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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 6 hours as needed.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, typically initiated at the onset of pain and bleeding and continued for up to 3 days.
* **Maximum:** 1500 mg per day. Duration of use should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for use in children under 14 years of age due to concerns regarding potential serious adverse effects, particularly gastrointestinal bleeding and renal toxicity. Limited data exists for pediatric use, and if used, it should be under strict medical supervision.
## Dose Adjustments
No specific dose adjustments are routinely recommended for renal or hepatic impairment, but caution is advised, and dose reduction may be considered in severe cases due to the potential for NSAID-related toxicity.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* History of gastrointestinal bleeding or perforation related to prior NSAID use.
* Active peptic ulceration or history of recurrent peptic ulceration.
* Severe heart failure.
* Severe renal impairment (creatinine clearance <30 mL/min).
* Severe hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, headache, dizziness, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal toxicity (including interstitial nephritis, papillary necrosis); hepatic toxicity; cardiovascular thrombotic events (MI, stroke); hypersensitivity reactions; Stevens-Johnson syndrome/toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Other NSAIDs and Aspirin:** Increased risk of gastrointestinal bleeding and reduced efficacy of low-dose aspirin cardioprotection.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **ACE Inhibitors, Angiotensin II Receptor Blockers (ARBs), Diuretics:** Reduced antihypertensive efficacy and increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels and risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Gastrointestinal:** Monitor for signs and symptoms of bleeding (e.g., melena, hematemesis).
* **Renal:** Monitor renal function, especially in patients with pre-existing renal disease or those at risk for renal toxicity.
* **Hepatic:** Monitor liver function tests, especially in patients with pre-existing hepatic disease or those on long-term therapy.
* **Cardiovascular:** Assess for signs of cardiovascular events.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Due to potential for serious adverse effects, it should be used at the lowest effective dose for the shortest duration necessary.
* It is not a substitute for aspirin in the prevention of cardiovascular disease.
* Consider gastroprotective agents (e.g., PPIs) in patients with increased risk of GI complications.
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*This information is intended for healthcare professionals and does not substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before making treatment decisions.*
