Bismuth toxicity--a reassessment

Bismuth in Radical Chemistry and Catalysis

Whereas indications of radical reactivity in bismuth compounds can be traced back to the 19th century, the preparation and characterization of both transient and persistent bismuth-radical species has only been established in recent decades. These advancements led to the emergence of the field of bismuth radical chemistry, mirroring the progress seen for other main-group elements. The seminal and fundamental studies in this area have ultimately paved the way for the development of catalytic methodologies involving bismuth-radical intermediates, a promising approach that remains largely untapped in the broad landscape of synthetic organic chemistry. In this review, we delve into the milestones that eventually led to the present state-of-the-art in the field of radical bismuth chemistry. Our focus aims at outlining the intrinsic discoveries in fundamental inorganic/organometallic chemistry and contextualizing their practical applications in organic synthesis and catalysis.

Bioactive Bismuth Compounds: Is Their Toxicity a Barrier to Therapeutic Use?

Bismuth compounds are considered relatively non-toxic, with their low solubility in aqueous solutions (e.g., biological fluids) being the major contributing factor to this property. Bismuth derivatives are widely used for the treatment of peptic ulcers, functional dyspepsia, and chronic gastritis. Moreover, the properties of bismuth compounds have also been extensively explored in two main fields of action: antimicrobial and anticancer. Despite the clinical interest of bismuth-based drugs, several side effects have also been reported. In fact, excessive acute ingestion of bismuth, or abuse for an extended period of time, can lead to toxicity. However, evidence has demonstrated that the discontinuation of these compounds usually reverses their toxic effects. Notwithstanding, the continuously growing use of bismuth products suggests that it is indeed part of our environment and our daily lives, which urges a more in-depth review and investigation into its possible undesired activities. Therefore, this review aims to update the pharmaco-toxicological properties of bismuth compounds. A special focus will be given to in vitro, in vivo, and clinical studies exploring their toxicity.

Heavy Metal-Based Nanoparticles as High-Performance X-ray Computed Tomography Contrast Agents

X-ray computed tomography (CT) contrast agents offer extremely valuable tools and techniques in diagnostics via contrast enhancements. Heavy metal-based nanoparticles (NPs) can provide high contrast in CT images due to the high density of heavy metal atoms with high X-ray attenuation coefficients that exceed that of iodine (I), which is currently used in hydrophilic organic CT contrast agents. Nontoxicity and colloidal stability are vital characteristics in designing heavy metal-based NPs as CT contrast agents. In addition, a small particle size is desirable for in vivo renal excretion. In vitro phantom imaging studies have been performed to obtain X-ray attenuation efficiency, which is a critical parameter for CT contrast agents, and the imaging performance of CT contrast agents has been demonstrated via in vivo experiments. In this review, we focus on the in vitro and in vivo studies of various heavy metal-based NPs in pure metallic or chemical forms, including Au, Pt, Pd, Ag, Ce, Gd, Dy, Ho, Yb, Ta, W, and Bi, and provide an outlook on their use as high-performance CT contrast agents.

Effects of Bismuth Exposure on the Human Kidney-A Systematic Review

The effects of bismuth toxicity on the kidney-the main organ responsible for blood filtration-were systematically reviewed. This review was motivated by availability of several sources of bismuth in contact with humans including environmental, medications, dental materials, and cosmetics, potentially leading to kidney filtration of this chemical. No previous studies have systematically reviewed the literature considering this association. A total of 22 studies with a total of 46 individuals met the inclusion criteria, 19 being case reports with only one patient enrolled. The included studies publication dates ranged from 1961 to 2021 and the countries of publication were the United States of America, United Kingdom, Germany, Turkey, Switzerland, and Canada. Bismuth sources affecting the kidneys were uniquely reported as from medical purposes and mostly associated to overdoses with several symptoms, apparently with dose-dependent consequences. Patient history of renal impairment seemed to affect the outcome of the case. Several therapies were conducted following bismuth intoxication, and few studies performed renal biopsies describing its histological findings. It is crucial to reconsider the nephrotoxicity of bismuth compounds, mainly in patients with previous history of renal impairment.

