Tiotidine is a controversial histamine H2 receptor ligand with negligible activity against H1- and H3- receptors. It was found that tiotidine behaves as an inverse agonist in U-937 cells, diminishing basal cAMP levels. Tiotidine showed two binding sites, one with high affinity and low capacity and the other with low affinity and high capacity. Tiotidine is currently in use as a radioligand in histamine H2-receptor binding studies. Compared to cimetidine, tiotidine appears to be approximately eight times more potent on a molar basis than cimetidine as an inhibitor of acid secretion, and the tiotidine effect is more prolonged. It was developed for the treatment of peptic ulcer.