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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term symptomatic treatment of mild to moderate pain in adults and children over 12 years of age. It is also used for primary dysmenorrhea.
## Primary Indications
* Mild to moderate pain (e.g., dental pain, musculoskeletal pain)
* Primary dysmenorrhea
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg. Treatment duration typically should not exceed 7 days.
* **Primary Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain and continuing for the duration of the symptoms.
## Pediatric Dosing
* **Children 12 years and older:** Dosing is the same as for adults: 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg. Treatment duration typically should not exceed 7 days.
* **Children younger than 12 years:** Safety and efficacy have not been established.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustment guidelines are established, but dose reduction may be considered in severe impairment.
* **Hepatic Impairment:** Use with caution. No specific dose adjustment guidelines are established, but dose reduction may be considered 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.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal (GI) bleeding or ulceration.
* Severe renal or hepatic impairment.
## Adverse Effects
Common adverse effects include:
* GI disturbances: Diarrhea (most common), nausea, vomiting, abdominal pain, constipation, dyspepsia.
* Headache, dizziness.
* Drowsiness.
* Rash.
* Fluid retention and edema.
Serious adverse effects include:
* GI ulceration, bleeding, and perforation.
* Cardiovascular thrombotic events (e.g., myocardial infarction, stroke).
* Renal papillary necrosis and other renal injury.
* Hepatic impairment.
* Hypersensitivity reactions, including anaphylaxis.
* 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) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Other NSAIDs (including aspirin):** Increased risk of GI adverse effects and potential for reduced cardioprotective effects of low-dose aspirin.
* **Diuretics and Antihypertensives (e.g., ACE inhibitors, ARBs, beta-blockers):** NSAIDs can reduce their antihypertensive effect and increase the risk of renal impairment.
* **Lithium:** NSAIDs can increase serum lithium levels.
* **Methotrexate:** NSAIDs can increase methotrexate toxicity.
* **Digoxin:** NSAIDs can increase serum digoxin levels.
* **Cyclosporine:** Increased risk of nephrotoxicity.
## Monitoring
* Monitor for signs and symptoms of GI bleeding (e.g., melena, hematemesis).
* Monitor for signs and symptoms of cardiovascular events.
* Monitor renal and hepatic function, especially in patients with pre-existing impairment or those on long-term therapy.
* Monitor for signs of hypersensitivity reactions.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize GI upset.
* Due to the potential for diarrhea, it is generally recommended for short-term use only (not exceeding 7 days).
* The highest incidence of GI side effects occurs with prolonged use.
* Consider alternative analgesics if GI intolerance develops.
* Advise patients to avoid concomitant use with other NSAIDs.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the current prescribing information and your institution's protocols before making any clinical decisions.
