proton-pump inhibitor proton-pump inhibitor proton-pump inhibitors (ppis) are a class of medications that cause a profound and prolonged reduction of stomach acid production. they do so by irreversibly inhibiting the stomach's h+/k+ atpase proton pump. proton-pump inhibitordrug classgeneral structure of a proton-pump inhibitorclass identifiersusereduction of gastric acid productionatc codea02bcmechanism of actionenzyme inhibitorbiological targeth+/k+ atpaseclinical datadrugs.comdrug classeswebmdmedicinenet