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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) from the fenamate class. It exhibits analgesic, anti-inflammatory, and antipyretic properties through the inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Primary dysmenorrhea.
## Adult Dosing
Initiate with 500 mg every 4-6 hours as needed. Maximum daily dose is 1500 mg. Treatment duration should generally not exceed 7 days.
## Pediatric Dosing
* For patients ≥ 14 years of age: Dosing is the same as adults (500 mg every 4-6 hours as needed, max 1500 mg/day).
* For patients < 14 years of age: Safety and efficacy have not been established. Consult specific pediatric guidelines if considering use outside of age 14 and above.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, but caution is advised. Mefenamic acid is contraindicated in severe renal or hepatic impairment.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, 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.
* Severe renal impairment.
* Severe hepatic impairment.
* Severe heart failure.
* History of gastrointestinal bleeding or perforation related to previous NSAID use.
* Inflammatory bowel disease.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include diarrhea, nausea, vomiting, abdominal pain, constipation, dizziness, and rash. Serious adverse effects can include gastrointestinal bleeding/perforation, cardiovascular thrombotic events, renal failure, hepatic failure, and hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding. Monitor INR closely.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of gastrointestinal bleeding.
* **Other NSAIDs/Aspirin:** Increased risk of gastrointestinal toxicity and bleeding.
* **Diuretics and Antihypertensives (e.g., ACE inhibitors, ARBs, beta-blockers):** May attenuate antihypertensive effects and increase risk of renal impairment.
* **Lithium:** Increased lithium levels and toxicity. Monitor lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **GI symptoms:** Monitor for signs of bleeding or perforation (e.g., melena, hematemesis).
* **Renal function:** Monitor BUN and creatinine, especially in patients with pre-existing renal disease or those receiving concomitant nephrotoxic agents.
* **Hepatic function:** Monitor liver enzymes periodically.
* **Cardiovascular risk:** Assess for signs of cardiovascular events.
* **Blood pressure:** Monitor for potential increases in blood pressure.
## Clinical Pearls
* Due to a higher incidence of gastrointestinal side effects, mefenamic acid should ideally be used for the shortest duration necessary.
* Administer with food or milk to minimize gastrointestinal upset.
* Should not be used long-term for chronic conditions.
* Considered less potent than other NSAIDs for certain inflammatory conditions but has good analgesic properties.
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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 treatment decisions.