Efficacy and safety of high-dose esomeprazole-amoxicillin dual therapy for Helicobacter pylori rescue treatment: a multicenter, prospective, randomized, controlled trial

BACKGROUND

High-dose dual therapy (HDDT) with proton pump inhibitors (PPIs) and amoxicillin has attracted widespread attention due to its favorable efficacy in eradicating Helicobacter pylori (H. pylori). This study aimed to compare the efficacy and safety of high-dose PPI-amoxicillin dual therapy and bismuth-containing quadruple therapy for H. pylori rescue treatment.

METHODS

This was a prospective, randomized, multicenter, non-inferiority trial. Patients recruited from eight centers who had failed previous treatment were randomly (1:1) allocated to two eradication groups: HDDT (esomeprazole 40 mg and amoxicillin 1000 mg three times daily; the HDDT group) and bismuth-containing quadruple therapy (esomeprazole 40 mg, bismuth potassium citrate 220 mg, and furazolidone 100 mg twice daily, combined with tetracycline 500 mg three times daily; the tetracycline, furazolidone, esomeprazole, and bismuth [TFEB] group) for 14 days. The primary endpoint was the H. pylori eradication rate. The secondary endpoints were adverse effects, symptom improvement rates, and patient compliance.

RESULTS

A total of 658 patients who met the criteria were enrolled in this study. The HDDT group achieved eradication rates of 75.4% (248/329), 81.0% (248/306), and 81.3% (248/305) asdetermined by the intention-to-treat (ITT), modified intention-to-treat (MITT), and per-protocol (PP) analyses, respectively. The eradication rates were similar to those in the TFEB group: 78.1% (257/329), 84.2% (257/305), and 85.1% (257/302). The lower 95% confidence interval boundary (-9.19% in the ITT analysis, - 9.21% in the MITT analysis, and -9.73% in the PP analysis) was greater than the predefined non-inferiority margin of -10%, establishing a non-inferiority of the HDDT group vs. the TFEB group. The incidence of adverse events in the HDDT group was significantly lower than that in the TFEB group (11.1% vs. 26.8%, P  < 0.001). Symptom improvement rates and patients' compliance were similar between the two groups.

CONCLUSIONS

Fourteen-day HDDT is non-inferior to bismuth-containing quadruple therapy, with fewer adverse effects and good treatment compliance, suggesting HDDT as an alternative for H. pylori rescue treatment in the local region.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT04678492.

Diagnosis and Management of Microscopic Colitis in Pediatric Patients

Microscopic colitis (MC) is an inflammatory disease of the colon, characterized by chronic watery diarrhea with distinguishing histologic findings despite normal endoscopic appearance of the colonic mucosa. MC is a common cause of diarrhea in older adults, though it has been infrequently reported in children and adolescents. As MC is rare in the pediatric population, and the clinical presentation is non-specific, increased awareness of this disease amongst pediatric clinicians and pathologists is essential for timely diagnosis, which requires performing colonoscopy with biopsy. The etiology of MC is incompletely understood, but current theories in pathogenesis inform management strategies. The goals of management in pediatric MC should be to achieve symptomatic improvement while minimizing adverse effects of treatment. Many patients who achieve clinical response have symptomatic recurrence after discontinuation of initial therapy, and may require maintenance medication therapy to sustain remission. This review aims to summarize the epidemiology and risk factors, clinical features, diagnosis, theories regarding pathogenesis, and suggested management approaches for MC in the pediatric population.

Microscopic colitis

Microscopic colitis (MC) is an inflammatory disease of the large intestine associated with urgent watery diarrhoea. MC may occur in people of all ages, although the disease primarily affects older women. Once believed to be rare, MC is now known to be a common cause of chronic watery diarrhoea in high-income countries, affecting 1 in 115 women and 1 in 286 men during their lifetime in Swedish population-based estimates. An inappropriate immune response to disturbances in the gut microenvironment is implicated in the pathogenesis of MC. Evidence also supports an underlying genetic basis for disease. The diagnosis of MC relies on clinical symptoms and microscopic assessment of colonic biopsy samples. MC is categorized histologically into collagenous colitis, lymphocytic colitis and their incomplete forms. The mainstay of treatment includes the use of budesonide, with or without adjunctive therapies, and withdrawal of offending drugs. Emerging studies suggest a role for biologicals and immunosuppressive therapies for the management of budesonide-refractory or budesonide-dependent disease. MC can have a substantial negative effect on patient quality of life. The outlook for MC includes a better understanding of the immune response, genetics and the microbiome in disease pathogenesis along with progress in disease management through robust clinical trials.

