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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative 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, including menstrual pain (dysmenorrhea), headache, dental pain, and musculoskeletal pain.
* Management of inflammatory conditions.
## Adult Dosing
* **Pain:** 500 mg every 6 to 8 hours as needed. Maximum daily dose is 1500 mg.
* **Dysmenorrhea:** 500 mg every 6 to 8 hours as needed, usually starting with the onset of pain or bleeding.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age for over-the-counter use. For prescription use, dosing varies significantly by indication and weight. Consult specific pediatric guidelines or a specialist.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Mefenamic acid is largely excreted by the kidneys. Dose reduction may be necessary in severe renal impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe hepatic impairment.
* **Elderly:** Elderly patients may be at increased risk of adverse effects, particularly gastrointestinal bleeding and renal toxicity. Use the lowest effective dose for the shortest duration.
## Contraindications
* Known hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* History of asthma, urticaria, or 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 ulceration.
* Severe renal or hepatic impairment.
* Severe heart failure.
## Adverse Effects
Common adverse effects include nausea, vomiting, diarrhea, abdominal pain, constipation, and dizziness. More serious adverse effects include:
* **Gastrointestinal:** Gastric irritation, ulceration, bleeding, perforation.
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and heart failure.
* **Renal:** Renal impairment, interstitial nephritis, papillary necrosis.
* **Hepatic:** Hepatitis, jaundice.
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Hypersensitivity:** Rash, pruritus, 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.
* **Other NSAIDs/Aspirin:** Increased risk of adverse effects, particularly gastrointestinal.
* **ACE Inhibitors/ARBs:** May reduce antihypertensive effect and increase risk of renal impairment.
* **Diuretics:** May reduce diuretic effect and increase risk of renal impairment.
* **Lithium:** Mefenamic acid can increase lithium levels, potentially leading to toxicity.
* **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, especially with prolonged use.
* **Gastrointestinal symptoms:** Advise patients to report any signs of bleeding (e.g., black tarry stools, hematemesis).
* **Blood pressure:** Monitor blood pressure, particularly in patients taking antihypertensives.
* **Signs of hypersensitivity:** Monitor for rash or other allergic reactions.
## Clinical Pearls
* Administer with food or milk to minimize gastrointestinal upset.
* Short-term use is generally recommended due to potential for serious adverse effects with prolonged use.
* Consider gastroprotective agents (e.g., PPIs) for patients at high risk of GI bleeding.
* Avoid in patients with a history of NSAID-induced bronchospasm.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information or a qualified healthcare provider for diagnosis and treatment. Dosing and recommendations may vary based on patient-specific factors and local protocols.
