Nolinium bromide (NB) is a nonanticholinergic, gastric acid antisecretory agent and a gastrointestinal tract antispasmodic agent. The gastrointestinal antispasmodic action of NB has been demonstrated in a variety of test systems. The compound inhibited electrically induced contractions of rabbit ileum and nicotine-induced contractions of rat ileum in vitro, gastric emptying in fasted rats, and intestinal transport of a charcoal meal in mice. In the anesthetized dog, NB antagonized colonic contractions induced by acetylcholine, histamine, serotonin, and pelvic nerve stimulation, and duodenal contractions due to vagal stimulation and acetylcholine. In the unanesthetized dog, feeding induced colonic and duodenal motilities were inhibited by NB. The antisecretory action of NB may involve inhibition of enzymes of gastric acid secretion, specifically histamine-stimulated adenylate cyclase and potassium-stimulated ATPase. NB has no direct histamine-H2 receptor blocking properties. Nolinium bromide inhibits in a dose-dependent manner both the gastric H+, K+-ATPase activity and H+ uptake ability of the gastric microsomes. Increasing concentrations of K+ could reverse the nolinium bromide inhibition of both the H+, K+-ATPase activity and vesicular H+ transport. Nolinium bromide interferes primarily with the K+-dependent phosphatase step and thereby reduces the turnover of the enzyme. The drug acts as a K+ antagonist in the gastric H+ +K+-dependent ATPase reaction.