Source:http://linkedlifedata.com/resource/umls/id/C0019593
MSH: Drugs that selectively bind to but do not activate histamine H2 receptors, thereby blocking the actions of histamine. Their clinically most important action is the inhibition of acid secretion in the treatment of gastrointestinal ulcers. Smooth muscle may also be affected. Some drugs in this class have strong effects in the central nervous system, but these actions are not well understood.,NCI: Any agent that competitively binds to and blocks the histamine H2 receptors found in the stomach, heart, uterus, on vascular smooth muscle and in the central nervous system (CNS). Of particular clinical relevance is the blockage of H2 receptors found on the parietal cells of the stomach, which prevents gastric acid secretion.