Pepcid AC Original Strength Tablets, 30 Count, work to prevent or relieve heartburn and acid indigestion Containing the acid-reducer ingredient famotidine, these tablets control the production of excess stomach acid, preventing or relieving heartburn, acid indigestion, and upset or sour stomach brought on by eating or drinking certain food and beverages. You can take Pepcid AC to control stomach acid for up to 12 hours. Take Pepcid AC in as little as ten minutes before your first bite to prevent heartburn before it starts*.