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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term treatment of mild to moderate pain. It is a weak inhibitor of cyclooxygenase (COX) enzymes.
## Primary Indications
* Pain, mild to moderate (e.g., dysmenorrhea, headache, toothache, musculoskeletal pain).
## Adult Dosing
* **Pain:** 500 mg orally every 4 to 6 hours as needed.
* **Maximum Daily Dose:** 1500 mg.
* **Duration:** Not intended for long-term use; typically limited to 7 days.
## Pediatric Dosing
* **Pain:** Generally not recommended for pediatric patients under 14 years of age. Dosing in children 14 years and older is the same as adults.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustment guidelines are established, but NSAIDs can worsen renal function.
* **Hepatic Impairment:** Use with caution. No specific dose adjustment guidelines are established.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, 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.
* Active gastrointestinal bleeding or ulceration.
* Severe renal or hepatic impairment.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (MI, stroke); renal papillary necrosis and other renal injury; hepatic injury; hypersensitivity reactions (including anaphylaxis and Stevens-Johnson syndrome); bronchospasm.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **SSRIs/SNRIs:** Increased risk of bleeding, especially in the gastrointestinal tract.
* **Other NSAIDs (including aspirin):** Increased risk of adverse effects, particularly gastrointestinal bleeding.
* **ACE Inhibitors/ARBs:** May reduce antihypertensive effect and increase risk of renal impairment.
* **Diuretics:** May reduce diuretic effect and increase risk of renal impairment.
* **Lithium:** May increase lithium levels.
* **Methotrexate:** May increase methotrexate levels and toxicity.
## Monitoring
* Signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis).
* Renal function (e.g., serum creatinine, BUN), especially in patients with pre-existing renal disease or those at risk.
* Hepatic function, particularly with prolonged use.
* Blood pressure, as NSAIDs can increase blood pressure.
## Clinical Pearls
* Mefenamic acid is typically used for short-term pain relief only.
* Administer with food or milk to minimize gastrointestinal upset.
* Monitor for signs of fluid retention and edema, especially in patients with heart failure.
* Discontinue use if any signs of serious adverse effects (e.g., GI bleeding, skin rash, hepatic dysfunction) occur.
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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 relevant clinical guidelines before making any treatment decisions.