Patterns of quadruple therapy use including bismuth for Helicobacter pylori eradication: A cohort study in the French national claims database

BACKGROUND

Quadruple therapy using a single capsule formulation of bismuth, metronidazole and tetracycline (BMT; Pylera®), associated with omeprazole for the eradication of Helicobacter pylori, represents the reintroduction of bismuth in France after 40 years.

OBJECTIVE

To describe the real-life patterns of use of BMT following a request from the French health authorities.

METHODS

Patients with a first BMT dispensing (index date, ID), with one year of data before and after ID, were identified in the French nationwide claims database 1/97 sample. Misuse of BMT was defined as dispensing>1 pack of BMT at ID or absence of a diagnostic test in the preceding year.

RESULTS

In total, 540 patients were included. Prescribers were gastroenterologists (n=243; 45%) and general practitioners (n=160; 30%). A proton pump inhibitor was co-dispensed to 504 patients (96%). Ten patients (2%) had contraindications to BMT. Fifty-nine patients (11%) met the misuse criteria: ten (2%) were dispensed>1 pack of BMT and 49 (9%) had not had a diagnostic test for H. pylori in the previous year. During follow-up, 27 patients (5%) required retreatment (treatment failure).

CONCLUSION

In this real-life study, most patients were dispensed only one pack of BMT, consistent with recommendations. Misuse related principally to the absence of prior diagnostic test for H. pylori.

Derivation of biomonitoring equivalents (BE values) for bismuth

Bismuth (Bi) is a natural element present in the environmental media. Bismuth has been used medicinally for centuries, specifically for the treatment of gastrointestinal (GI) disorders. Although bismuth toxicity is rare in humans, an outbreak of bismuth-induced neurotoxicity was reported in France and Australia in the mid-1970s. The primary source of bismuth exposure in the general population is via food. US FDA (2019) estimated recommended daily intake (RDI) for bismuth as 848 mg bismuth/day (12.1 mg Bi/kg-d assuming a body weight of 70 kg) for GI tract disorders. Exposures to bismuth can be quantified by measuring concentrations in blood and urine. Biomonitoring equivalents (BEs) were derived based on US FDA's RDI as a tool for interpretation of population-level biomonitoring data. A regression between steady state plasma concentrations and oral intakes was used to derive plasma BEs. A whole blood: plasma partitioning coefficient of 0.6 was used to convert plasma BE into whole blood BE. A mass balance equation with a urinary excretion fraction of 0.0003 was used to derive urinary BE. The BE values associated with US FDA's RDI for plasma, whole blood and urine were 8.0, 4.8 and 0.18 μg/L, respectively. These BE values together with bismuth biomonitoring data may be used in screening and prioritization of health risk assessment of bismuth in the general population.

Ethyl acetate extract of Kaempferia parviflora inhibits Helicobacter pylori-associated mammalian cell inflammation by regulating proinflammatory cytokine expression and leukocyte chemotaxis

BACKGROUND

Kaempferia parviflora (KP) has been used in traditional Thai medicine to cure gastrointestinal disorders since ancient times. Helicobacter pylori is an initiating factor in gastric pathogenesis via activation of massive inflammation, the cumulative effect of which leads to gastric disease progression, including gastric carcinogenesis. Accordingly, the effect of a crude ethyl acetate extract of KP (CEAE-KP) on proinflammatory cytokine production and cell chemotaxis was the focus of this study.

METHODS

The cytotoxicity of CEAE-KP (8-128 μg/ml) on AGS (gastric adenocarcinoma) cells was determined at 6, 12 and 24 h using an MTT assay. The effect of CEAE-KP on H. pylori-induced interleukin (IL)-8 production by AGS cells was evaluated by ELISA and RT-PCR. The effect of CEAE-KP on monocyte and neutrophil chemotaxis to H. pylori soluble protein (sHP) and IL-8, respectively, was determined using a Boyden chamber assay with THP-1 or HL-60 cells.

RESULTS

CEAE-KP reduced AGS cell viability in a concentration- and time-dependent manner, but at 8-16 μg/ml, it was not cytotoxic after 6-24 h of exposure. Coculture of AGS cells with CEAE-KP at a noncytotoxic concentration of 16 μg/ml and H. pylori reduced IL-8 secretion by ~ 60% at 12 h, which was consistent with the decreased level of mRNA expression, and inhibited neutrophil chemotaxis to IL-8. sHP (100 ng/ml) induced marked monocyte chemoattraction, and this was decreased by ~ 60% by CEAE-KP.

