Antiulcer drugs are a class of drugs, exclusive of the antibacterial agents, used to treat ulcers in the stomach and the upper part of the small intestine. Antiulcer includes antacids, H2 antagonists, proton pump inhibitors, and miscellaneous. Antacids include aluminium hydroxide, calcium carbonate, magaldrate, magnesium hydroxide, magnesium trisilicate, and sodium bicarbonate. H2 antagonists include cimetidine, famotidine, and ranitidine. Proton pump inhibitors include esomeprazole, lansoprazole, omeprazole, pantoprazole, and rabeprazole. Action, uses, dosages and side effects of all these drugs are also covered in this chapter.