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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) of the fenamate class. It functions by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Short-term management of mild to moderate pain, including menstrual pain (dysmenorrhea).
* Relief of symptoms associated with rheumatoid arthritis and osteoarthritis.
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed. Maximum daily dose is 1500 mg. Dosing should not exceed 7 days.
* **Dysmenorrhea:** 500 mg every 4-6 hours as needed, starting at the onset of pain. Maximum daily dose is 1500 mg. Dosing should not exceed 7 days.
* **Rheumatoid Arthritis/Osteoarthritis:** 500 mg three times daily, with food. Duration of therapy depends on clinical response.
## Pediatric Dosing
Mefenamic acid is generally not recommended for children under 14 years of age due to limited efficacy and safety data.
## 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.
* Peri-operative 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), dyspepsia, headache, dizziness, and rash. Serious risks include gastrointestinal bleeding, ulceration, perforation, cardiovascular thrombotic events, renal toxicity, and hypersensitivity 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) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of bleeding.
* **Lithium:** Increased serum lithium levels, leading to toxicity.
* **Methotrexate:** Increased methotrexate toxicity.
* **Diuretics and Antihypertensives (e.g., ACE inhibitors, ARBs, beta-blockers):** Reduced efficacy and increased risk of renal impairment.
## Monitoring
* **Gastrointestinal Symptoms:** Monitor for signs and symptoms of bleeding or ulceration.
* **Renal Function:** Monitor serum creatinine and BUN, especially in patients with pre-existing renal disease or those receiving concomitant nephrotoxic agents.
* **Hepatic Function:** Monitor liver enzymes, especially with prolonged use.
* **Blood Pressure:** Monitor blood pressure, as NSAIDs can increase it.
* **Signs of Cardiovascular Events:** Patients should be aware of and report any signs of myocardial infarction or stroke.
## Clinical Pearls
* Administer with food or milk to minimize gastrointestinal upset.
* Use the lowest effective dose for the shortest duration necessary.
* Avoid concomitant use with other NSAIDs.
* Discontinue if any signs of hypersensitivity, severe gastrointestinal issues, or cardiovascular events occur.
* Not a first-line agent for chronic pain due to risks associated with long-term NSAID use.
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**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 your healthcare provider for any questions regarding drug therapy.
