Singapore Drugs Database

Indication

The most common medical purpose for which bismuth subgallate is currently and formally indicated for is the use as a non-prescription internal deodorant product for the purpose of deodorizing flatulence and stools [L2309, L2312, A32566]. Additionally, there are also various non-prescription (over the counter) bismuth subgallate based wound healing products as well as ongoing studies into whether or not the substance can be utilized as a legitimate hemostatic agent - usually for soft tissue surgery in otorhinolaryngology and/or dermatologic settings [A32567, A32568, A32569, A32570]. Moreover, in the past bismuth subgallate may have seen some use as a treatment for Helicobacter pylori infection [A32571]. In contrast, contemporary first-line therapies generally involve proton pump inhibitor and antibiotic combination therapies that generally achieve high rates of pathogen eradication, ease of administration, and patient compliance.

Mechanism of Action

Bismuth salts exert their action largely in the upper gastrointestinal tract by way of local activity from luminal bismuth in the stomach and duodenum [A32571]. 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 [L2314]. Moreover, when bismuth subgallate is taken orally, various salts like bismuth citrate, bismuth oxychloride, and others are formed [A32571]. 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 [A32571]. 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 [A32571]. 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 [A32571]. 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 [L2312]. 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 [A32571]. Although the exact mechanism(s) of action by which bismuth compounds are able to elicit such antimicrobial effects remains unclear [A32571], 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 [A32571]. 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 [A32571]. 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 [A32572]. 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) [A32572, A32569]. 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 [A32572]. 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 [A32570, A32578]. 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 [A32567, A32569]. 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 [A32572] 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 [A32569]. Finally, bismuth subgallate also demonstrates a strong astringent ability [A32569] - 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 [L2314].

Pharmacokinetics

Absorption

Bismuth subgallate is only slightly, if at all, absorbed after oral ingestion [L2314]. The general human oral bioavailability of bismuth subgallate has been reported as low as 0.04% [L2314]. Any absorption that does occur is likely to happen from the upper small intestine [A32571]. The gastrointestinal absorption of bismuth from bismuth compounds demonstrates a large interindividual variation [L2314]. Factors affecting the absorption involve the formulation of the bismuth subgallate compound as well as the dietary factors of the individuals themselves [A32571]. Nevertheless, absorption can be enhanced with the concomitant intake of citrate and sulfhydryl-group-containing compounds [L2314]. Conversely, the simultaneous administration of antacids or a diet that is high in thiol content can lower absorption of bismuth subgallate [A32571].

Distribution

In general, oral administration is one of the most common routes of administration for non-prescription bismuth subgallate products and gastrointestinal and systemic absorption is usually very low.

Metabolism

No specific metabolism of bismuth is known [L2314]. In the kidney it induces the de novo synthesis of a bismuth-metal-binding protein, which is a kind of methallothionein [L2314].

Elimination

Clearance

On average, the blood clearance of the bismuth component of a bismuth salt like bismuth subgallate is within the range of 50 to 95 ml/min [A32583].

Toxicity

Depending on the level of severity of a patient's renal impairment, administration of bismuth compounds may not be appropriate as the reduced renal clearance can lead to undesirably elevated blood levels of bismuth [A32571]. Similarly, because of the biliary excretion of bismuth, severe liver disease may theoretically result in accumulation of bismuth as well [A32571]. Bismuth toxicity seemingly develops only from excessive dosage (perhaps from ingestion of bismuth over a prolonged time or intramuscular injections) and is characterized by nephrotoxicity, osteoarthropathy, encephalopathy, hepatotoxicity, stomatitis, and gingivitis [A32571]. However, the insoluble inorganic bismuth compounds are reported to be mainly associated with reversible encephalopathy [A32571]. In fact a number of studies have discussed how patients may experience a syndrome of subacute, progressive encephalopathy involving potential aphasia, myoclonous, and/or gait instability after taking bismuth subgallate in large quantities well over the usual recommended dosages [A32586, A32587]. This kind of encephalopathy is usually reversible with the discontinuation of the bismuth subgallate usage however [A32586, A32587].

Active Ingredient/Synonyms

basic bismuth 3,4,5-trihydroxybenzoate | basisches Wismutgallat | gallic acid bismuth basic salt | Wismutgallathydroxid | Bismuth subgallate |