Bismuth subsalicylate

Bismuth subsalicylate, with a chemical formula C7H5BiO4, is the active ingredient in the popular medication Pepto-Bismol that is used to treat nausea, heartburn, indigestion, upset stomach, diarrhea, and other temporary discomforts of the stomach and gastrointestinal tract. It is also the main ingredient of Kaopectate (since 2003, replacing attapulgite).

It displays anti-inflammatory action (due to salicylic acid) and also acts as an antacid and mild antibiotic.

It can also cause a black tongue and black stools in some users of the drug, when it combines with trace amounts of sulfur in their saliva and gastrointestinal tract. This discoloration is temporary and harmless.

Children should not take medication with Bismuth subsalicylate while recovering from the flu or chicken pox, as epidemiologic evidence points to an association between the use of salicylate containing medications during certain viral infections and the onset of Reye's syndrome.