Rennie Peppermint tablets offer quick relief from heartburn and indigestion. Rennie is always by your side, no matter where you are or what you are doing, day or night. Whether you suffer from acid reflux at work and struggle to be productive, or if you, like many others, have difficulties sleeping due to burning feelings at night, the fast-acting antacids in Rennie chewable tablets neutralize excess stomach acid and allow you to relax. The two active components are magnesium carbonate and calcium carbonate.