SCH 28080 is a reversible K+-competitive inhibitor of H+/K+-ATPases that is best known for its ability to block acid secretion through its action against the gastric H+/K+-ATPase (IC50 = 1.3 μM). It is effective against gastric H+/K+-ATPases from a variety of species and can inhibit colonic H+/K+-ATPases, but this activity appears to be species-dependent. SCH 28080 is also used to investigate the role of H+/K+-ATPases in non-mammalian organisms and to distinguish the actions of H+/K+-ATPases from other ATP-dependent transporters.