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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It is thought to exert its analgesic and anti-inflammatory effects by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain.
* Management of primary dysmenorrhea.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg. Treatment should not exceed 7 days.
* **Dysmenorrhea:** 500 mg every 6 hours starting at the onset of pain and bleeding, and continuing for the duration of dysmenorrhea. Treatment should not exceed 7 days.
## Pediatric Dosing
Mefenamic acid is generally not recommended for use in children younger than 14 years for pain relief due to lack of established safety and efficacy. Some sources suggest use for dysmenorrhea in adolescents 12 years and older at adult doses, but caution is advised.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Data is limited, but dose reduction may be considered in severe impairment.
* **Hepatic Impairment:** Use with caution. Data is limited, but dose reduction may be considered in severe impairment.
## Contraindications
* Known 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.
## Adverse Effects
Common adverse effects include nausea, vomiting, diarrhea, abdominal pain, constipation, dizziness, and headache. Serious adverse effects include gastrointestinal bleeding, ulceration, perforation, cardiovascular thrombotic events, renal toxicity, hepatic toxicity, and severe skin reactions.
## 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 bleeding.
* **ACE inhibitors, Angiotensin II Receptor Blockers (ARBs):** May increase risk of renal impairment and reduce antihypertensive efficacy.
* **Diuretics:** May increase risk of renal impairment and reduce diuretic efficacy.
* **Lithium:** Increased serum lithium levels, potentially leading to toxicity.
* **Methotrexate:** Increased risk of methotrexate toxicity.
## Monitoring
* **Gastrointestinal:** Monitor for signs and symptoms of bleeding (e.g., melena, hematemesis).
* **Cardiovascular:** Assess for signs of potential cardiovascular events.
* **Renal Function:** Monitor renal function, especially in patients with pre-existing renal disease.
* **Hepatic Function:** Monitor liver function tests, especially in patients with hepatic impairment.
## Clinical Pearls
* Mefenamic acid should be taken with food or milk to minimize gastrointestinal upset.
* Due to its potential for serious adverse effects, mefenamic acid should be used at the lowest effective dose for the shortest duration necessary.
* Consideration should be given to the risks versus benefits, especially in elderly patients or those with risk factors for cardiovascular or gastrointestinal events.
* The risk of cardiovascular thrombotic events may increase with duration of use.
**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions.
