Mefenamic

# Mefenamic ## Overview - **Classification**: Nonsteroidal Anti-inflammatory Drug (NSAID), Anthranilic acid derivative - **Mechanism**: Inhibits cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) enzymes, leading to decreased prostaglandin synthesis. This reduces inflammation, pain, and fever. ## Primary Indications 1. **Dysmenorrhea**: Treatment of primary dysmenorrhea (menstrual pain). 2. **Mild to Moderate Pain**: Short-term relief of mild to moderate pain. ## Adult Dosing ### Standard Dosing **Primary Dysmenorrhea** - **Dose**: **500 mg** - **Frequency**: Once, then **250 mg** every 6 hours - **Route**: Oral - **Duration**: Typically 2-3 days, not exceeding 7 days. **Mild to Moderate Pain** - **Dose**: **500 mg** - **Frequency**: Once, then **250 mg** every 6 hours - **Route**: Oral - **Duration**: Not exceeding 7 days. ### Dose Adjustments - **Renal Impairment**: **Contraindicated** in severe renal impairment (CrCl <30 mL/min) due to risk of renal toxicity. Use with extreme caution in moderate impairment. - **Hepatic Impairment**: **Contraindicated** in severe hepatic impairment due to risk of worsening liver function. Use with caution in mild to moderate impairment. - **Elderly Patients**: Use lowest effective dose for shortest duration. Increased risk of GI, renal, and cardiovascular adverse effects. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: **Not recommended**. - **Special Notes**: Safety and efficacy not established. Risk of severe adverse effects. ### Infants (1-12 months) - **Dose**: **Not recommended**. - **Special Notes**: Safety and efficacy not established. ### Children (1-12 years) - **Dose**: **Not recommended**. - **Special Notes**: Safety and efficacy not established for general use. In some regions, *occasionally* used cautiously in children >6 months for specific indications, but general US guidance is **not before 14 years**. ### Adolescents (13-18 years) - **Dose**: Apply **adult dosing** recommendations for patients **14 years and older**. - **Frequency**: **500 mg** once, then **250 mg** every 6 hours. - **Maximum**: **1250 mg/day**. - **Special Notes**: Short-term use only, not exceeding 7 days. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to mefenamic acid or other NSAIDs. - **Absolute**: History of asthma, urticaria, or allergic-type reactions after aspirin or other NSAIDs. - **Absolute**: Active gastrointestinal bleeding or peptic ulcer disease. - **Absolute**: Severe renal impairment (CrCl <30 mL/min). - **Absolute**: Severe heart failure. - **Absolute**: Coronary Artery Bypass Graft (CABG) surgery (peri-operative pain). - **Absolute**: Pregnancy (third trimester). ### Common Adverse Effects - **Common (1-10%)**: Diarrhea, nausea, vomiting, abdominal pain, dyspepsia. - **Common (1-10%)**: Headache, dizziness, drowsiness. - **Common (1-10%)**: Rash. - **Serious but Rare**: Gastrointestinal bleeding, ulceration, perforation. - **Serious but Rare**: Acute kidney injury, renal papillary necrosis. - **Serious but Rare**: Cardiovascular thrombotic events (MI, stroke). - **Serious but Rare**: Severe skin reactions (SJS, TEN). - **Serious but Rare**: Hematologic effects (anemia, leukopenia, thrombocytopenia). ### Key Drug Interactions - **Anticoagulants (e.g., Warfarin)**: Increased risk of bleeding. **Monitor INR closely**. - **Antiplatelets (e.g., Aspirin, Clopidogrel)**: Increased risk of bleeding. - **SSRIs**: Increased risk of GI bleeding. - **Diuretics (e.g., Furosemide, Thiazides)**: Reduced diuretic and antihypertensive effects; increased risk of renal impairment. - **ACE Inhibitors/ARBs**: Reduced antihypertensive effects; increased risk of renal impairment. - **Lithium**: Increased lithium plasma levels, leading to toxicity. **Monitor lithium levels**. - **Methotrexate**: Increased methotrexate levels, leading to toxicity. **Avoid concomitant use if possible**. ## Monitoring & Follow-up - **Before Treatment**: Assess GI risk factors, renal function (CrCl), hepatic function. - **During Treatment**: Monitor for signs of GI bleeding (black stools, vomiting blood). - **During Treatment**: Monitor for fluid retention, edema, increased blood pressure. - **Clinical Signs**: Watch for unusual bruising/bleeding, severe abdominal pain, persistent diarrhea, changes in urine output. ## Clinical Pearls - 💡 **Tip 1**: Mefenamic acid is known for causing diarrhea; advise patients. - 💡 **Tip 2**: Always take with food or milk to minimize GI upset. - 💡 **Tip 3**: Emphasize short-term use (typically 2-3 days for dysmenorrhea, max 7 days for pain). - 💡 **Tip 4**: Not recommended for long-term chronic pain management due to safety profile. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.