Hate when heartburn hits at the worst times? Alka-Seltzer Extra Strength Antacid Relief Chews are your go to for fast on-the-go heartburn relief. Conveniently sized, with Alka-Seltzer Extra Strength Heartburn Relief Chews, acid indigestion relief is always within reach. Non-gritty and non-chalky, these chewable tablets contain the active ingredient Calcium carbonate. To use: Adults and children 12 years old and over: fully chew then swallow 2 to 4 chewable tablets as symptoms occur, or as directed by a doctor. Do not take more than 6 tablets in 24 hours. If pregnant or breast-feeding, inform your doctor that you are using this product.