Bismuth subcitrate acts via multiple mechanisms to exert its gastroprotective and antimicrobial effects. Under the effect of gastric acid, a precipitate is formed from tripotassium dicitrato bismuthate, which coats the ulcer crater and protects it from further acid and pepsin attack. The compound also inhibits the activity of pepsin, a proteolytic enzyme that can exacerbate ulcer formation. Bismuth subcitrate exerts its gastric protection through both prostaglandin-mediated and non-prostaglandin-mediated mechanisms. It stimulates the production of endogenous prostaglandins, which enhance mucosal blood flow, stimulate mucus and bicarbonate secretion, and promote epithelial cell proliferation. In addition to its mucosal protective effects, bismuth subcitrate has a direct bactericidal effect on Helicobacter pylori. It also functions as a metallo-β-lactamase inhibitor. Bismuth can replace zinc(II) from enzymes such as metallo-β-lactamases, thereby inhibiting their activity. Once internalized by cells, bismuth subcitrate follows a complex intracellular trafficking pathway involving endosomes, lysosomes, microtubules, and the Golgi apparatus. The compound also stimulates oxidative stress, altering glutathione and cysteine metabolism, leading to the formation of black bismuth sulfide particles.

In vitro, bismuth subcitrate exhibits antimicrobial activity against Helicobacter pylori, with a direct bactericidal effect that contributes to its efficacy in eradicating this pathogen. The compound's cytoprotective action is demonstrated in cell culture models using gastric epithelial cell lines, where it protects cells from damage induced by acid, bile salts, and other noxious agents. In vitro studies have also shown that bismuth subcitrate can inhibit the activity of various enzymes, including metallo-β-lactamases, by replacing zinc ions in the active site. The compound's ability to form a protective barrier on the gastric mucosa has been demonstrated in vitro using artificial gastric mucus models. Additionally, bismuth subcitrate has been studied for its effects on cellular pathways, including its ability to stimulate oxidative stress and alter glutathione and cysteine metabolism in renal cells. These in vitro findings provide a mechanistic basis for the compound's gastroprotective and antimicrobial effects.

In vivo, bismuth subcitrate has been extensively studied in animal models and clinical settings for its efficacy in treating gastric and duodenal ulcers. The compound is 2- to 20-fold more potent than sucralfate in rodent gastric lesion models, demonstrating superior mucosal protection and ulcer healing properties. In H. pylori-infected animal models, bismuth subcitrate reduces bacterial colonization and promotes ulcer healing. In clinical studies, combination therapy with bismuth subcitrate, antibiotics, and a proton pump inhibitor has been shown to achieve H. pylori eradication rates of 80-90%. The compound also reduces ulcer relapse rates by approximately 31 percentage points compared to ranitidine at 12 months. In vivo, bismuth subcitrate exerts a local action on the gastric mucosa, with only small amounts of bismuth being absorbed (less than 0.2% of the dose) during therapy. The compound's efficacy in treating peptic ulcers and its role in H. pylori eradication have made it a valuable component of gastrointestinal pharmacotherapy.

In vitro enzyme/receptor binding studies are not typical for bismuth subcitrate, as its primary mechanism of action is based on physicochemical and antimicrobial properties rather than receptor binding. However, enzyme inhibition assays have been conducted to evaluate its effects on metallo-β-lactamases. In these assays, bismuth subcitrate is incubated with the enzyme in the presence of a chromogenic or fluorogenic substrate, and the inhibition of enzyme activity is measured spectrophotometrically. The compound's ability to replace zinc ions from the enzyme active site is assessed using techniques such as inductively coupled plasma mass spectrometry (ICP-MS) or atomic absorption spectroscopy. For studies on pepsin inhibition, the enzyme is incubated with bismuth subcitrate and a protein substrate, and the extent of proteolysis is measured. These enzyme assays provide insights into the molecular mechanisms underlying the compound's antimicrobial and gastroprotective effects.

