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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 functions by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
### Primary Indications
* Pain, particularly associated with menstruation (dysmenorrhea).
* Mild to moderate pain from other causes.
### Adult Dosing
* **Initial dose:** 500 mg orally every 8 hours.
* **Maximum daily dose:** 1500 mg.
* **Duration:** Generally not recommended for use for more than 7 consecutive days.
### Pediatric Dosing
Mefenamic acid is **not generally recommended for use in children under 14 years of age** due to limited data on efficacy and safety. When used in children 14 years and older, adult dosing guidelines typically apply.
### Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustments are established, but reduced efficacy or increased risk of adverse effects may occur.
* **Hepatic Impairment:** Use with caution. No specific dose adjustments are established, but reduced efficacy or increased risk of adverse effects may occur.
### Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* History of bronchospasm, asthma, allergic rhinitis, or urticaria precipitated by aspirin or other NSAIDs.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or a history of recurrent GI ulceration or bleeding.
* Severe renal or hepatic impairment.
* Severe heart failure.
* Late pregnancy (third trimester).
### Adverse Effects
Common adverse effects include: diarrhea, nausea, vomiting, abdominal pain, headache, dizziness, and rash.
More serious adverse effects include:
* **GI:** Gastric or duodenal ulcers, bleeding, perforation.
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, hypertension.
* **Renal:** Renal papillary necrosis, interstitial nephritis, nephrotic syndrome, renal failure.
* **Hepatic:** Hepatotoxicity, elevated liver enzymes.
* **Hematologic:** Anemia, thrombocytopenia.
* **Hypersensitivity:** Anaphylaxis, angioedema.
### Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) & Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of bleeding.
* **Lithium:** Increased serum lithium levels, potentially leading to toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Diuretics & Antihypertensives:** May decrease efficacy and increase risk of renal toxicity.
* **Other NSAIDs (including aspirin):** Increased risk of adverse effects, particularly GI toxicity.
### Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** Especially in patients with pre-existing hepatic disease or those at risk.
* **Signs and symptoms of GI bleeding:** Such as melena, hematemesis, or abdominal pain.
* **Blood pressure:** NSAIDs can cause or exacerbate hypertension.
* **Signs of hypersensitivity reactions.**
### Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize GI upset.
* Due to the risk of diarrhea, it is typically recommended for short-term use only.
* It is generally not preferred over other NSAIDs for chronic inflammatory conditions.
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*This information is intended for clinical use and does not substitute for professional medical advice. Always verify current prescribing information with the official product labeling or a reliable drug information resource before making any clinical decisions.*
