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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the anthranilic acid derivative class. It has analgesic, anti-inflammatory, and antipyretic properties.
## Primary Indications
* Mild to moderate pain, including menstrual pain (dysmenorrhea) and pain associated with dental procedures or minor surgery.
* Symptomatic relief of rheumatoid arthritis and osteoarthritis (though generally not preferred for chronic use due to GI risks).
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Dysmenorrhea:** 500 mg every 6 hours as needed, starting at the onset of pain and continuing for up to 3 days.
* **Rheumatoid Arthritis/Osteoarthritis:** 500 mg three times daily.
* **Maximum dose:** 1500 mg per day. Do not exceed 7 days of use for self-medication without consulting a healthcare professional.
## Pediatric Dosing
Mefenamic acid is generally **not recommended** for children under 14 years of age due to lack of established efficacy and safety data, and potential for adverse effects. Limited data suggests potential use in specific inflammatory conditions at doses of 6.5 mg/kg/dose every 6 hours, but this requires careful medical supervision.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Severe renal impairment is a contraindication.
* **Hepatic Impairment:** Use with caution. Severe hepatic impairment is a contraindication.
## 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.
* Inflammatory bowel disease (active or history).
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Gastrointestinal:** Dyspepsia, nausea, vomiting, diarrhea, abdominal pain, constipation, GI bleeding, ulceration, perforation.
* **Central Nervous System:** Dizziness, headache, drowsiness.
* **Renal:** Renal insufficiency, acute kidney injury.
* **Hematologic:** Leukopenia, thrombocytopenia, eosinophilia.
* **Dermatologic:** Rash, pruritus.
* **Other:** Bronchospasm, fluid retention, edema.
## 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 GI toxicity and other adverse effects.
* **Diuretics and Antihypertensives:** May decrease efficacy and increase risk of renal toxicity.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of GI bleeding.
## Monitoring
* **GI symptoms:** Assess for signs of bleeding or ulceration.
* **Renal function:** Monitor BUN and creatinine, especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** Monitor liver enzymes, especially in patients with pre-existing liver disease.
* **Blood pressure:** Monitor for potential increases.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize GI upset.
* Due to its short half-life, it is typically dosed every 6 hours.
* Avoid concurrent use with other NSAIDs unless specifically indicated and with caution.
* It is generally not considered a first-line agent for chronic inflammatory conditions like arthritis due to its safety profile.
* The risk of serious cardiovascular thrombotic events, myocardial infarction, and stroke associated with NSAID use may increase with duration of use.
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*Disclaimer: This information is for educational purposes only and does not constitute medical advice. Always consult the most current prescribing information and a qualified healthcare professional for any medical decisions.*