In vitro cell-based assays for bismuth subcitrate are conducted using gastric epithelial cell lines, such as AGS or MKN-45 cells, to evaluate its cytoprotective effects. Cells are cultured in appropriate media and treated with bismuth subcitrate at various concentrations, then exposed to damaging agents such as acid, ethanol, or bile salts. Cell viability is assessed using MTT or LDH release assays, and the extent of cytoprotection is calculated. In renal cell models, the compound's intracellular trafficking and metabolic fate are studied using fluorescently labeled bismuth subcitrate or by measuring bismuth accumulation using ICP-MS. Oxidative stress is evaluated by measuring reactive oxygen species (ROS) production using fluorescent probes such as DCFH-DA, and glutathione and cysteine metabolism are assessed using biochemical assays. These cell-based assays provide critical information on the compound's cellular effects and its potential for toxicity in non-target tissues.

In vivo animal experiments for bismuth subcitrate are conducted in rodent models of gastric ulcers, such as the indomethacin-induced, ethanol-induced, or stress-induced ulcer models. Animals are treated with bismuth subcitrate orally at various doses, and ulcer indices are calculated based on the number and severity of gastric lesions. The compound's effect on gastric acid secretion is assessed by measuring gastric pH and acid output. In H. pylori-infected animal models, bacterial colonization is quantified by culture or PCR, and the extent of gastritis is evaluated histologically. Pharmacokinetic studies in animals involve administering radiolabeled bismuth subcitrate and measuring bismuth levels in blood, tissues, and excreta using ICP-MS or atomic absorption spectroscopy. These animal studies are essential for establishing the compound's efficacy, safety, and pharmacokinetic profile.

Absorption, Distribution and Excretion
Following ingestion of colloidal bismuth citrate (214 mg bismuth), the mean peak concentration of bismuth in whole blood exceeded 50 mg/L, reaching its peak at 30 minutes. However, after ingestion of bismuth nitrate (205 mg bismuth), no evidence of bismuth absorption into the blood was observed, although baseline blood bismuth levels remained elevated in three volunteers who took bismuth nitrate one week after taking colloidal bismuth citrate. The mean plasma concentration in all five volunteers was assessed 45 minutes after administration of colloidal bismuth subcitrate, yielding a concentration of 79.76 μg/L, compared to a blood concentration of 47.6 μg/L. Bismuth is primarily excreted via urine and bile. Renal excretion appeared to reach steady state after 2 weeks of discontinuation, with similar rates observed after 6 weeks. In the first two weeks after discontinuation, the mean urinary excretion rate of bismuth was 2.6% per day (urinary drug concentration ranging from 24 to 250 μg/mL), indicating accumulation in tissues and slow excretion.

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Biological Half-Life
The elimination half-life of bismuth is approximately 5 days.

Bismuth subcitrate is poorly absorbed from the gastrointestinal tract; less than 1% of an oral dose is absorbed. Absorbed bismuth is distributed to various tissues, including the kidneys, liver, and bone, and is excreted primarily in urine. The compound's poor absorption contributes to its favorable safety profile, as systemic exposure is minimal. The small fraction of absorbed bismuth binds to plasma proteins and is slowly eliminated, with a terminal half-life of several days. Bismuth subcitrate is not significantly metabolized; the bismuth ion remains in its inorganic form. The compound's pharmacokinetics are characterized by low systemic bioavailability and predominantly fecal excretion of unabsorbed bismuth. The lack of significant systemic absorption makes bismuth subcitrate a locally acting agent, which is advantageous for minimizing systemic side effects.

