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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties. The exact mechanism of action is not fully understood but is believed to involve inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea) and pain associated with dental procedures or musculoskeletal disorders.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 4 to 6 hours as needed. Do not exceed 1500 mg in a 24-hour period.
* **Dysmenorrhea:** 500 mg every 4 to 6 hours as needed, starting at the onset of pain and bleeding.
## Pediatric Dosing
Mefenamic acid is **not generally recommended for use in children under 14 years of age** due to limited safety and efficacy data in this population.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but dose reduction may be necessary in severe impairment. Avoid in severe renal disease.
* **Hepatic Impairment:** Use with caution. Data is limited, but dose reduction may be necessary in severe impairment. Avoid in severe hepatic disease.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, other NSAIDs, or any component of the formulation.
* 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 ulceration.
* Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis) in the active state.
* Severe heart failure, renal impairment, or hepatic impairment.
* Pregnancy, particularly in the third trimester.
## Adverse Effects
Common adverse effects include gastrointestinal upset (nausea, vomiting, diarrhea, abdominal pain, dyspepsia), dizziness, headache, and rash.
Serious adverse effects include:
* **Gastrointestinal:** Bleeding, ulceration, perforation.
* **Cardiovascular:** Myocardial infarction, stroke, hypertension, edema.
* **Renal:** Renal papillary necrosis, interstitial nephritis, renal failure.
* **Hepatic:** Hepatotoxicity, elevated liver enzymes.
* **Hematologic:** Anemia, leukopenia, thrombocytopenia.
* **Hypersensitivity:** Anaphylaxis, 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):** Increased risk of gastrointestinal bleeding.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased methotrexate levels and risk of toxicity.
* **Diuretics and Antihypertensives:** NSAIDs can reduce the efficacy of these drugs and increase the risk of renal toxicity.
* **Other NSAIDs (including aspirin):** Increased risk of adverse effects, particularly gastrointestinal.
## Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease or those taking concomitant nephrotoxic agents.
* **Hepatic function:** Periodic liver function tests may be warranted in long-term therapy.
* **Gastrointestinal symptoms:** Monitor for signs of bleeding or ulceration.
* **Blood pressure:** Monitor for potential increases.
* **Signs of fluid retention or edema.**
## Clinical Pearls
* Mefenamic acid is intended for short-term use only.
* To minimize gastrointestinal upset, administer with food or milk.
* The lowest effective dose for the shortest duration necessary should be used to reduce the risk of serious cardiovascular and gastrointestinal events.
* Discontinue immediately if signs of hypersensitivity, gastrointestinal bleeding, or serious adverse effects occur.
* Avoid concurrent use with other NSAIDs, including low-dose aspirin for cardioprotection, unless specifically indicated and with careful risk-benefit assessment.
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**Disclaimer:** This information is intended for clinical use and does not replace full prescribing information or professional judgment. Always consult the current official prescribing information and relevant guidelines before making any clinical decisions.
