Pepcid Complete combines an acid reducer (famotidine) with antacids (calcium carbonate and magnesium hydroxide) to relieve heartburn in two different ways: Acid reducers decrease the production of new stomach acid; antacids neutralize acid that is already in the stomach. The active ingredients in Pepcid Complete have been used for years to treat acid-related problems in millions of people safely and effectively. Just 1 tablet relieves heartburn due to acid indigestion.