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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) with analgesic and anti-inflammatory properties.
## Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain.
* Management of rheumatoid arthritis and osteoarthritis (less commonly used for chronic conditions due to safety profile).
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Do not exceed 1500 mg in any 24-hour period for the first 7 days of treatment, and 1000 mg per day thereafter.
* **Rheumatoid Arthritis/Osteoarthritis:** 750 mg every 6 hours initially, then 500 mg every 6 hours as needed. Do not exceed 1500 mg per day.
## Pediatric Dosing
* **Pain/Inflammation:** Mefenamic acid is generally *not recommended* for use in children under 14 years of age for pain. Some sources suggest dosing for juvenile rheumatoid arthritis, but this is not a primary indication and should be guided by specialist recommendations. Consult specific pediatric formularies or specialist advice for any potential use.
## 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.
* **Elderly:** Increased risk of adverse effects, especially gastrointestinal bleeding and renal dysfunction. Consider lower doses and closer monitoring.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, asthma, rhinitis, or urticaria induced by aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal ulceration or bleeding.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Gastrointestinal upset (nausea, vomiting, diarrhea, abdominal pain), dyspepsia, headache, dizziness, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal toxicity; hepatic toxicity; cardiovascular thrombotic events; exacerbation of asthma; hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of adverse effects, especially gastrointestinal bleeding.
* **Diuretics, ACE Inhibitors, ARBs:** May reduce antihypertensive efficacy and increase risk of renal impairment.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Renal function:** Baseline and periodically, especially in patients with pre-existing renal disease or those on concomitant nephrotoxic agents.
* **Hepatic function:** Baseline and periodically.
* **Gastrointestinal symptoms:** Monitor for signs of bleeding or ulceration.
* **Blood pressure:** NSAIDs can increase blood pressure.
## Clinical Pearls
* Mefenamic acid is typically for short-term use due to a higher risk of gastrointestinal adverse effects compared to some other NSAIDs.
* Administer with food or milk to minimize gastrointestinal upset.
* Ensure adequate hydration.
* Advise patients to report any signs of bleeding (e.g., black tarry stools, vomiting blood) or other serious adverse effects immediately.
* Limited data exists for long-term efficacy and safety in chronic conditions like rheumatoid arthritis.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and local protocols before making clinical decisions.
