<P> Antacids are distinct from acid - reducing drugs like H - receptor antagonists or proton pump inhibitors and they do not kill the bacteria Helicobacter pylori, which causes most ulcers . </P> <P> Versions with magnesium may cause diarrhea, and brands with calcium or aluminium may cause constipation and rarely, long - term use may cause kidney stones . Long - term use of versions with aluminium may increase the risk for getting osteoporosis . </P> <P> When excessive amounts of acids are produced in the stomach the natural mucous barrier that protects the lining of the stomach can damage the esophagus in people with acid reflux . Antacids contain alkaline ions that chemically neutralize stomach gastric acid, reducing damage and relieving pain . </P> <P> Antacids may be formulated with other active ingredients such as simethicone to control gas or alginic acid to act as a physical barrier to acid . </P>

What are antacids name two compounds which are used as antacid