Pepto-Bismol is a registere trademark for an over-the-counter drug produced by the Procter and Gamble company used to treat minor digestive system upset. Its active ingredient is bismuth subsalicylate, which is also responsible for its distinctive pink color. The primary symptoms aided by Pepto-Bismol are nausea, heartburn, indigestion, upset stomach, diarrhea, and other temporary discomforts of the stomach and gastrointestinal tract.