Protein Binding
90%
Bismuth subcitrate has a relatively low toxicity profile compared to other bismuth compounds. Common side effects include darkening of the tongue and stool, which are harmless and reversible upon discontinuation of the drug. Rarely, bismuth encephalopathy, a serious neurological condition characterized by confusion, ataxia, and myoclonus, can occur with prolonged high-dose use, particularly in patients with renal impairment. The compound's low systemic absorption minimizes the risk of systemic toxicity, but caution is advised in patients with renal insufficiency. In vitro studies have shown that bismuth subcitrate can stimulate oxidative stress and alter glutathione and cysteine metabolism in renal cells, with implications for renal toxicity. The compound binds to transferrin and follows a complex intracellular trafficking pathway involving endosomes and lysosomes. Preclinical toxicity studies have demonstrated that bismuth subcitrate is well-tolerated at therapeutic doses, with no significant genotoxicity or carcinogenicity.

Bismuth compounds used to treat peptic ulcers and gastroesophageal reflux disease (GORD). Bismuth subcitrate is a mineral compound used to treat duodenal and gastric ulcers caused by Helicobacter pylori. Bismuth subcitrate potassium is a soluble complex bismuth salt used in combination with metronidazole and tetracycline to treat gastric ulcers caused by Helicobacter pylori infection.

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Drug Indications
For the treatment of peptic ulcers and gastroesophageal reflux disease (GORD). For the treatment of inflammatory and erosive ulcerative diseases of the gastric and duodenal mucosa: gastritis, gastric and duodenal ulcers, functional non-ulcer dyspepsia, erosive duodenitis, postoperative inflammation and erosive changes—anastomotic stomatitis, anastomotic peptic ulcers.

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Mechanism of Action
Colloidal bismuth subcitrate is very effective in treating gastroduodenal diseases, and its mechanism of action appears to be multifaceted. It has little to no acid-neutralizing effect and does not affect gastric acid secretion. It is currently uncertain whether it affects pepsin secretion, but it does inhibit pepsin activity. It increases the secretion of mucoglycoproteins and may bind to the gastric mucus layer, thus preventing hydrochloric acid diffusion. It accelerates ulcer healing and leads to the accumulation of epidermal growth factor around ulcers. Furthermore, it has cytoprotective effects and increases the secretion of mucosal prostaglandins and bicarbonate. It has bactericidal activity against Helicobacter pylori (associated with gastritis and peptic ulcers). It also prevents Helicobacter pylori from adhering to epithelial cells and inhibits enzymes secreted by Helicobacter pylori, such as proteases, lipases, glycosidases, and phospholipases.

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Pharmacodynamics
Bismuth citrate is very effective in treating gastroduodenal diseases, and its mechanism of action appears to be multifaceted. It has little to no acid-neutralizing effect and does not affect gastric acid secretion.
Bismuth subcitrate is used clinically in combination with antibiotics (metronidazole and tetracycline) and a proton pump inhibitor for Helicobacter pylori eradication therapy. It is also used as a monotherapy for the treatment of peptic ulcers and dyspepsia. The compound is available in many countries worldwide under various brand names, including De-Nol®, Gastrodenol®, and Ulcerone®. Its unique combination of high acid stability, potent cytoprotective action, and direct bactericidal effect on H. pylori distinguishes it from other gastroprotective agents. Bismuth subcitrate is a component of the Maastricht consensus-recommended regimens for H. pylori eradication. The compound has been extensively studied in clinical trials and has a well-established safety and efficacy profile. It remains an important therapeutic option for the management of gastrointestinal disorders, particularly in regions where H. pylori infection is prevalent.

C12H10BIK3O14

704.4747

703.878

57644-54-9

10101269

White to off-white solid powder

309.6ºC at 760 mmHg

155.2ºC

2

14

4

30

211

0

ZQUAVILLCXTKTF-UHFFFAOYSA-H

InChI=1S/2C6H8O7.Bi.3K/c2*7-3(8)1-6(13,5(11)12)2-4(9)10;;;;/h2*13H,1-2H2,(H,7,8)(H,9,10)(H,11,12);;;;/q;;+3;3*+1/p-6

bismuth;tripotassium;2-hydroxypropane-1,2,3-tricarboxylate

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : ~100 mg/mL (~141.95 mM)

Solubility in Formulation 1: 100 mg/mL (141.95 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)