Original Strength Pepcid AC acid reducer prevents heartburn associated with acid indigestion and sour stomach and relieves heartburn associated with acid indigestion and sour stomach brought on by eating or drinking certain food and beverages. Pepcid AC tablets can be taken as little as 15 minutes before your first bite for heartburn prevention*. . Original Strength Pepcid AC lasts all day or all night**.. It can cool the flare-up with relief that starts working in minutes***.* Prevents heartburn if taken 15 to 60 minutes before a meal.** Based on 9-hour acid control studies during the day and 12-hour acid control studies during the night. Acid control does not imply symptom relief.*** Pepcid AC starts to relieve heartburn in 15 to 30 minutes.