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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the fenamate class. It possesses analgesic, anti-inflammatory, and antipyretic properties. Its exact mechanism of action is not fully understood but is believed to involve inhibition of cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Management of mild to moderate pain, including menstrual pain (dysmenorrhea).
* Symptomatic relief of rheumatoid arthritis and osteoarthritis (though other NSAIDs may be preferred).
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg. Treatment duration typically should not exceed 7 days.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain and continuing for the duration of the symptoms.
* **Rheumatoid Arthritis/Osteoarthritis:** Doses range from 250 mg to 500 mg three times daily. Maximum daily dose is 1500 mg.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to limited safety and efficacy data.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe renal impairment. Data on specific dose adjustments is limited.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe hepatic impairment. Data on specific dose adjustments is limited.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, 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 gastrointestinal perforation, ulceration, or bleeding.
* Severe renal impairment.
* Severe hepatic impairment.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include: nausea, vomiting, diarrhea, abdominal pain, constipation, dizziness, headache, and rash.
Serious adverse effects include: gastrointestinal bleeding, perforation, ulceration, cardiovascular thrombotic events (myocardial infarction, stroke), renal impairment, hepatic injury, hypersensitivity reactions, and exacerbation of asthma.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of bleeding.
* **Lithium:** Increased lithium levels and risk of toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Other NSAIDs and Aspirin:** Increased risk of adverse effects, particularly gastrointestinal bleeding.
* **Diuretics and Antihypertensives:** May reduce their efficacy and increase risk of renal damage.
## Monitoring
* Monitor for signs and symptoms of gastrointestinal bleeding (e.g., melena, hematemesis).
* Monitor renal and hepatic function, especially in patients with pre-existing impairment or those on long-term therapy.
* Monitor blood pressure, as NSAIDs can cause hypertension.
* Assess for signs of cardiovascular events.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Due to its potential for gastrointestinal toxicity, it is generally reserved for short-term use.
* It is essential to use the lowest effective dose for the shortest duration necessary.
* Patients should be advised to report any signs of bleeding, such as black tarry stools or vomiting blood.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for definitive patient care decisions.*
