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# Mefenamic acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term treatment of mild to moderate pain. It works by inhibiting prostaglandin synthesis.
## Primary Indications
* Pain, including menstrual pain (dysmenorrhea) and pain associated with osteoarthritis and rheumatoid arthritis.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Do not exceed 1500 mg in the first 24 hours of treatment, and do not exceed 1000 mg for any single dose. Treatment should not exceed 7 days.
* **Dysmenorrhea:** 500 mg every 6 hours, started at the onset of menstrual pain and any associated symptoms. Treatment should not exceed 7 days.
## Pediatric Dosing
* Mefenamic acid is generally not recommended for children under 14 years of age due to limited data and potential risks. If used, dosing may be based on weight, but specific recommendations are scarce and often depend on institutional guidelines or expert consultation.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Dose reduction may be necessary in severe renal impairment.
* **Hepatic Impairment:** Use with caution. Dose reduction may be necessary in severe hepatic 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.
* Inflammatory bowel disease.
* Severe heart failure, renal impairment, or hepatic impairment.
## Adverse Effects
Common adverse effects include: diarrhea, nausea, vomiting, abdominal pain, constipation, dizziness, rash, and headache. Serious adverse effects may include: gastrointestinal bleeding, ulceration, perforation, cardiovascular thrombotic events, myocardial infarction, stroke, renal failure, and hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of bleeding.
* **Other NSAIDs and Aspirin:** Increased risk of adverse effects, particularly gastrointestinal bleeding.
* **Diuretics and Antihypertensives:** May reduce antihypertensive effect and increase risk of renal impairment.
* **Lithium:** Increased serum lithium levels.
* **Methotrexate:** Increased methotrexate toxicity.
## Monitoring
* **Renal function:** Monitor especially in patients with pre-existing renal disease or those at risk.
* **Hepatic function:** Monitor especially in patients with pre-existing hepatic disease.
* **Gastrointestinal symptoms:** Assess for signs and symptoms of bleeding or ulceration.
* **Blood pressure:** Monitor for potential increases.
## Clinical Pearls
* Mefenamic acid is intended for short-term use only (maximum 7 days).
* It should be taken with food or milk to minimize gastrointestinal upset.
* Due to its short half-life, it is dosed every 6 hours.
* Consider the risks of NSAIDs, including cardiovascular and gastrointestinal events, especially with prolonged use or in high-risk patients.
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**Disclaimer:** This information is intended for clinical pharmacy use and does not replace the most current prescribing information. Always consult the official product monograph or a reliable drug information resource for complete and up-to-date details before prescribing or dispensing.
