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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. It is a weak acid and is absorbed from the gastrointestinal tract.
## Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea).
## Adult Dosing
* **Pain:** 500 mg orally every 6 hours as needed.
* **Dysmenorrhea:** 500 mg orally every 6 hours as needed, starting at the onset of pain or bleeding.
* **Maximum Daily Dose:** 1500 mg.
* **Duration of Use:** Not recommended for use longer than 7 days.
## Pediatric Dosing
* **Children 12 years and older:** Dosing is the same as for adults.
* **Children younger than 12 years:** Safety and efficacy have not been established.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be considered in severe impairment, but specific guidelines are lacking.
* **Hepatic Impairment:** Use with caution. Specific dose adjustments are not established, but monitoring for liver function is advised.
## Contraindications
* 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 bleeding or history of recurrent GI ulceration or bleeding.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia.
* **Serious:**
* Cardiovascular thrombotic events (myocardial infarction, stroke).
* Gastrointestinal bleeding, ulceration, and perforation.
* Renal toxicity (acute kidney injury, interstitial nephritis).
* Hepatotoxicity.
* Hypersensitivity reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis.
* Fluid retention and edema.
* Worsening of asthma in aspirin-sensitive patients.
## 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 adverse effects, particularly GI bleeding.
* **Diuretics:** Reduced diuretic efficacy and increased risk of renal toxicity.
* **ACE inhibitors and ARBs:** Increased risk of renal impairment.
* **Lithium:** Increased serum lithium levels and risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Renal function:** Monitor periodically, especially in patients with pre-existing renal disease or those at risk for renal impairment.
* **Liver function:** Monitor periodically, especially in patients with pre-existing liver disease or those at risk for hepatotoxicity.
* **Signs and symptoms of GI bleeding:** Monitor for occult blood in stool, abdominal pain, hematemesis, or melena.
* **Blood pressure:** NSAIDs can cause new-onset hypertension or worsen existing hypertension.
## Clinical Pearls
* Mefenamic acid is generally recommended for short-term use only due to the risk of adverse effects, particularly GI issues.
* Administer with food or milk to minimize gastrointestinal upset.
* Avoid in patients with a history of NSAID-induced asthma or hypersensitivity.
* Due to potential for drowsiness, caution patients about activities requiring mental alertness.
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*Disclaimer: This information is intended for clinical use and does not replace professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before making treatment decisions.*
