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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative class. It inhibits cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term relief of mild to moderate pain, including menstrual pain (dysmenorrhea), headache, dental pain, and musculoskeletal pain.
* Management of pain and inflammation associated with rheumatoid arthritis and osteoarthritis (though not a preferred agent for chronic conditions).
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed. Maximum daily dose is 1500 mg (for short-term use only).
* **Dysmenorrhea:** 500 mg as the first dose, followed by 250 mg every 6 hours as needed.
* **Rheumatoid Arthritis/Osteoarthritis:** 500 mg three times daily.
## Pediatric Dosing
* Mefenamic acid is generally **not recommended** for use in children under 14 years of age due to limited safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary, particularly in severe impairment. Monitor renal function closely.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary. Monitor liver function.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal toxicity. Consider lower doses and closer monitoring.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, asthma, allergic rhinitis, or urticaria precipitated by aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active peptic ulceration or gastrointestinal bleeding.
* Severe renal or hepatic impairment.
* Severe heart failure.
* Pregnancy (third trimester).
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, dizziness, headache.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal failure; hepatic failure; hypersensitivity reactions (including Stevens-Johnson syndrome, toxic epidermal necrolysis); bronchospasm; exacerbation of asthma; fluid retention; hypertension.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Antiplatelets (e.g., aspirin, clopidogrel):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Diuretics, ACE inhibitors, ARBs:** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium:** Increased lithium levels, potentially leading to toxicity.
* **Methotrexate:** Increased methotrexate levels and toxicity.
* **Other NSAIDs:** Increased risk of adverse effects, particularly gastrointestinal.
## Monitoring
* **Gastrointestinal:** Monitor for signs and symptoms of bleeding (e.g., melena, hematemesis, abdominal pain).
* **Renal:** Monitor renal function (BUN, creatinine) especially in patients with pre-existing renal disease, dehydration, or those taking concomitant nephrotoxic agents.
* **Hepatic:** Monitor liver function tests (ALT, AST) periodically, especially with prolonged use.
* **Cardiovascular:** Assess for signs of cardiovascular events.
* **Blood Pressure:** Monitor blood pressure, as NSAIDs can cause fluid retention and hypertension.
## Clinical Pearls
* Mefenamic acid is for **short-term use only** due to a higher risk of gastrointestinal toxicity compared to other NSAIDs.
* Onset of pain relief is typically within 1 hour.
* Administer with food or milk to minimize gastrointestinal upset.
* Avoid concurrent use with other NSAIDs or aspirin.
* Due to potential for dizziness, advise patients to exercise caution when driving or operating machinery.
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*This information is intended for healthcare professionals. Please consult the most current prescribing information and local guidelines for complete details.*