CONCLUSION

CEAE-KP might serve as a potent alternative medicine to ameliorate the inflammation mediated by H. pylori infection.

Bismuth Concentrations in Patients Treated in Real-Life Practice with a Bismuth Subcitrate-Metronidazole-Tetracycline Preparation: The SAPHARY Study

INTRODUCTION

A fixed-dose association of bismuth subcitrate, metronidazole and tetracycline (BMT) (Pylera^®, Allergan, NJ, USA) was made available in France in 2013 for the eradication of Helicobacter pylori. Due to a historical issue of bismuth encephalopathy, the French Health Authorities requested a study of blood and plasma bismuth concentrations with BMT in daily practice.

AIMS

The aim of the study was to measure eventual bismuth accumulation and neurological toxicity in patients prescribed BMT.

METHODS

Patients initiating BMT for H. pylori between March 2014 and December 2015 were included. A blood sample was taken before first BMT intake and 24 h after the last intake, for assay of bismuth. A concentration > 50 μg/L was considered abnormal. Neurological complaints were assessed at inclusion, at the end of the 10-day treatment course, and 28 days later.

RESULTS

202 patients were included, of whom 190 took at least one dose of BMT, and 167 provided both required blood samples. Mean blood bismuth concentrations after the BMT course were 16.9 μg/L (95% confidence interval 15.6-18.3). Concentrations were > 50 μg/L (56.0 μg/L and 50.9 μg/L) in two elderly patients, one of whom presented mild, transient memory impairment during treatment. Non-serious neurological symptoms occurred in 20% of all patients and treatment failure was documented in 5% of patients.

CONCLUSIONS

In this study measuring blood bismuth concentrations in real-life practice, in < 1% of patients the BMT course resulted in blood bismuth concentrations > 50 μg/L. No serious neurological adverse events were observed.

STUDY REGISTRATION

EU-PAS register EUPAS3142 at www.encepp.eu ; ENCePP study seal.

Synthesis and Color Evaluation of Ta5+-Doped Bi2O3

Ta⁵⁺-doped Bi₂O₃ solid solutions, (Bi_1-x Ta _x )₂O_3+2x (0 ≤ x ≤ 0.20), were synthesized by a conventional solid-state reaction method. The crystal structure, optical properties, and color of the pigments were characterized. The (Bi_1-x Ta _x )₂O_3+2x (x = 0, 0.03, 0.04, 0.20) samples were obtained in a single-phase form, and the crystal structure depended on the Ta content; they were monoclinic α-phase (x = 0), tetragonal β-phase (x = 0.03, 0.04), and cubic δ-phase (x = 0.20). Among them, (Bi_0.97Ta_0.03)₂O_3.06 strongly absorbed visible light at the wavelength shorter than 480 nm and exhibited the most vivid orange color. The redness value (a*) was comparable to that of commercial orange pigments, and the yellowness value (b*) was slightly larger. Although it is necessary to improve chemical stability, the (Bi_0.97Ta_0.03)₂O_3.06 pigment has potential for an environmentally friendly inorganic orange pigment.

An Update on Drug-Induced Pigmentation

Drug-induced pigmentation accounts for up to 20% of all cases of acquired pigmentation. A thorough review of medical history and previous and ongoing medications as well as a complete skin examination can guide diagnosis. Implicated agents include alkylating/cytotoxic agents, analgesics, antiarrhythmics, anticoagulants, antiepileptics, antimalarials, antimicrobials, antiretrovirals, metals, prostaglandin analogs, and psychotropic agents, among others. Confirming true drug associations can be challenging, especially in the setting of delayed onset of pigmentation and coexisting polypharmacy.

