Rennie Extra Tablets Rennie Extra Tablets contain a powerful, long lasting formula that relieves the symptoms of heartburn & indigestion in just 2 minutes. The peppermint flavour chewable tablets work in two ways: Antacids quicky & effectively neutralise the excess acid in the stomach. Alginic acid forms a long lasting protective barrier in the stomach to stop acid escaping upwards, soothing that burning pain in your chest. Rennie Extra Tablets may be used during pregnancy & breastfeeding when used as directed.