proton-pump inhibitor

A proton-pump inhibitor (PPI) shuts off the stomach's acid factory at the final step. Instead of mopping up acid that is already made, it jams the pump that pushes acid out of the cell, so very little acid is produced in the first place.

PPIs such as omeprazole, esomeprazole, lansoprazole and pantoprazole are prodrugs that accumulate in the acidic spaces of active gastric parietal cells, where they are converted to a reactive form that covalently binds and irreversibly disables the H+/K+-ATPase — the proton pump that secretes hydrogen ions into the stomach. Because the block is irreversible, acid suppression outlasts the drug in the blood, and full effect builds over a few days as more pumps are inhibited.

They are the most powerful acid suppressors and are first-line for reflux disease, healing peptic ulcers, and protecting the stomach during NSAID use. They are generally well tolerated, but long-term use has been linked to lower magnesium, reduced vitamin B12 and calcium absorption, possible higher risk of certain gut infections, and rebound acid hypersecretion on stopping. They also rely on stomach acidity for activation, so timing before meals matters.