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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties, primarily through the inhibition of 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. Maximum daily dose: 1500 mg.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, initiated at the onset of pain and bleeding, and continued for the duration of symptoms. Maximum daily dose: 1500 mg.
* Treatment duration should be limited to a maximum of 7 days.
## Pediatric Dosing
Mefenamic acid is generally **not recommended** for use in pediatric patients under 14 years of age for over-the-counter indications. Specific indications and dosing for pediatric patients in prescription settings may exist but require careful consideration of risks and benefits.
## Dose Adjustments
No specific dose adjustments are required for renal or hepatic impairment, but caution is advised. Use the lowest effective dose for the shortest duration necessary.
## 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 (e.g., Crohn's disease, ulcerative colitis).
* Significant renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
Common:
* Gastrointestinal upset (nausea, vomiting, diarrhea, abdominal pain, constipation)
* Dizziness, drowsiness
* Headache
Serious:
* Gastrointestinal bleeding, ulceration, perforation
* Cardiovascular thrombotic events (myocardial infarction, stroke)
* Renal toxicity (including interstitial nephritis, papillary necrosis)
* Hepatic toxicity
* Hypersensitivity reactions (including anaphylaxis)
* 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.
* **Aspirin:** May decrease the antiplatelet effect of low-dose aspirin and potentially increase gastrointestinal adverse effects.
* **Diuretics, ACE inhibitors, ARBs:** May reduce antihypertensive efficacy and increase risk of renal impairment.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* Signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis).
* Renal function (especially in patients with pre-existing renal disease or risk factors).
* Liver function tests (especially with long-term use or in patients with liver disease).
* Blood pressure.
* Signs of cardiovascular events.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* It is generally recommended for short-term use only due to the risk of serious adverse effects, particularly gastrointestinal and cardiovascular events.
* The risk of gastrointestinal bleeding increases with dose and duration of therapy.
* Use with caution in elderly patients, those with a history of peptic ulcer disease, or those taking anticoagulants.
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*This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions.*
