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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term management of mild to moderate pain, particularly menstrual pain. It functions by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Primary Dysmenorrhea:** 500 mg initially, followed by 250 mg every 6 hours as needed.
* **Maximum daily dose:** 1500 mg.
* Treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for pediatric use due to a lack of established safety and efficacy data, particularly concerning the potential for Reye's syndrome in children with viral infections.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose adjustments may be necessary based on renal function, but specific guidelines are not well-established. Generally avoided in severe renal impairment.
* **Hepatic Impairment:** Use with caution. Generally avoided in severe hepatic impairment.
## Contraindications
* Known hypersensitivity to mefenamic acid or other NSAIDs.
* 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 (GI) bleeding or history of recurrent GI ulceration/bleeding.
* Severe renal or hepatic impairment.
* Pregnancy: Contraindicated in the third trimester. Use with caution in the first and second trimesters.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, dyspepsia, constipation, headache.
* **Serious:** GI bleeding, ulceration, perforation; renal failure; hepatic dysfunction; cardiovascular thrombotic events; hypersensitivity reactions; Stevens-Johnson syndrome/toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of GI toxicity and other adverse effects.
* **Diuretics and antihypertensives:** May reduce their efficacy and increase risk of renal impairment.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased methotrexate toxicity.
## Monitoring
* Monitor for signs and symptoms of GI bleeding or ulceration (e.g., melena, hematemesis, abdominal pain).
* Monitor renal and hepatic function, especially in patients with pre-existing impairment or those on long-term therapy.
* Assess for cardiovascular risk factors and signs of cardiovascular events.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* Always administer with food or milk to minimize GI upset.
* Due to a higher incidence of GI side effects, it is often considered less preferable than other NSAIDs for general pain relief.
* The risk of aseptic meningitis has been reported, particularly in patients with systemic lupus erythematosus.
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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 and relevant guidelines before making any clinical decisions.
