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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) used for the short-term relief of mild to moderate pain. It is a weak acid and an inhibitor of cyclooxygenase (COX) enzymes, which are involved in prostaglandin synthesis.
## Primary Indications
* Pain, including menstrual pain (dysmenorrhea)
* Rheumatoid arthritis (adjunctive therapy)
* Osteoarthritis (adjunctive therapy)
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Rheumatoid arthritis/Osteoarthritis:** 500 mg three times daily.
* **Maximum dose:** 4000 mg per day. Dosing duration should generally not exceed 7 days for pain.
## Pediatric Dosing
* Generally not recommended for children under 14 years of age for pain.
* For juvenile rheumatoid arthritis: 50 mg/kg/day divided into 3 or 4 doses. Do not exceed adult maximum dose.
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustment is recommended, but monitor renal function closely.
* **Hepatic Impairment:** Use with caution. No specific dose adjustment is recommended, but monitor hepatic function closely.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of gastrointestinal bleeding or perforation related to prior NSAID use.
* Active peptic ulceration or history of recurrent peptic ulceration.
* Severe heart failure.
* Third trimester of pregnancy.
## Adverse Effects
Common adverse effects include:
* Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia.
* Central Nervous System: Dizziness, drowsiness, headache.
* Renal: Renal impairment, interstitial nephritis.
* Hematologic: Anemia.
* Dermatologic: Rash, pruritus.
Serious adverse effects include:
* Gastrointestinal bleeding, ulceration, and perforation.
* Cardiovascular thrombotic events.
* Hepatotoxicity.
* Hypersensitivity reactions.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of gastrointestinal bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs):** Increased risk of gastrointestinal bleeding.
* **ACE inhibitors, ARBs, Beta-blockers:** May decrease antihypertensive effect and increase risk of renal dysfunction.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased methotrexate toxicity.
## Monitoring
* Signs and symptoms of gastrointestinal bleeding.
* Renal function (BUN, creatinine).
* Hepatic function (LFTs).
* Blood pressure.
* Signs of hypersensitivity reactions.
## Clinical Pearls
* Administer with food or milk to minimize gastrointestinal upset.
* Limit use to the shortest duration necessary to control symptoms.
* Avoid concomitant use with other NSAIDs or aspirin.
* Consider gastroprotective agents (e.g., PPIs) in patients at high risk for GI complications.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before making clinical decisions.
