1. Clinical Overview
Lansoprazole is a proton pump inhibitor (PPI) that suppresses gastric acid secretion by specific inhibition of the H+/K+ ATPase enzyme system 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 is widely used in the management of acid-peptic disorders and is available in India as capsules, orally disintegrating tablets (ODTs), and sachets.
| Onset | Duration | Bioavailability |
|---|---|---|
| Within 1-2 hours after oral administration. | The antisecretory effect persists for more than 24 hours. Full therapeutic effect for healing of erosive esophagitis may take up to 4-8 weeks. | Approximately 80-85% after oral administration. Bioavailability may be decreased if taken with food. |
2. Mechanism of Action
Lansoprazole is a prodrug. In the acidic environment of the parietal cell canaliculus (pH < 4), it is converted to its active form, sulfenamide. This active metabolite forms covalent disulfide bonds with cysteine residues (specifically Cys813 and Cys321) on the extracellular domain of the H+/K+ ATPase (proton pump), irreversibly inhibiting the enzyme's function.
3. Indications & Uses
- Healing of Erosive Reflux Esophagitis (GERD)
- Maintenance of Healed Erosive Esophagitis
- Healing of Duodenal Ulcers
- Healing of Gastric Ulcers
- Eradication of Helicobacter pylori (in combination with antibiotics)
4. Dosage & Administration
Adult Dosage: Erosive Esophagitis: 30mg once daily for 4-8 weeks. Maintenance: 15mg once daily. Duodenal/Gastric Ulcer: 30mg once daily for 4-8 weeks. H. pylori Eradication: 30mg twice daily + amoxicillin 1g twice daily + clarithromycin 500mg twice daily for 10-14 days (or other regimen as per local guidelines). Hypersecretory Conditions: Starting dose 60mg once daily, adjust individually (max 120mg/day in divided doses).
Administration: Take on an empty stomach, at least 30-60 minutes before the first meal of the day (typically breakfast). Swallow capsule whole; do not crush, chew, or split. For patients with swallowing difficulties: Capsule can be opened and granules sprinkled on 1 tablespoon of applesauce, yogurt, or acidic fruit juice (e.g., apple, orange) and swallowed immediately without chewing. ODT: Place on tongue, allow to disintegrate with or without water, and swallow. Do not split ODT.
5. Side Effects
Common side effects may include:
- Headache
- Diarrhea
- Nausea
- Abdominal pain
- Constipation
- Flatulence
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Atazanavir, Rilpivirine | Decreased absorption and plasma concentration of these HIV drugs due to increased gastric pH, leading to loss of virologic response. | Major - Contraindicated. |
| Clopidogrel | Lansoprazole (a moderate CYP2C19 inhibitor) may reduce the antiplatelet effect of clopidogrel (a prodrug activated by CYP2C19), potentially increasing cardiovascular risk. Consider pantoprazole or H2 blockers. | Moderate |
| Methotrexate | May decrease renal clearance of methotrexate, potentially increasing toxicity. Monitor closely with high-dose methotrexate. | Moderate |
| Warfarin | Potential for increased INR and risk of bleeding due to possible interaction. Monitor INR closely when starting or stopping lansoprazole. | Moderate |
| Ketoconazole, Itraconazole, Erlotinib | Decreased absorption of these drugs due to increased gastric pH, reducing their efficacy. | Moderate |
| Tacrolimus | May increase tacrolimus blood levels. Monitor tacrolimus concentrations. | Moderate |
| Digoxin | Increased bioavailability of digoxin due to elevated gastric pH. Monitor digoxin levels. | Minor |
7. Patient Counselling
- DO take the medication on an empty stomach, 30-60 minutes before breakfast.
- DO swallow the capsule whole with a glass of water. Do not crush or chew.
- DO inform your doctor if you are pregnant, planning pregnancy, or breastfeeding.
- DO inform your doctor about all other medications, vitamins, and herbal supplements you are taking.
- DONT take the medication with food as it reduces effectiveness.
- DONT open the capsule and mix with liquids other than those recommended (e.g., applesauce). Do not mix with milk, water, or carbonated drinks in the sprinkle method.
- DONT stop taking the medication abruptly if used long-term; consult your doctor for a tapering plan to avoid rebound acidity.
8. Toxicology & Storage
Overdose: Overdose experience is limited. Expected symptoms would be an extension of the pharmacologic effect: hypochlorhydria, and possibly the known adverse effects like confusion, drowsiness, blurred vision, tachycardia, nausea, diaphoresis, flushing, headache, and dry mouth.
Storage: Store below 30°C, in a cool, dry place. Protect from moisture and light. Keep out of reach of children. Do not use after the expiry date printed on the pack. For ODTs: Keep in the original blister pack until use to protect from moisture.