High toxicity of Bi(OH)3 and α-Bi2O3 nanoparticles towards malignant 9L and MCF-7 cells

Here we report the extreme toxicity in vitro of Bi(OH)₃ and α-Bi₂O₃ nanoparticles (NPs), obtained through a facile synthesis with an average single particle size of 6-10 nm, tested on malignant gliosarcoma 9L and MCF-7 human breast cancer cells. For both nanomaterials, clonogenic assays reveal a mortality of over 90% in 9L and MCF-7 cells for a concentration of 50 μg/mL after incubation for 24 h. Moreover, the NPs show a significant mortality of up to 60% in the malignant cells at the very low concentration of 6.25 μg/mL. In contrast, at the same concentration, the nanomaterials exhibit no noticeable mortality towards normal Madin-Darby canine kidney cells. The internalisation of the NPs was demonstrated using flow cytometry and confocal microscopy was used to investigate when the loss of cell viability starts. The NPs show a faster cell death in 9L cells compared with MCF-7 cells, demonstrated via the identification of apoptosis through increased sub G₁ levels after 24 h of NP incubation. Cleavage is identified as the main apoptotic nuclear morphology in 9L, which suggests the presence of reactive oxygen species.

Radiopaque UHMWPE sublaminar cables for spinal deformity correction: Preclinical mechanical and radiopacifier leaching assessment

Polymeric sublaminar cables have a number of advantages over metal cables in the field of spinal deformity surgery, with decreased risk of neurological injury and potential for higher correction forces as the two most predominant. However, currently available polymer cables are radiolucent, precluding postoperative radiological assessment of instrumentation stability and integrity. This study provides a preclinical assessment of a woven UHMWPE cable made with radiopaque UHMWPE fibers. Our primary goal was to determine if the addition of a radiopacifier negatively affects the mechanical properties of UHMWPE woven cables. Tensile mechanical properties were determined and compared to suitable controls. Radiopacity was evaluated and radiopacifier leaching was assessed in vitro and in vivo. Finally, in vivo bismuth organ content was quantified after a 24-week implantation period in sheep. Results show that the mechanical properties of woven UHMWPE cables were not deleteriously affected by the addition of homogenously dispersed bismuth oxide particles within each fiber. Limited amounts of bismuth oxide were released in vitro, well below the toxicological threshold. Tissue concentrations lower than generally accepted therapeutic dosages for use against gastrointestinal disorders, well below toxic levels, were discovered in vivo. These results substantiate controlled clinical introduction of these radiopaque UHMWPE cables. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 771-779, 2018.

The protective roles of some lichen species on colloidal bismuth subcitrate genotoxicity

Medicinal plants are increasingly being projected as suitable alternative source for the treatment of various diseases. However, toxic effects resulting from therapeutic bismuth compounds are still documented in animals and humans. This study described the genetic effects of five common lichen species and compared their activities on the genotoxicity induced by the colloidal bismuth subcitrate. After the application of colloidal bismuth subcitrate and lichen extracts, separate and together, human whole blood cultures were assessed by sister-chromatid exchange (SCE) and micronucleus tests. According to our results, the frequencies of SCE and micronucleus rate in peripheral lymphocytes were significantly increased by colloidal bismuth subcitrate (at dose 5 μg/mL) compared with controls. However, lichen extracts had no genotoxic effect. The order of anti-genotoxicity efficacy against colloidal bismuth subcitrate was Pseudevernia furfuracea, Dermotocarpon intestiniforme, Ramalina capitata, Parmelia pulla, respectively. However, Rhizoplaca melanophthalma did not show any effect against colloidal bismuth subcitrate genotoxicity. Present findings showed that the protective roles of lichens studied were dose related. In conclusion, this is the first study report describing the therapeutic potential of lichens against drug genotoxicity in human blood.

Complementary contrast media for metal artifact reduction in dual-energy computed tomography

Metal artifacts have been a problem associated with computed tomography (CT) since its introduction. Recent techniques to mitigate this problem have included utilization of high-energy (keV) virtual monochromatic spectral (VMS) images, produced via dual-energy CT (DECT). A problem with these high-keV images is that contrast enhancement provided by all commercially available contrast media is severely reduced. Contrast agents based on higher atomic number elements can maintain contrast at the higher energy levels where artifacts are reduced. This study evaluated three such candidate elements: bismuth, tantalum, and tungsten, as well as two conventional contrast elements: iodine and barium. A water-based phantom with vials containing these five elements in solution, as well as different artifact-producing metal structures, was scanned with a DECT scanner capable of rapid operating voltage switching. In the VMS datasets, substantial reductions in the contrast were observed for iodine and barium, which suffered from contrast reductions of 97% and 91%, respectively, at 140 versus 40 keV. In comparison under the same conditions, the candidate agents demonstrated contrast enhancement reductions of only 20%, 29%, and 32% for tungsten, tantalum, and bismuth, respectively. At 140 versus 40 keV, metal artifact severity was reduced by 57% to 85% depending on the phantom configuration.

