Lansoprazole is used to reduce gastric acid secretion, short term treatment of active gastric ulcers, active duodenal ulcers, erosive reflux oesophagitis, symptomatic gastroesophageal reflux disease, and non-steroidal anti-inflammatory drug (NSAID) induced gastric and duodenal ulcers. It is also useful in the management of hypersecretory conditions including Zollinger-Ellison syndrome. Lansoprazole is effective at eradicating H. pylori when used in conjunction with amoxicillin and clarithromycin (triple therapy) or with amoxicillin alone (dual therapy).. Lansoprazole is a prodrug administered orally but since it degrades rapidly at low pH, the capsule contains enteric-coated granules. After undergoing absorption in the small intestine, it passes from the blood stream into the parietal cells in the stomach, then enters the stomach lumen. It is a weak base and thus, accumulates on the outside of cell in the acidic environment. Its main target is the H+/K+ ATPase in the parietal cells in the stomach. In parietal cells, carbonic anhydrase converts water and carbon dioxide to hydrogen bicarbonate ions and H+. The bicarbonate ions go into the blood via the chloride anion exchanger on the basolateral membrane which exchanges the hydrogen bicarbonate for Cl- ions. There is also the Na+/K+ ATPase which pumps Na+ out of the cell and K+ into the cell. The H+/K+ ATPase is located on the apical membrane and pumps the H+ from the cell into the stomach lumen and K+ from the lumen into the cell. Another transporter, the K+/Cl- symporter transports K+ and Cl- in the stomach lumen. The H+ and Cl- in the stomach lumen forms the HCl acid which, in excess, can cause disorders like ulcers. The acidic environment in the stomach converts the prodrug lansoprazole into its active form, sulfenamide. Sulfenamide then covalently binds to the cysteine residues on the alpha subunit of the H+/K+ ATPase via disulfide bridges. This binding of sulfenamide irreversibly inhibits the H+/K+ ATPase, preventing too much acid secretion in the stomach. Less acid in the stomach is favorable for symptomatic relief of disorders caused by the acid. Side effects of taking lansoprazole may include headache, diarrhea, vomiting, stomach pain, constipation, skin rashes, dizziness, fatigue, dry mouth.

Lansoprazole Pathway References