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# Mefenamic Acid (Meftal-P)
## Overview
Mefenamic acid is a non-steroidal anti-inflammatory drug (NSAID) that exhibits analgesic, anti-inflammatory, and antipyretic properties via the inhibition of cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis.
## Primary Indications
* Primary dysmenorrhea.
* Mild to moderate pain.
* *Note: Use is generally limited to short-term therapy (not exceeding 7 days).*
## Adult Dosing
* **Standard Dose:** 500 mg orally initially, followed by 250 mg every 6 hours as needed.
* **Maximum Dose:** 1500 mg per 24 hours.
## Pediatric Dosing
* **Age ≥ 14 years:** Follow adult dosing guidelines.
* **Age < 14 years:** Safety and efficacy have not been established by controlled clinical trials for routine pediatric use. Dosing is highly dependent on local institutional protocols; consult pediatric-specific formularies.
## Dose Adjustments
* **Renal Impairment:** Avoid in patients with severe renal impairment (CrCl < 30 mL/min). Use with extreme caution and monitor closely in mild to moderate impairment.
* **Hepatic Impairment:** Avoid in patients with severe hepatic impairment. Reduce initial dose in mild to moderate impairment.
* **Geriatric:** Use the lowest effective dose for the shortest duration due to increased risk of gastrointestinal (GI) and cardiovascular toxicity.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs (risk of anaphylaxis/asthma exacerbation).
* History of GI bleeding or perforation related to prior NSAID therapy.
* Active peptic ulcer disease or inflammatory bowel disease.
* Pre-operative period in the setting of coronary artery bypass graft (CABG) surgery.
* Severe renal or hepatic failure.
* Third trimester of pregnancy.
## Adverse Effects
* **Gastrointestinal:** Nausea, vomiting, diarrhea (frequent), abdominal pain, GI ulceration, bleeding.
* **Renal:** Fluid retention, edema, acute renal failure, interstitial nephritis.
* **Cardiovascular:** Hypertension, increased risk of myocardial infarction or stroke (class effect).
* **Hematologic:** Anemia, transient drop in hematocrit.
* **Neurologic:** Drowsiness, dizziness, headache.
## Key Drug Interactions
* **Anticoagulants/Antiplatelets (e.g., Warfarin, Clopidogrel):** Increased risk of bleeding.
* **ACE Inhibitors/ARBs/Diuretics:** Reduced antihypertensive effect and increased risk of acute kidney injury.
* **Lithium:** May increase serum lithium levels (monitor toxicity).
* **Methotrexate:** May increase methotrexate toxicity via decreased renal clearance.
* **Other NSAIDs/Corticosteroids:** Increased risk of GI toxicity.
## Monitoring
* **Baseline/Intermittent:** Serum creatinine, BUN, liver function tests (LFTs), and complete blood count (CBC).
* **Ongoing:** Blood pressure monitoring, assessment for occult or overt GI bleeding, and signs of edema.
## Clinical Pearls
* **GI Protection:** Administer with food or milk to minimize gastric irritation.
* **Duration:** Limit total duration of treatment to no more than 7 days to mitigate the risk of severe adverse effects.
* **Diarrhea:** Mefenamic acid is uniquely associated with diarrhea in some patients; discontinue if severe diarrhea occurs.
* **Cardiovascular Warning:** Like all NSAIDs, it carries a boxed warning for increased risk of serious cardiovascular thrombotic events.
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**Disclaimer:** This information is for educational purposes and does not replace professional clinical judgment. Always consult the most current local prescribing information, package inserts, and hospital guidelines before administering medication.
