Pepto-Bismol vs Tum: Difference Between Tums and Pepto-BismolBismuth SubsalicylateRegarding Pepto-Bismol vs Tum: Difference Between Tums and Pepto-Bismol. Tums contain calcium carbonate, providing quick relief from heartburn and acid indigestion, while Pepto-Bismol features bismuth subsalicylate, effectively treating nausea, diarrhea, and upset stomach.