Bismuth subgallate

Bismuth salts exert their action largely in the upper gastrointestinal tract by way of local activity from luminal bismuth in the stomach and duodenum.

In terms of bismuth subgallate's ability to deodorize flatulence and stools as an internal deodorant - although not fully elucidated - it is believed that when the substance is administered orally, its relative insolubility and poor absorption allows it to remain within the gastrointestinal lumen and inhibit colonic bacteria from acting on fermentable food residues in the GI tract.

Moreover, when bismuth subgallate is taken orally, various salts like bismuth citrate, bismuth oxychloride, and others are formed. These salts are then taken up into surrounding gastric mucus as well as bound to protein within the base of any ulcers that may be present after coming into contact with gastric juice. Additionally, bismuth compounds like bismuth subgallate are also believed to have the capacity to trigger the secretion of prostaglandins, epithelial growth factor (EGF), and mucosal bicarbonate as a means to inhibit the action of pepsin in gastric juice. These actions subsequently protect gastric mucous from peptic luminal degradation as well as enhance the properties of mucous to assist in the healing of both duodenal and gastric ulcers. In this way, bismuth subgallate works to absorb extra water and/or toxins in the large intestine, allowing it to form a protective coat on the intestinal mucosa and over ulcers that may or may not be associated with infections like those of Helicobacter pylori.

Furthermore, studies have shown that bismuth compounds like bismuth subgallate are capable of demonstrating antimicrobial effects against various gastrointestinal tract pathogens like E. coli, Salmonella, Shigella, Vibrio cholera, Campylobacter jejuni, H. pylori, and some enteric viruses like Rotaviruses. Although the exact mechanism(s) of action by which bismuth compounds are able to elicit such antimicrobial effects remains unclear, a number of experimental observations suggest that bismuth has been able to complex with the bacterial wall and periplasmic membrane; inhibit bacterial enzymes like urease, catalase, and lipase; inhibit bacterial protein and ATP synthesis; and also inhibit or decrease the adherence of bacteria like H. pylori to epithelial cells. In essence, ultrastructural studies have shown evidence of the binding of bismuth complexes to the bacterial wall and periplasmic space between the inner and outer bacterial membrane of H.pylori with subsequent ballooning and disintegration of the pathogen. To various extents, these antimicrobial actions may also illustrate how bismuth subgallate is capable of neutralizing colonic bacteria from acting on fermentable foods as well.

Numerous studies have and continue to study the possible hemostatic action that bismuth subgallate may have. As the bismuth salt of gallic acid, bismuth subgallate's chemical structure shares similarities to ellagic acid, another gallic acid derivative. Ellagic acid itself is a clot-promoting agent that initiates thrombin formation by way of the intrinsic pathway via an action on Hageman factor (clotting factor XII). It is believed that bismuth subgallate's ability to activate factor XII is associated with the chemical's negatively charged moieties - whose contact with factor XII would theoretically initiate the intrinsic pathway to blood clotting.

Other studies have also suggested that bismuth subgallate is capable of inducing macrophages to secrete growth factors to facilitate wound healing, decreasing lesion area, enhancing granulation tissue formation and re-epithelialization, the initiation of the proliferation of collagen via the activation of fibroblasts, the accelerated re-establishment of blood vessels, and also the restriction of nitric oxide formation.

Given such studies regarding bismuth subgallate's potential hemostatic abilities, there has been and continues to be interest in indicating the agent for use in otolaryngology as in tonsillectomies or adenotonsillectomies to achieve reduced bleeding and surgery times; topical treatment in various open wound surgeries to facilitate faster and earlier clotting between tissues; ileostomy; dental surgeries; epistaxis management; among others. Nevertheless, study results are conflicting; where there may be experimental results suggesting some improvements in reduced operation time and operative blood loss when bismuth subgallate is used as a hemostatic agent in tonsillectomies there are also study results that observed bismuth subgallate having a negative influence on the healing processes of wounds inflicted in animal models, in which the use of the agent actually delayed the rate of new vessel formation and optimal wound healing.

Finally, bismuth subgallate also demonstrates a strong astringent ability - an action that can facilitate both its deodorant and hemostatic effects and assists in its indication as an active ingredient in a number of non-prescription products for hemorrhoid suppositories or topical applications, diarrhea, etc.