Which drug acts as an H2-receptor antagonist in the treatment of Zollinger-Ellison syndrome?

Cimetidine is classified as an H2-receptor antagonist, which specifically targets the histamine H2 receptors in the stomach lining. By blocking these receptors, cimetidine effectively reduces the secretion of gastric acid, making it useful in treating conditions characterized by excessive acid production, such as Zollinger-Ellison syndrome.

In Zollinger-Ellison syndrome, gastrin-secreting tumors cause an overproduction of gastric acid, leading to severe ulcers and related gastrointestinal symptoms. By inhibiting the action of histamine on the H2 receptors, cimetidine helps to lower acid secretion and manage the symptoms associated with this syndrome.

While other options like omeprazole are also involved in reducing gastric acid, they function via a different mechanism by inhibiting the proton pump in the stomach rather than targeting H2 receptors directly. Atropine, on the other hand, is an anticholinergic medication that reduces gastric secretions but isn't an H2-receptor antagonist. Ranitidine is another H2-receptor antagonist similar to cimetidine, but cimetidine is the more classically recognized drug for this specific query regarding Zollinger-Ellison syndrome.