, interstitial nephritis, hyperkalemia.
* **Hematologic:** Anemia, rare cases of agranulocytosis or thrombocytopenia.
## Key Drug Interactions
* **Anticoagulants (e.g., Warfarin):** Increased risk of bleeding.
* **Antiplatelets/SSRIs/SNRIs:** Increased risk of GI bleeding.
* **Antihypertensives (ACE inhibitors, ARBs, Beta-blockers, Diuretics):** May reduce antihypertensive efficacy and increase risk of renal impairment.
* **Lithium:** May increase plasma concentrations of lithium.
* **Methotrexate:** May increase methotrexate toxicity.
## Monitoring
* Baseline and periodic monitoring of renal function (BUN/SCr).
* Monitor for signs of GI bleeding (black stools, hematemesis).
* Blood pressure monitoring, especially in patients with hypertension.
* Complete blood count (CBC) if long-term use is inadvertent.
## Clinical Pearls
* **Administration:** Should be taken with food or milk to minimize GI irritation.
* **GI Caution:** Mefenamic acid is associated with a higher incidence of diarrhea compared to other NSAIDs.
* **CV Warning:** All NSAIDs (except aspirin) carry a boxed warning for increased risk of serious cardiovascular thrombotic events (myocardial infarction, stroke).
* **Hydration:** Ensure adequate hydration to prevent renal complications.
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*Disclaimer: This information is for educational purposes only and does not constitute medical advice. Consult current prescribing information (e.g., FDA labels or local institutional guidelines) and verify all doses before prescribing or administering medication.*
