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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for mild to moderate pain and menstrual pain. It works by inhibiting prostaglandin synthesis.
## Primary Indications
* Mild to moderate pain
* Primary dysmenorrhea (menstrual pain)
## Adult Dosing
* **Pain:** 500 mg orally every 6 hours as needed.
* **Primary Dysmenorrhea:** 500 mg orally every 6 hours as needed, starting with the onset of pain or bleeding.
* **Maximum Duration:** Typically recommended for no more than 7 days.
* **Maximum Daily Dose:** 1500 mg.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to a risk of serious adverse effects, including an increased risk of nephrotic syndrome.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dosage adjustments may be necessary, though specific guidelines are limited.
* **Hepatic Impairment:** Use with caution. Dosage adjustments may be necessary, though specific guidelines are limited.
## Contraindications
* Hypersensitivity to mefenamic acid or other NSAIDs.
* History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs.
* Peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Inflammatory bowel disease.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include diarrhea, nausea, vomiting, abdominal pain, constipation, and rash. More serious effects can include gastrointestinal bleeding, perforation, peptic ulceration, renal toxicity, cardiovascular thrombotic events, hypersensitivity reactions, and Stevens-Johnson syndrome/toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate levels and toxicity.
* **Diuretics, ACE inhibitors, Angiotensin II Receptor Blockers:** Reduced antihypertensive effect and increased risk of renal impairment.
## Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** If used chronically.
* **Signs of gastrointestinal bleeding:** Stool guaiac, hematemesis, melena.
* **Blood pressure:** NSAIDs can cause hypertension.
## Clinical Pearls
* Mefenamic acid is generally reserved for short-term use due to a higher incidence of gastrointestinal adverse effects compared to some other NSAIDs.
* For dysmenorrhea, it should be initiated at the onset of pain rather than waiting for severe pain.
* Ensure adequate hydration to minimize renal risk.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the official prescribing information and relevant local guidelines for complete and up-to-date information before making any clinical decisions.*
