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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It acts by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea).
* Rheumatoid arthritis and osteoarthritis (less commonly used due to GI risk).
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed. Maximum daily dose: 1500 mg.
* **Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed. Maximum daily dose: 1500 mg.
## Pediatric Dosing
Mefenamic acid is generally **not recommended** for pediatric use due to lack of established safety and efficacy data, particularly in younger children. Specific dosing is not well-defined.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Reduced doses may be considered, but specific guidelines are lacking. Monitor renal function closely.
* **Hepatic Impairment:** Use with caution. Monitor liver function closely.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs.
* 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 renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include gastrointestinal (GI) disturbances (nausea, vomiting, diarrhea, abdominal pain, dyspepsia), dizziness, and headache. Serious GI events (bleeding, ulceration, perforation) can occur. Other potential adverse effects include rash, fluid retention, hypertension, and renal toxicity.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Other NSAIDs or Aspirin:** Increased risk of GI toxicity and reduced cardioprotective effect of low-dose aspirin.
* **ACE Inhibitors, ARBs, Diuretics:** Reduced antihypertensive effect and increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Monitor renal function (BUN, creatinine) and electrolytes, especially in patients with pre-existing renal disease or those on concomitant nephrotoxic agents.
* Monitor liver function (AST, ALT), especially with long-term use or in patients with hepatic impairment.
* Monitor blood pressure.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize GI upset.
* It is generally recommended for short-term use only due to a higher risk of GI adverse effects compared to some other NSAIDs.
* The onset of analgesia is typically within 1 hour.
* Due to potential for dizziness and drowsiness, advise caution with activities requiring mental alertness.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making treatment decisions. Dosing and recommendations may vary based on patient-specific factors and local protocols.
