This invention relates to compounds of the formula (I): ##STR00001## or a pharmaceutically acceptable salt thereof, wherein: A, B, X, R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are each as described herein or a pharmaceutically acceptable salt, and compositions containing such compounds and the use of such compounds in the treatment of a condition mediated by acid pump antagonistic activity such as, but not limited to, as gastrointestinal disease, gastroesophageal disease, gastroesophageal reflux disease (GERD), peptic ulcer, gastric ulcer, duodenal ulcer, NSAID-induced ulcers, gastritis, infection of Helicobacter pylori, dyspepsia, functional dyspepsia, Zollinger-Ellison syndrome, non-erosive reflux disease (NERD), visceral pain, heartburn, nausea, esophagitis, dysphagia, hypersalivation, airway disorders or asthma.