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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. 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.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain and bleeding.
* **Maximum Daily Dose:** 1500 mg. Treatment duration should generally not exceed 7 days.
## Pediatric Dosing
Dosing in pediatric patients is not well-established. Use in children under 14 years of age is generally not recommended due to lack of data.
## Dose Adjustments
No specific dose adjustments are required for renal or hepatic impairment. However, caution is advised, and the lowest effective dose should be used, particularly in patients with severe hepatic or renal dysfunction.
## 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.
* Inflammatory bowel disease (Crohn's disease, ulcerative colitis).
* Severe heart failure, severe renal impairment, severe hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, constipation, dizziness, rash, headache.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal toxicity (including interstitial nephritis, papillary necrosis); hepatic toxicity; cardiovascular thrombotic events (myocardial infarction, stroke); bronchospasm; Stevens-Johnson syndrome/toxic epidermal necrolysis.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI adverse effects.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Other NSAIDs/Aspirin:** Increased risk of GI bleeding and renal toxicity.
* **Diuretics/ACE Inhibitors/Angiotensin II Receptor Blockers (ARBs):** Reduced antihypertensive effect; increased risk of renal impairment.
* **Lithium/Methotrexate:** Increased serum levels and toxicity.
## Monitoring
* Signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Renal function (BUN, creatinine) especially in patients with pre-existing renal disease or those at risk.
* Liver function tests (ALT, AST) if liver dysfunction is suspected.
* Blood pressure, especially in patients with hypertension.
## Clinical Pearls
* Administer with food or milk to minimize GI upset.
* Mefenamic acid is for short-term use only (generally less than 7 days).
* Diarrhea is a common and often dose-limiting side effect. Discontinue if severe diarrhea occurs.
* Use with caution in patients with pre-existing cardiovascular disease, hypertension, renal impairment, hepatic impairment, or a history of peptic ulcer disease.
* Avoid concomitant use with other NSAIDs.
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**Disclaimer:** This information is intended for clinical pharmacists and other healthcare professionals. It is essential to consult the most current prescribing information and relevant clinical guidelines for definitive patient care decisions.
