These are drugs that block the action of HISTAMINE at the H2 receptor (which otherwise would stimulate the acid-producing cells of the stomach lining to become active). By reducing the production of acid by the stomach, these drugs – chiefly cimetidine, ranitidine, famotidine and nizatidine – are valuable in the treatment of peptic ulcers (healing when used in high dose, and preventing relapse when used as maintenance therapy in reduced dose), reflux oesophagitis (see OESOPHAGUS, DISEASES OF), and the ZOLLINGER-ELLISON SYNDROME. These drugs are part of a range of treatments available in various combinations, including PROTON PUMP INHIBITORS and antibiotics which eradicate HELICOBACTER PYLORI. (See also DUODENAL ULCER.)