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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative class. It has analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea).
* Symptomatic relief of rheumatoid arthritis and osteoarthritis (though other NSAIDs may be preferred due to safety profiles).
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours.
* **Rheumatoid Arthritis/Osteoarthritis:** 750 mg three times daily.
* **Maximum:** Do not exceed 1500 mg per day for pain and dysmenorrhea; up to 2000 mg per day may be used in severe inflammatory conditions under close medical supervision.
## Pediatric Dosing
* Mefenamic acid is generally not recommended for children under 14 years of age for pain relief due to insufficient safety and efficacy data.
* Specific pediatric dosing for other indications is not well-established.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary, especially in severe impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of NSAID-induced bronchospasm, urticaria, or allergic-type reactions.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease (active or history).
* Severe heart failure.
* Severe renal impairment.
* Severe hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation.
* **Serious:**
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and heart failure.
* **Gastrointestinal:** Ulceration, bleeding, perforation.
* **Renal:** Acute kidney injury, interstitial nephritis.
* **Hepatic:** Hepatotoxicity, elevated liver enzymes.
* **Hematologic:** Anemia, prolonged bleeding time.
* **Dermatologic:** Stevens-Johnson syndrome, toxic epidermal necrolysis, exfoliative dermatitis.
* **Hypersensitivity:** Anaphylaxis, asthma exacerbation.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Antiplatelets (e.g., aspirin, clopidogrel):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of GI bleeding.
* **ACE inhibitors, ARBs, diuretics:** May reduce antihypertensive effect and increase risk of renal impairment.
* **Lithium, Methotrexate:** Increased serum levels and toxicity.
## Monitoring
* **Baseline and periodic:** Renal function (creatinine, BUN), liver function tests (ALT, AST), complete blood count (CBC) with differential and platelet count.
* **For chronic use:** Monitor for signs and symptoms of GI bleeding, cardiovascular events, and renal/hepatic dysfunction.
## Clinical Pearls
* Mefenamic acid is typically used for short-term pain management.
* It should be taken with food or milk to minimize GI upset.
* Due to potential serious cardiovascular and GI risks, it should be used at the lowest effective dose for the shortest duration necessary.
* Avoid concomitant use with other NSAIDs.
* Consider alternatives for patients with significant cardiovascular risk factors, renal impairment, or a history of GI issues.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for complete details.*
