Stomach acid is produced during the digestive process to break down food; it also kills bacteria. Sometimes there is an overproduction of acid, which erodes the lining of the esophagus, stomach, or small intestines, which can lead to ulcers. Famotidine belongs to the histamine blocker class, more precisely the histamine receptor-2 blocker class. Stomach acid is secreted when H-2 receptors present in the cell membranes of stomach cells are stimulated. By blocking these receptors, Famotidine reduces stomach acid production, which allows ulcers to heal more easily and prevents future ulcers from forming. Famotidine is available in an injectable solution or tablets, for the treatment of stomach ulcers, acid reflux, and gastritis in cats and dogs.