calcium carbonate,saccharin,simethicone An antacid is a compound that absorbs and neutralizes stomach acid. The use of antacids has declined because of the availability of many very potent drugs that are more effective and much less troublesome to take than antacids. Still, these drugs can be helpful in relieving intermittent, infrequent heartburn and indigestion. If these symptoms occur frequently such as multiple times a day or at night, then the cause should be sought, as a more serious disorder may be present. Calcium carbonate is a mineral. Saccharin is a synthetic sweetening agent. Simethicone is a defoaming agent that breaks down small bubbles in the stomach, allowing the swallowed air to be more readily belched up. Some facts about antacids are as follows: Taken on an empty stomach, they only neutralize acid for 30 to 60 minutes because the antacid quickly leaves the stomach. If taken with food, the protective effect may be 2 or 3 hours. To get as much acid reduction as prescription medicines produce is expensive as the antacid must be taken frequently during the day and night. It is probably cheaper to take an acid-reducing pill once or twice a day. All antacids, but especially calcium carbonate, can result in an acid rebound effect where the stomach acid surges back after the antacid has left the stomach, another reason for long-acting medications.