Ulcerex (Ranitidine) is a potent long acting histamine H2 receptor antagonist for the treatment of duodenal and gastric ulcer. It inhibits basal and stimulated secretion of gastric acid, reducing both the volume & the acid and pepsin content of the secretion. Ranitidine has relatively larger duration of action & so a single 150 mg dose effectively suppresses gastric acid secretion for 12 hours.