Bismuth citrate, colloidal

Widespread medicinal use of colloidal bismuth subcitrate (CBS) has prompted extensive studies of bismuth compounds involving the citrate anion. Bismuth citrate is essentially insoluble in water, but a dramatic increase in solubility with increasing pH has been exploited as a bio-ready source of soluble bismuth, a material referred to as CBS. Formulation of these solutions is complicated by the variability of the bismuth anion stoichiometry, the presence of potassium and/ or ammonium cations, the susceptibility of bismuth to oxygenation to Bi=0, and the incorporation of water in isolated solids. Consequently, a variety of formulas are classified in the literature as CBS. Solids isolated from various, often ill-defined combinations of bismuth citrate, citric acid, potassium hydroxide, or ammonium hydroxide have been assigned formulas on the basis of elemental analysis data or by determination of water and ammonia content, but are of low significance in the absence of complementary data other than thermal analysis (163), infrared spectroscopy (163), or NMR spectroscopy (164). In this context, the Merck index lists the chemical formula of CBS as KgfNHJaBieOafOHMCeHsCbh in the 11th edition (165), but in the most recent edition provides a less precise name, tripotassium dicitrato bismuthate (166). 

CBS = colloidal bismuth subcitrate RBC = ranitidine bismuth citrate approximate formulas. 

Paracelsus made the general introduction of several heavy metals into medicine in the 16th century and nowadays the particular use of bismuth compounds is focused upon the treatment of disorders of the alimentary system (14 such drugs are commonly prescribed in Britain). Several of these medicines are based upon a red viscous colloidal bismuth citrate solution containing ammonium hydroxide plus a colourant, a sweetening agent and emollients such as sorbitol or glycerine at pH = 10. 

Bismuth-containing preparations (e.g., those containing colloidal bismuth subcitrate) have effects similar to those of sucralfate, apparently because of their similar physical properties and coating effects. A combination of ranitidine-bismuth citrate is used with clarithromycin for eradication of H. pylori in the treatment and prevention of recurrence of duodenal ulcers. Combinations of bismuth subcitrate with other antibiotics and with H2 antihistamines also are used. Bismuth subsalicylate is used in this way as well. 

Salts of organic acids like bismuth citrate, gallate, lactate, salicylate, thioglycolate, or camphorate also exist as basic compounds. Bismuth subcitrate forms a colloidal solution with molecules of the formula [BixCOHlyfCgHsO ) ] depending on the acidity of the solution. Bismuth potassium tartrate and bismuth sodium tartrate are soluble in water, but with time they decompose [1,2,5,61. 

Interestingly, all of the elements in group 15 in the periodic table (N, P, As, Sb and Bi) are directly or indirectly related to the maintenance of human life as either essential elements (e.g., N and P) or therapeutic/toxic elements (e.g.. As, Sb and Bi). Currently antimony compounds (e.g., sodium stibogluconate, Pentostam ) are used clinically for the treatment of leishmaniasis and bismuth compounds (e.g., bismuth subsalicylate (BSS), colloidal bismuth subcitrate (CBS) and ranitidine bismuth citrate (RBC)) are widely used for the treatment of ulcer and Helicobacter pylori infection [l-3c,10,132,133]. Recently, clinical... 

Scheme 5.7 The basic BP citrate dimer found in the antiulcer drugs, colloidal bismuth subcitrate (CBS, DE-Nol ) and possibly ranitidine bismuth citrate. Assembly of these building block leads to the formation of polymeric anion.

Williams DR (1977) Analytical and computer simulation studies of a colloidal bismuth citrate system used as an ulcer treatment. J Inorg Nucl Chem 39 711-714 Li NC, White JM (1960) Some metal complexes of citrate-. 11 Anion exchange studies. J InorgNucl Chem 16 131-137... 

Asato E, Katsura K, Mikuriya M, Fujii T, Reedijk J (1993) Synthesis structure, and spectroscopic characterization of bismuth citrate compounds and bismuth-containing ulcer healing agent colloidal bismuth subcitrate (CBS). 3. Crystal and solution structures of KNH4[Bij(cit)j(H20)2] (HjO) (x=2,4). Inorg Chem 32 5322-5329... 

Colloidal bismuth compounds Subsalicylate and citrate salts available. OTC preparations popular and have some value in travelers diarrhea due to adsorption of toxins... 

For spectrophotometric lead determination the procedure normally used is the addition of sulfide to a solution, which results in the formation of a brown color due to the formation of colloidal lead sulfide. Ammonium, chloride, tartrates and citrates, as well as copper, bismuth, iron, and aluminum can cause interference. 

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