Setlers antacid tablets contain the active ingredient calcium carbonate, which is a type of medicine called an antacid. Antacids are used to reduce the acidity of the stomach's juices. Stomach acid is produced in the stomach as a normal part of the digestive process. However, too much stomach acid can cause symptoms such as heartburn and indigestion. It can also irritate an inflamed stomach lining or an ulcer in the stomach or intestine (peptic ulcer). Calcium carbonate works by binding to and neutralising excess acid produced by the stomach. This helps to relieve the pain and discomfort of indigestion, heartburn and other symptoms related to excess stomach acid. Antacids work as soon as they reach the stomach.