Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2014 Publisher: The Boots Company PLC, 1 Thane Road West, Nottingham NG2 3AA Trading as: BCM
Bismuth has weak antacid properties. Bismuth subsalicylate may exert its antidiarrhoeal action not only by stimulating absorption of fluid and electrolytes across the intestinal wall but also when hydrolysed to salicylic acid, by inhibiting synthesis of a prostaglandin responsible for intestinal inflammation and hypermotility. In addition, bismuth subsalicylates binds toxins produced by E. coli.
Following oral administration, the amount of bismuth absorbed is negligible, whereas the salicylate component is absorbed completely and rapidly from the small intestine.
Bismuth subsalicylate is believed to be largely hydrolysed in the stomach to bismuth oxychloride and salicylic acid. In the small intestine non-dissociated bismuth subsalicylate reacts with other anions to form insoluble bismuth salts. In the colon, non-dissociated salicylate and other bismuth salts react with hydrogen sulphide to produce bismuth sulphide, a highly insoluble black salt responsible for blackening the tongue and faeces.
Bismuth is primarily excreted in the faeces, whereas the salicylate component is primarily excreted in the urine either as free salicylic acid or conjugated metabolites.
There are no preclinical data of relevance to the prescriber which are additional to that already included.
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