Antacids neutralize stomach acid, though depending on brand and type they differ greatly in their reaction time and neutralizing capacity.
Veterinarians sometimes use antacids to prevent and treat dog stomach disorders and to lower high phosphorous levels in animals with kidney failure.
Calcium carbonate is the active ingredient in many popular over-the-counter antacids. Calcium based antacids are usually inexpensive and may provide a beneficial source of calcium. Unlike aluminum or magnesium based antacids however, calcium based antacids stimulate the release of the hormone gastrin from the stomach. Since gastrin stimulates acid secretion in the stomach, over-use of calcium based antacids may cause acid rebound.