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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term relief of mild to moderate pain, including menstrual pain.
## Primary Indications
* Pain, mild to moderate, including dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, typically started at the onset of pain and bleeding.
* **Maximum Dose:** Not to exceed 1000 mg as a single dose or 4000 mg in 24 hours. Treatment duration should be limited to 7 days.
## Pediatric Dosing
* Mefenamic acid is **not recommended for use in children under 14 years of age** due to lack of established safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustments are established, but NSAIDs can precipitate renal failure. Monitor renal function closely.
* **Hepatic Impairment:** Use with caution. No specific dose adjustments are established, but NSAIDs can cause liver dysfunction. Monitor liver function.
## 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.
* Active gastrointestinal (GI) bleeding or a history of recurrent GI ulceration or hemorrhage.
* Severe heart failure.
* Severe renal impairment.
* Severe hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain, dyspepsia, constipation, rash.
* **Serious:** Gastrointestinal bleeding, ulceration, perforation; renal toxicity (including interstitial nephritis, papillary necrosis, renal failure); cardiovascular thrombotic events (myocardial infarction, stroke); hepatic reactions (hepatitis, jaundice); hypersensitivity reactions, Stevens-Johnson syndrome, toxic epidermal necrolysis; exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate levels and toxicity.
* **Diuretics, ACE inhibitors, Angiotensin II Receptor Blockers (ARBs):** May decrease antihypertensive effect and increase risk of renal damage.
* **Other NSAIDs/Aspirin:** Increased risk of GI adverse effects and potential for additive effects.
## Monitoring
* **GI symptoms:** Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* **Renal function:** Monitor serum creatinine and BUN, especially in patients with pre-existing renal disease or those at risk for renal impairment.
* **Hepatic function:** Monitor liver enzymes (ALT, AST) in patients with known liver disease or those receiving long-term therapy.
* **Blood pressure:** Monitor blood pressure, as NSAIDs can cause or exacerbate hypertension.
## Clinical Pearls
* Mefenamic acid is generally intended for short-term use only.
* Administer with food or milk to minimize GI upset.
* Diarrhea is a relatively common adverse effect and may necessitate discontinuation.
* Due to NSAID class effects, consider risks of cardiovascular thrombotic events, GI bleeding, renal, and hepatic toxicity.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions. Local protocols may vary.
