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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term relief of mild to moderate pain. It functions by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Pain (short-term, mild to moderate)
* Primary dysmenorrhea
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose: 1500 mg. Treatment should not exceed 7 days.
* **Primary Dysmenorrhea:** 500 mg every 6 hours starting at the onset of pain or bleeding and continuing for no more than 6 days.
## Pediatric Dosing
Mefenamic acid is generally **not recommended** for pediatric patients under 14 years of age due to a lack of established safety and efficacy data.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, however, caution is advised and lower doses may be considered in patients with severe impairment due to potential accumulation.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of bronchospasm, asthma, allergic rhinitis, or urticaria triggered by aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or history of GI bleeding, ulceration, or perforation.
* Severe heart failure.
* Severe renal impairment.
* Severe hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, headache, dizziness, rash.
* **Serious:**
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and heart failure.
* **Gastrointestinal:** GI bleeding, ulceration, perforation.
* **Renal:** Acute kidney injury, interstitial nephritis.
* **Hepatic:** Liver failure.
* **Hematologic:** Anemia.
* **Dermatologic:** Stevens-Johnson syndrome, toxic epidermal necrolysis.
* **Hypersensitivity:** Anaphylaxis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Aspirin:** May decrease the cardioprotective effect of low-dose aspirin and increase GI risk.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Diuretics:** Reduced diuretic effect; increased risk of nephrotoxicity.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **SSRIs/SNRIs:** Increased risk of GI bleeding.
## Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Monitor for signs of cardiovascular events (e.g., chest pain, shortness of breath).
* Monitor renal function (BUN, creatinine) and liver function tests (LFTs), especially in patients with pre-existing impairment or those on long-term therapy.
* Monitor for signs of hypersensitivity reactions.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize GI upset.
* Due to the risk of serious GI events, use for the shortest duration necessary.
* Consider alternatives for patients with a history of peptic ulcer disease or GI bleeding.
* Avoid concomitant use with other NSAIDs.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the current prescribing information and relevant clinical guidelines for complete and up-to-date information before making any treatment decisions.
