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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for short-term management of mild to moderate pain. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Pain, mild to moderate
* Menstrual pain (dysmenorrhea)
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose: 1500 mg. Duration of use typically limited to 7 days.
* **Dysmenorrhea:** 500 mg every 6 hours starting at the onset of pain, cramping, and/or bleeding.
## Pediatric Dosing
* Mefenamic acid is generally **not recommended** for children under 14 years of age for over-the-counter use. Dosing in pediatric populations for prescription indications should be based on physician guidance and clinical assessment.
## Dose Adjustments
* **Renal impairment:** Use with caution. Reduced doses may be necessary in severe impairment.
* **Hepatic impairment:** Use with caution. Reduced doses may be necessary in severe 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.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, constipation, dyspepsia, headache.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; cardiovascular thrombotic events (myocardial infarction, stroke); renal failure; hepatic failure; hypersensitivity reactions; 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) / Serotonin Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of gastrointestinal bleeding.
* **Lithium:** Increased lithium levels.
* **Methotrexate:** Increased methotrexate levels and toxicity.
* **Diuretics, ACE inhibitors, Angiotensin II Receptor Blockers (ARBs):** Reduced antihypertensive effect and increased risk of renal impairment.
## Monitoring
* **GI symptoms:** Monitor for signs and symptoms of bleeding or ulceration.
* **Renal function:** Assess periodically, especially in patients with risk factors.
* **Hepatic function:** Assess periodically, especially in patients with pre-existing liver disease.
* **Blood pressure:** Monitor for potential increase.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* It is intended for short-term use only (typically no more than 7 days).
* Due to the risk of diarrhea, which can lead to dehydration, patients should be advised to discontinue use and seek medical attention if severe diarrhea occurs.
* Always consider the risk of serious cardiovascular and gastrointestinal events associated with NSAID use.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant literature before making clinical decisions.*
