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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It acts by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 to 8 hours as needed. Maximum daily dose is 1500 mg. Therapy should not exceed 7 days.
* **Dysmenorrhea:** 500 mg every 6 to 8 hours starting with the onset of pain or bleeding and continuing for the duration of symptoms, up to 7 days.
## Pediatric Dosing
Mefenamic acid is **not recommended** for use in children under 14 years of age for over-the-counter indications. Safety and efficacy in pediatric patients for prescription indications are not established by all regulatory bodies. Limited data suggests doses of 6.5 mg/kg every 6-8 hours may be used in children aged 6 months and older for pain, but this requires careful consideration of risks and benefits.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe impairment.
## 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 impairment.
* Severe hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include diarrhea, nausea, vomiting, abdominal pain, constipation, dyspepsia, headache, and dizziness. Serious adverse effects can include gastrointestinal bleeding, ulceration, perforation, cardiovascular thrombotic events, myocardial infarction, stroke, renal failure, hepatic failure, and hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of adverse effects, particularly gastrointestinal.
* **Diuretics and antihypertensives:** May reduce diuretic and antihypertensive efficacy and increase risk of renal impairment.
* **Lithium:** Increased lithium levels.
* **Methotrexate:** Increased methotrexate toxicity.
## Monitoring
* Monitor for signs and symptoms of gastrointestinal bleeding and ulceration.
* Monitor renal and hepatic function, especially in patients with pre-existing impairment or those on long-term therapy.
* Monitor blood pressure.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* It should be taken with food or milk to minimize gastrointestinal upset.
* Due to a higher incidence of diarrhea, it may not be the preferred NSAID in all patients.
* Risk of serious cardiovascular thrombotic events, myocardial infarction, and stroke may increase with duration of use.
**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant literature for complete details and to verify dosing and safety before initiating therapy.
