24 tablets. Fast effective relief from indigestion and heartburn. Rennie Peppermint tablets contain two naturally-occurring antacids called calcium carbonate and magnesium carbonate which neutralise excess stomach acid by turning it into water & other natural substances. Calcium carbonate acts directly in the oesophagus, as well as the stomach, and both antacids are then eliminated by your body. Indications: Rennie relieves acid indigestion, heartburn, nervous indigestion, acidity, flatulence, upset stomach, dyspepsia or biliousness.