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# Mefenamic Acid
## Overview
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) from the fenamate class. It works by inhibiting cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis.
## Primary Indications
* Mild to moderate pain, including menstrual pain (dysmenorrhea).
* Rheumatoid arthritis and osteoarthritis (though not typically a first-line agent).
## Adult Dosing
* **Pain:** 500 mg every 6 hours as needed.
* **Rheumatoid arthritis/Osteoarthritis:** 500 mg three times daily.
* **Maximum daily dose:** 1500 mg. Treatment duration should not exceed 7 days for pain.
## Pediatric Dosing
* **Pain and Dysmenorrhea:** 500 mg as the initial dose, followed by 250 mg every 6 hours as needed. Do not exceed 1500 mg daily.
* **Safety and efficacy in children under 14 years of age for indications other than short-term pain relief have not been established.**
## Dose Adjustments
* **Renal Impairment:** Use with caution. No specific dose adjustment is universally recommended, but a reduced dose may be considered given the potential for renal toxicity with NSAIDs.
* **Hepatic Impairment:** Use with caution. No specific dose adjustment is universally recommended, but a reduced dose may be considered.
## Contraindications
* Hypersensitivity to mefenamic acid, aspirin, or other NSAIDs.
* History of bronchospasm, asthma, rhinitis, or urticaria following aspirin or NSAID use.
* Perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
* Active gastrointestinal bleeding or ulceration.
* Inflammatory bowel disease (IBD) in the active stage.
* Severe renal or hepatic impairment.
* Third trimester of pregnancy.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, constipation, dyspepsia, flatulence.
* **Serious:**
* **Gastrointestinal:** GI bleeding, ulceration, perforation.
* **Cardiovascular:** Increased risk of myocardial infarction and stroke.
* **Renal:** Renal papillary necrosis, interstitial nephritis, renal failure.
* **Hepatic:** Hepatitis, jaundice.
* **Hematologic:** Anemia, leukopenia.
* **Dermatologic:** Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN).
* **Hypersensitivity:** Anaphylaxis, angioedema.
## Key Drug Interactions
* **Anticoagulants (e.g., warfarin):** Increased risk of bleeding.
* **Corticosteroids:** Increased risk of GI ulceration and bleeding.
* **Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of GI bleeding.
* **Lithium:** Increased lithium levels and toxicity.
* **Methotrexate:** Increased methotrexate toxicity.
* **Diuretics and Antihypertensives (e.g., ACE inhibitors, ARBs, beta-blockers):** Reduced antihypertensive effect, increased risk of renal dysfunction.
* **Other NSAIDs and Aspirin:** Increased risk of adverse effects, particularly GI bleeding.
## Monitoring
* **Renal function:** Especially in elderly patients or those with pre-existing renal disease.
* **Hepatic function:** Particularly with long-term use or in patients with liver disease.
* **Signs and symptoms of GI bleeding:** Stool guaiac, hematemesis, melena.
* **Blood pressure:** NSAIDs can cause hypertension.
* **Signs of cardiovascular events.**
## Clinical Pearls
* Mefenamic acid is generally indicated for short-term use due to its gastrointestinal and cardiovascular risks.
* It should be taken with food or milk to minimize gastrointestinal upset.
* Avoid concurrent use with other NSAIDs.
* Due to potential drowsiness, patients should exercise caution when operating machinery or driving.
**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant guidelines before making clinical decisions. Drug information can change rapidly.
