Ranitidine

# Ranitidine ## Overview - **Classification**: H2-receptor antagonist - **Mechanism**: Competitively inhibits histamine at H2-receptors on gastric parietal cells, reducing gastric acid secretion. ## Primary Indications 1. **Duodenal/Gastric Ulcers**: Treatment and maintenance. 2. **Gastroesophageal Reflux Disease (GERD)/Erosive Esophagitis**: Symptom relief and healing. 3. **Pathological Hypersecretory Conditions**: E.g., Zollinger-Ellison Syndrome. 4. **Stress Ulcer Prophylaxis**: In critically ill patients. ## Adult Dosing ### Standard Dosing **Active Duodenal/Gastric Ulcers** - **Dose**: **150 mg** - **Frequency**: Twice daily (BID) or **300 mg** once daily (QHS) - **Route**: Oral (PO) - **Duration**: 4-8 weeks **Duodenal Ulcer (Maintenance)** - **Dose**: **150 mg** - **Frequency**: Once daily (QHS) - **Route**: Oral (PO) **GERD/Erosive Esophagitis** - **Dose**: **150 mg** - **Frequency**: Twice daily (BID) - **Route**: Oral (PO) - **Duration**: Up to 6 weeks for GERD, up to 12 weeks for erosive esophagitis. - **Max Dose**: Up to **300 mg** BID for severe cases. **Pathological Hypersecretory Conditions (e.g., Zollinger-Ellison Syndrome)** - **Dose**: **150 mg** - **Frequency**: Three times daily (TID) initially - **Route**: Oral (PO) - **Maximum Dose**: Up to **6 g/day** in divided doses. ### Dose Adjustments - **Renal Impairment**: - CrCl < 50 mL/min: **150 mg** every 24 hours (for most indications). - Or **50 mg** IV every 18-24 hours. - Administer dose after hemodialysis. - **Hepatic Impairment**: Use with caution. No specific dose adjustment generally required, but monitor. - **Elderly Patients**: No specific dose adjustment, but assess renal function. ## Pediatric Dosing ### Neonates (0-28 days) - **Indication**: GERD - **Dose**: **2 mg/kg** - **Frequency**: Every 8-12 hours (q8-12h) - **Maximum**: **4 mg/kg/day** - **Special Notes**: Limited data; use with caution. Oral solution preferred. ### Infants (1-12 months) - **Indication**: GERD, Ulcer Treatment - **Dose**: **2-4 mg/kg** - **Frequency**: Twice daily (BID) - **Maximum**: **100 mg** per dose (oral) - **Special Notes**: Oral solution or crushed tablet in liquid. ### Children (1-12 years) - **Indication**: GERD, Ulcer Treatment - **Dose**: **2-4 mg/kg** - **Frequency**: Twice daily (BID) - **Maximum**: **150 mg** per dose (oral) or **300 mg/day** (oral) ### Adolescents (13-18 years) - **Indication**: GERD, Ulcer Treatment - **Dose**: Adult dosing typically applies. - **Maximum**: **300 mg/day** for maintenance, up to **6 g/day** for Zollinger-Ellison. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to ranitidine or other H2-receptor antagonists. - **Absolute**: Acute porphyria (can precipitate attacks). ### Common Adverse Effects - **Common (1-10%)**: Headache, nausea, vomiting, diarrhea, constipation. - **Common (1-10%)**: Dizziness, fatigue. - **Serious but Rare**: Bradycardia, tachycardia, arrhythmias (IV use), hepatotoxicity, blood dyscrasias, Stevens-Johnson syndrome. ### Key Drug Interactions - **Antacids**: Decrease ranitidine absorption; separate administration by >1 hour. - **Drugs requiring acidic environment (e.g., ketoconazole, atazanavir)**: Ranitidine reduces absorption; avoid concomitant use or monitor closely. - **Warfarin**: Potential for increased INR; monitor PT/INR closely. - **Theophylline**: Increased theophylline levels possible at high ranitidine doses; monitor levels. ## Monitoring & Follow-up - **Before Treatment**: Assess renal function (CrCl). - **During Treatment**: Monitor for symptom improvement. - **During Treatment**: For long-term or high-dose, monitor liver enzymes, CBC. - **Clinical Signs**: Watch for GI bleeding, signs of CNS effects (elderly), hepatotoxicity. ## Clinical Pearls - 💡 **Tip 1**: Due to probable human carcinogen (NDMA) concerns, ranitidine products have been largely **withdrawn from global markets**. Famotidine is a common alternative. - 💡 **Tip 2**: Administer ranitidine with or without food. - 💡 **Tip 3**: Avoid in patients with a history of acute porphyria due to risk of exacerbation. - 💡 **Tip 4**: For IV administration, dilute appropriately and infuse over 15-20 minutes to avoid bradycardia. - 💡 **Tip 5**: OTC ranitidine doses are lower; counsel patients on appropriate use if still available in certain regions. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.