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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It functions by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed. Do not exceed 1500 mg in the first 24 hours of treatment, and no more than 1000 mg in any 24-hour period thereafter. Treatment duration typically limited to 7 days.
* **Dysmenorrhea:** 500 mg as the initial dose, followed by 250 mg every 6 hours as needed.
## Pediatric Dosing
Mefenamic acid is **not recommended for use in pediatric patients** due to insufficient safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but severe impairment may warrant dose reduction or avoidance.
* **Hepatic Impairment:** Use with caution. Data is limited, but severe impairment may warrant dose reduction or avoidance.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, constipation, headache, dizziness, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal toxicity (including interstitial nephritis, papillary necrosis); cardiovascular thrombotic events (MI, stroke); hepatic toxicity; hypersensitivity reactions; Stevens-Johnson syndrome/toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Other NSAIDs/Aspirin:** Increased risk of adverse effects.
* **Diuretics/ACE Inhibitors/ARBs:** Reduced antihypertensive effect and increased risk of renal impairment.
## Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease or risk factors.
* **Hepatic function:** Especially in patients with pre-existing hepatic disease or risk factors.
* **Signs and symptoms of GI bleeding:** Melena, hematemesis, abdominal pain.
* **Blood pressure:** Monitor for potential increases.
## Clinical Pearls
* Mefenamic acid should be used at the lowest effective dose for the shortest duration necessary to control symptoms.
* It should be taken with food or milk to minimize gastrointestinal upset.
* Due to its potential for GI side effects, it is generally not preferred for chronic pain management.
* The maximum daily dose should not be exceeded due to increased risk of adverse events.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical judgment. Always consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions.*
