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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class, used for the short-term treatment of mild to moderate pain. Its mechanism involves inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Pain, mild to moderate, particularly associated with:
* Primary dysmenorrhea
* Menstrual pain
## Adult Dosing
* **Initial dose:** 500 mg orally every 4 to 6 hours as needed.
* **Maximum daily dose:** 1500 mg.
* **Duration:** Not recommended for use longer than 7 days.
## Pediatric Dosing
* Mefenamic acid is generally **not recommended** for pediatric patients under 14 years of age due to lack of established safety and efficacy data. Some limited data suggests potential use in older adolescents for dysmenorrhea, but this should be guided by specialist advice and local protocols.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe renal impairment, though specific guidelines are lacking due to potential for renal toxicity.
* **Hepatic Impairment:** Use with caution. Monitor liver function closely. Dose adjustment data is limited.
* **Elderly:** Increased risk of adverse effects, particularly gastrointestinal bleeding and renal events. Use the lowest effective dose for the shortest duration.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, asthma, nasal polyps, angioedema, urticaria, or other 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 history of recurrent gastrointestinal bleeding.
* Severe renal impairment.
* Severe hepatic impairment.
* Severe heart failure.
* Pregnancy: Third trimester.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, dyspepsia, constipation, dizziness, headache, rash.
* **Serious:**
* **Gastrointestinal:** Bleeding, ulceration, perforation.
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and heart failure.
* **Renal:** Acute kidney injury, interstitial nephritis, papillary necrosis.
* **Hepatic:** Hepatotoxicity, jaundice.
* **Hematologic:** Anemia, thrombocytopenia, leukopenia.
* **Hypersensitivity:** Anaphylaxis, Stevens-Johnson syndrome, toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of gastrointestinal bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of gastrointestinal, renal, and cardiovascular adverse effects.
* **Diuretics, ACE inhibitors, Angiotensin II Receptor Blockers (ARBs):** May decrease antihypertensive effect and increase risk of renal impairment.
* **Lithium:** May increase serum lithium levels.
* **Methotrexate:** May increase methotrexate toxicity.
## Monitoring
* **Renal function:** Monitor serum creatinine and BUN, especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** Monitor liver enzymes (AST, ALT).
* **Gastrointestinal symptoms:** Assess for signs of bleeding (melena, hematemesis) or ulceration.
* **Blood pressure:** NSAIDs can increase blood pressure.
* **Signs of hypersensitivity.**
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* Administer with food or milk to minimize gastrointestinal upset.
* Due to potential renal toxicity, caution is advised in dehydrated patients, the elderly, and those with pre-existing renal or heart conditions.
* Should be used at the lowest effective dose for the shortest duration necessary to minimize risks.
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*This information is intended for healthcare professionals and does not replace comprehensive prescribing information. Always verify current prescribing information with the latest product monograph or reliable drug reference resources.*
