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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 and for the treatment of primary dysmenorrhea. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Mild to moderate pain (e.g., dental pain, post-operative pain)
* Primary dysmenorrhea
## Adult Dosing
* **Pain:** 500 mg orally every 6 hours as needed. Do not exceed 1500 mg in 24 hours.
* **Primary Dysmenorrhea:** 500 mg orally every 6 hours, starting at the onset of pain or bleeding and continuing for the duration of symptoms, up to 3 days.
## Pediatric Dosing
Mefenamic acid is generally **not recommended for use in pediatric patients under 14 years of age** due to lack of established efficacy and safety data. However, some sources suggest potential use in older adolescents (14 years and older) with the same dosing as adults.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose adjustments are not well-defined, but reduced doses may be considered in severe impairment.
* **Hepatic Impairment:** Use with caution. Monitor liver function closely. Dose adjustments are not well-defined.
## 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.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include gastrointestinal upset (nausea, vomiting, diarrhea, abdominal pain), dizziness, drowsiness, and headache. Serious adverse effects can include:
* **Gastrointestinal:** Ulceration, bleeding, perforation.
* **Cardiovascular:** Increased risk of myocardial infarction, stroke, and heart failure.
* **Renal:** Renal impairment or failure.
* **Hepatic:** Hepatotoxicity.
* **Hematologic:** Anemia.
* **Dermatologic:** Severe skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis).
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **SSRIs/SNRIs:** Increased risk of GI bleeding.
* **Other NSAIDs/Salicylates:** Increased risk of adverse effects.
* **Lithium:** Increased lithium levels.
* **Methotrexate:** Increased methotrexate toxicity.
* **Diuretics and Antihypertensives:** May reduce efficacy and increase risk of renal toxicity.
## Monitoring
* **GI Bleeding:** Monitor for signs and symptoms (e.g., melena, hematemesis).
* **Renal Function:** Monitor BUN and creatinine, especially in patients with pre-existing renal disease or those on concomitant nephrotoxic agents.
* **Hepatic Function:** Monitor LFTs, especially in patients with liver disease or those on long-term therapy.
* **Blood Pressure:** Monitor blood pressure, as NSAIDs can cause hypertension.
* **Signs of Cardiovascular Events:** Educate patients on symptoms and advise prompt medical attention.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Due to its potential for GI toxicity and cardiovascular risks, mefenamic acid should be used for the shortest duration necessary.
* It is generally not recommended for long-term use.
* Be aware of the potential for pseudo-allergy in patients with aspirin sensitivity.
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*This information is intended for healthcare professionals and does not replace current prescribing information or professional medical advice. Always verify with the most up-to-date drug information and consider individual patient factors.*