CT Image Contrast of High-Z Elements: Phantom Imaging Studies and Clinical Implications

PURPOSE

To quantify the computed tomographic (CT) image contrast produced by potentially useful contrast material elements in clinically relevant imaging conditions.

MATERIALS AND METHODS

Equal mass concentrations (grams of active element per milliliter of solution) of seven radiodense elements, including iodine, barium, gadolinium, tantalum, ytterbium, gold, and bismuth, were formulated as compounds in aqueous solutions. The compounds were chosen such that the active element dominated the x-ray attenuation of the solution. The solutions were imaged within a modified 32-cm CT dose index phantom at 80, 100, 120, and 140 kVp at CT. To simulate larger body sizes, 0.2-, 0.5-, and 1.0-mm-thick copper filters were applied. CT image contrast was measured and corrected for measured concentrations and presence of chlorine in some compounds.

RESULTS

Each element tested provided higher image contrast than iodine at some tube potential levels. Over the range of tube potentials that are clinically practical for average-sized and larger adults-that is, 100 kVp and higher-barium, gadolinium, ytterbium, and tantalum provided consistently increased image contrast compared with iodine, respectively demonstrating 39%, 56%, 34%, and 24% increases at 100 kVp; 39%, 66%, 53%, and 46% increases at 120 kVp; and 40%, 72%, 65%, and 60% increases at 140 kVp, with no added x-ray filter.

CONCLUSION

The consistently high image contrast produced with 100-140 kVp by tantalum compared with bismuth and iodine at equal mass concentration suggests that tantalum could potentially be favorable for use as a clinical CT contrast agent.

Novel synthesis of thick wall coatings of titania supported Bi poisoned Pd catalysts and application in selective hydrogenation of acetylene alcohols in capillary microreactors

Catalysis in microreactors allows reactions to be performed in a very small volume, reducing the environmental problems and greatly intensifying the processes through easy pressure control and the elimination of heat- and mass-transfer limitations. In this study, we report a novel method for the controlled synthesis of micrometre-thick mesoporous TiO2 catalytic coatings on the walls of long channels (>1 m) of capillary microreactors in a single deposition step. The method uses elevated temperature and introduces a convenient control parameter of the deposition rate (displacement speed controlled by a stepper motor), which allows deposition from concentrated and viscous sols without channel clogging. A capillary microreactor wall-coated with titania supported Bi-poisoned Pd catalyst was obtained using the method and used for the semihydrogenation of 2-methyl-3-butyn-2-ol providing 93 ± 1.5% alkene yield for 100 h without deactivation. Although the coating method was applied only for TiO2 deposition, it is nonetheless suitable for the deposition of volatile sols.

Bismuth labeling for the CT assessment of local administration of magnetic nanoparticles

Many therapeutic applications of magnetic nanoparticles involve the local administration of nanometric iron oxide based materials as seeds for magnetothermia or drug carriers. A simple and widespread way of controlling the process using x-ray computed tomography (CT) scanners is desirable. The combination of iron and bismuth in one entity will increase the atenuation of x-rays, offering such a possibility. In order to check this possibility core-shell nanocrystals of iron oxide@bismuth oxide have been synthesized by an aqueous route and stabilized in water by polyethylene glycol (PEG), and we have evaluated their ability to generate contrast by CT and magnetic resonance imaging (MRI) to measure the radiopacity and proton relaxivities using phantoms. High-resolution scanning transmission electron microscopy (STEM) revealed that the material consists of a highly crystalline 8 nm core of maghemite and a 1 nm shell of bismuth atoms either isolated or clustered on the nanocrystal's surface. The comparison of μCT and MRI images of mice acquired in the presence of the contrast shows that when local accumulations of the magnetic nanoparticles take place, CT images are more superior in the localization of the magnetic nanoparticles than MRI images, which results in magnetic field inhomogeneity artifacts.

Review article: bismuth-based therapy for Helicobacter pylori eradication in children

BACKGROUND

Because of the decrease in the Helicobacter pylori eradication rate after standard triple therapy with a proton pump inhibitor and two antibiotics, bismuth-based therapy has recently been recommended as alternate first-line regimen in children.

