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## Mefenamic Acid
### Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It is a non-selective COX inhibitor that works by reducing hormones that cause inflammation and pain in the body.
### Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea).
* Management of pain associated with osteoarthritis and rheumatoid arthritis (less commonly used for this indication due to GI risks).
### Adult Dosing
* **Pain:** 500 mg orally every 6 hours as needed.
* **Dysmenorrhea:** 500 mg orally every 6 hours starting at the onset of pain and bleeding, continuing for up to 3 days.
* **Maximum Dose:** Not to exceed 1500 mg in a 24-hour period.
### Pediatric Dosing
* Mefenamic acid is **not generally recommended** for children under 14 years of age due to potential for serious adverse effects and lack of established pediatric dosing guidelines. Specific pediatric use should be guided by a specialist.
### Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe impairment.
### Contraindications
* Hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* 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:** Diarrhea, nausea, vomiting, abdominal pain, constipation, dyspepsia, headache, dizziness.
* **Serious:** Gastrointestinal bleeding, ulceration, and perforation; cardiovascular thrombotic events (MI, stroke); renal failure; hepatic failure; hypersensitivity reactions (including Stevens-Johnson syndrome and toxic epidermal necrolysis); exacerbation of asthma; blood dyscrasias.
### Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **ACE inhibitors, ARBs, Diuretics:** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium:** Increased lithium levels, potentially to toxic levels.
* **Methotrexate:** Increased methotrexate toxicity.
* **Other NSAIDs or Salicylates:** Increased risk of adverse effects, particularly GI.
### Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Monitor renal function (BUN, creatinine) especially in patients with pre-existing renal disease or those on concomitant nephrotoxic agents.
* Monitor liver function tests (ALT, AST) periodically.
* Assess for signs of cardiovascular events.
* Monitor for hypersensitivity reactions.
### Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Due to potential for diarrhea, it is often recommended for short-term use only (e.g., up to 7 days).
* Avoid concomitant use with other NSAIDs.
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**Disclaimer:** This information is for educational purposes and does not substitute for professional medical advice. Always consult with a qualified healthcare provider to ensure the appropriateness and safety of any medication for a specific patient. Always verify current prescribing information.
