Notes: Lansoprazole sulfone is a phase I metabolite of lansoprazole (Item Nos. 13627 / 21967 / 18235).{18257} Lansoprazole is a proton pump inhibitor that inactivates the hydrogen/potassium-stimulated ATPase pumps in parietal cells, thus inhibiting gastric acid secretion and increasing intragastric pH.{18250} Lansoprazole is metabolized by the cytochrome P450 (CYP) isoform CYP3A4 to form lansoprazole sulfone.{18257}