AIM

To comprehensively review the clinical, pharmacologic and microbiologic properties of bismuth salts, and to summarise the evidence for the therapeutic efficacy of bismuth-based therapy for H. pylori eradication in children.

METHODS

Bibliographical searches were performed in MEDLINE. Results on the efficacy of bismuth-containing regimens on H. pylori eradication were combined using the inverse variance method.

RESULTS

Bismuth monotherapy showed a very low efficacy. Overall, the mean eradication rate with bismuth-based dual therapy was 68% (95% CI, 60-76%) (intention-to-treat analysis-ITT) and 73% (95% CI, 64-81%) (per protocol-PP). In case series, the overall percentages of children with successful eradication for triple therapy containing bismuth were 82% (95% CI, 76-88%) and 86% (95% CI, 80-92%) according to ITT and PP respectively. In comparative studies, H. pylori eradication rates ranged between 69% and 85% according to ITT and between 74% and 96% PP. Side effects included dark stools, urine discoloration, black tongue, burning tongue, and marked darkness of the gums.

CONCLUSIONS

The evidence in favour of bismuth compounds for treating infected children is still not clear. Well-designed, randomised, multi-centre studies of H. pylori eradication trials in children comparing bismuth-based triple therapy with the best available recommended first-line therapies are needed. The evidence obtained from audited case series that produce an eradication rate of >95% on PP analysis should also be considered.

The efficiacy of bismuth subnitrate against genotoxicity and oxidative stress induced by aluminum sulphate

Aluminum (Al) is commonly used in industrial processes and drugs and is thought to induce erythrocytes damage via activation of oxidative stress. Recently, bismuth (Bi)-containing drugs are used in the treatment of various diseases. However, uncertain effects of Bi in blood tissue may participate in the therapeutic efficacy of Bi compounds as related to metals. Hence, this study aimed to determine the roles on human blood cells of the various concentrations of aluminum sulphate (Al2 (SO4)3) and bismuth subnitrate (BSN), separate and together. With this aim, oxidative status was assessed on erythrocytes by measuring following oxidative stress markers: reduced glutathione (GSH), superoxide dismutase (SOD), glucose-6-phosphate dehydrogenase (G-6-PDH) and catalase (CAT). Two chemicals were tested for their ability to induce cytogenetic change in human lymphocytes using assays for chromosome aberrations (CAs) and sister chromatid exchanges (SCEs). Our results showed that high dose of Al2(SO4)3 (20 µg/mL) caused oxidative stress and increased CA and SCE frequencies. Whereas, BSN doses did not change CA and SCE rates. Moreover, it led to changes of antioxidant capacity at different concentrations. After concomitant treatment with Al2(SO 4)3 and BSN, the effects of BSN doses were different on enzyme activities and decreased the genotoxic damage. However, the high dose of BSN and Al2(SO4)3 was shown to enhance the frequencies of CAs and SCEs in a synergistic manner. In conclusion, BSN could be effective in the protection against the blood toxicity of Al 2(SO4)3.

Effects of bismuth contamination on the growth and activity of soil microorganisms using thiols as model compounds

The present study was undertaken to obtain information about the effects of Bi contamination on soil microbial growth and activity using a series of Bi complexes with thiol compounds, including mercaptoethanol, thioglycerol, mercaptoethylamine, thioglycolic acid, thiomallic acid, reduced glutathione, 2-mercaptopropionic acid, and L-cysteine. We found that Bi complexes with mercaptoethanol, thioglycerol, and mercaptoethylamine, all of which showed lipophilicity, markedly inhibited bacterial growth in 1/10 TSB liquid media in both Eutric Cambisol (brown forest soil) and Eutric Fluvisol (brown lowland soil), with relative CFU of less than 2% at 50 micro M Bi and 6% at 25 micro M Bi. However, none of the Bi-thiols, including Highly lipophilic complexes, at 200 micro M Bi in rosebengal agar medium inhibited fungal growth, possibly because fungi have a metabolic system that protects against Bi uptake or detoxifies Bi compounds. When soil was contaminated experimentally with Bi-thiol, these complexes suppressed soil dehydrogenase activity, particularly in brown forest soil, which contains large amounts of easily decomposable organic matter. These results indicate that the effects of Bi on soil microbes may depend on mutual reactions with organic matter in the environment.

