1. Clinical Overview
Rabeprazole is a second-generation proton pump inhibitor (PPI) that suppresses gastric acid secretion by inhibiting the H+/K+ ATPase enzyme system (proton pump) at the secretory surface of the gastric parietal cell. It is a substituted benzimidazole prodrug that is activated in the acidic environment of the parietal cell canaliculus. It provides rapid, potent, and long-lasting inhibition of gastric acid secretion, making it a cornerstone therapy for acid-related disorders in the Indian population.
| Onset | Duration | Bioavailability |
|---|---|---|
| Within 1 hour for acid suppression; maximal effect within 2-4 hours. | Acid suppression lasts for 24-48 hours after a single dose; full therapeutic effect for healing may take 1-4 weeks. | Approximately 52% (oral tablet). |
2. Mechanism of Action
Rabeprazole is a prodrug. In the highly acidic environment of the parietal cell canaliculus, it is converted to its active sulfenamide form. This active metabolite forms covalent disulfide bonds with cysteine residues (specifically Cys813 and Cys822) on the alpha subunit of the H+/K+ ATPase enzyme (the proton pump), irreversibly inhibiting its function. This prevents the final step of gastric acid secretion, the exchange of intracellular H+ for luminal K+.
3. Indications & Uses
- Gastroesophageal Reflux Disease (GERD) - Healing of erosive esophagitis & maintenance of healing
- Duodenal Ulcer - Healing & maintenance
- Gastric Ulcer - Healing
- Pathological Hypersecretory Conditions (e.g., Zollinger-Ellison Syndrome)
- Eradication of Helicobacter pylori (in combination with antibiotics like amoxicillin and clarithromycin)
4. Dosage & Administration
Adult Dosage: GERD/Erosive Esophagitis: 20mg once daily for 4-8 weeks. Maintenance: 10-20mg once daily. Duodenal/Gastric Ulcer: 20mg once daily for 4-6 weeks. H. pylori Eradication: 20mg twice daily for 7-14 days as part of combination therapy. Hypersecretory Conditions: 60mg once daily, titrated up to 100mg/day or 60mg twice daily.
Administration: Swallow the tablet whole with a glass of water; do not crush, split, or chew. Should be taken in the morning, before a meal (preferably breakfast), for optimal acid control. For twice-daily dosing, take before morning and evening meals. Delayed-release tablets are designed to protect the drug from stomach acid.
5. Side Effects
Common side effects may include:
- Headache
- Nausea
- Diarrhea
- Abdominal pain
- Flatulence
- Constipation
- Dry mouth
- Dizziness
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Ketoconazole, Itraconazole | Decreased absorption of these azole antifungals due to increased gastric pH. | Major |
| Atazanavir, Rilpivirine | Significantly decreased plasma concentration and loss of efficacy of these HIV protease/NNRTI inhibitors. | Contraindicated/Major |
| Warfarin | Potential increased INR and risk of bleeding due to possible interaction (monitor INR closely). | Moderate |
| Methotrexate | May decrease renal clearance of methotrexate, increasing toxicity risk. | Moderate |
| Digoxin | Increased bioavailability of digoxin due to higher gastric pH. | Moderate |
| Iron Salts (Ferrous sulfate), Dabigatran | Decreased absorption, potentially reducing efficacy. | Moderate |
| Clopidogrel | Theoretical concern due to CYP2C19 inhibition, but Rabeprazole has the weakest interaction among PPIs. Clinical significance is debated. | Minor/Moderate |
7. Patient Counselling
- DO take the tablet whole, with water, before a meal (usually breakfast).
- DO complete the full course as prescribed, even if symptoms improve.
- DO inform your doctor if you are taking any other medicines, especially blood thinners, antifungals, or HIV medications.
- DON'T crush, chew, or split the tablet.
- DON'T take it with high-fat meals just before dosing, as it may delay absorption.
- DON'T use for immediate relief of heartburn; it takes 1-3 days for full effect.
8. Toxicology & Storage
Overdose: Experience is limited. Expected symptoms would be an extension of the pharmacologic effect (profound acid suppression) and may include drowsiness, blurred vision, tachycardia, nausea, vomiting, diaphoresis, flushing, headache, dry mouth, and confusion.
Storage: Store below 30°C, in a cool, dry place. Protect from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.