Cimetidine, sold as Tagamet, is a compound related to histamine. It is a H2 antagonist drug, also called H2RAs or H2 blockers, and was the first of this class to be discovered. H2 antagonist drugs compete with histamine to bind to the histamine H2-receptors found on the basolateral membrane of gastric parietal cells. This blocks histamine effects, resulting in reduced gastric acid secretion and a reduction in gastric volume and acidity. Cimetidine also helps to block pepsin and gastrin output, and due to the inhibition of gastric acid secretion, it is typically used to treat heartburn and ulcers. Cimetidine also blocks the activity of cytochrome P-450 enzymes CYP1A2, 2C9, 2C19, 2D6, 2E1 and 3A4, which may affect the metabolism of other drugs.

Cimetidine Pathway References