Human biokinetics of injected bismuth-207

A healthy male volunteer received an intravenous injection of 207Bi as citrate. Levels of the tracer in blood and in excretion samples, and its retention and distribution within the body, were investigated by appropriate radioactivity measurements. Levels in blood fell very rapidly, with only 1% of the injection remaining at 7 h and only ca. 0.1% at 18 days. There was rapid initial excretion, with 55% lost during the first 47 h, principally in urine; however, longer-term losses were much slower and 0.6% remained in the body at 924 days, when the contemporary rate of loss implied a half-life of 1.9 years. Integration of the retention pattern suggested that steady exposure to bismuth compounds could lead ultimately to a body content of approximately 24 times the daily systemic uptake. The largest organ deposit was in the liver, which after 3 days contained ca. 60% of the contemporary whole body content, consistent with reports of hepatotoxicity. These findings differ markedly from the metabolic model for bismuth proposed by the International Commission on Radiological Protection, which envisages a terminal half-life in the body of only 5 days and kidney as the site of highest deposition.

GR122311X (ranitidine bismuth citrate), a new drug for the treatment of duodenal ulcer

BACKGROUND

Ranitidine bismuth citrate (GR122311X) is a new drug which offers potential benefits in healing duodenal ulcers and prevention of relapse.

METHODS

This randomized, multi-centre double-blind study of 1620 patients compared the effect of 4 weeks of treatment with GR122311X 200 mg b.d. (n = 401), 400 mg b.d. (n = 404) or 800 mg b.d. (n = 404) or ranitidine hydrochloride 150 mg b.d. (n = 411) on the rates of duodenal ulcer healing and of overall success (ulcers healed and remaining ulcer free in the 24-week follow-up phase).

RESULTS

All four treatments were equally effective at ulcer healing (79%, 85%, 84% and 81% of patients, respectively). GR122311X 400 mg b.d. (38%) and 800 mg b.d. (37%) were significantly more effective than ranitidine hydrochloride 150 mg b.d. (32%) with respect to overall success (P = 0.050 and P = 0.030, respectively) but there was no difference with GR122311X 200 mg b.d. (31%). GR122311X caused effective, dose-related suppression of H. pylori (47%, 61% and 74%); H. pylori eradication rates were 18%, 21% and 22%. GR122311X was safe and well tolerated, with an adverse event profile similar to that of ranitidine hydrochloride 150 mg b.d. Median week 4 trough plasma bismuth levels were 1.3 ng/mL, 2.3 ng/mL and 3.3 ng/mL with GR122311X 200 mg b.d., 400 mg b.d. and 800 mg b.d. respectively. No individual plasma bismuth concentrations were of clinical concern.

CONCLUSIONS

GR122311X is a safe and effective ulcer healing drug, and provides a platform on which anti-H. pylori therapy can be based.

Absorption of bismuth from several bismuth compounds during in vivo perfusion of rat small intestine

Evaluation of the amount of bismuth (Bi) absorbed from the gastrointestinal tract is important for assessment of the possible risks associated with the use of Bi compounds in the treatment of gastrointestinal disorders. We compared the absorption of Bi from media containing the equivalent of 1 g of elemental Bi from either Bi subnitrate (BSN), Bi subsalicylate (BSS), colloidal Bi subcitrate (CBS), Bi chloride (BiCl3), or Bi citrate (BCit) by an in vivo perfusion system of rat small intestine. The intestinal absorption was < 1% for all compounds, but higher from BCit and CBS than from BSN, BSS, and BiCl3. The dose dependency of Bi absorption from both CBS and BiCl3 in citrate buffer showed a nonlinear relationship between the concentration of Bi in perfusate and the concentration of Bi in blood after 60 min.

Is there a place for antacids in the treatment of Helicobacter pylori infection?

Two pilot studies were performed to determine whether aluminium-containing antacids may have a place in the treatment of Helicobacter pylori infection. The urease activity of H. pylori is cytopathic to gastric epithelium, and inhibition of this enzyme may have therapeutic potential. In the first study 24 subjects, 12 of which were infected with H. pylori, were given 1 tablet of chewable aluminium hydroxide-containing antacids 10 min before a 14C-urea breath test. Gastric urease activity was suppressed by 33.3% (p = 0.02) in the H. pylori-positive subjects (none became negative) within 40 min after administration of the tablet. Gastric H. pylori infection can be effectively eradicated by triple regimens containing bismuth salts, tetracycline, and metronidazole. Owing to adverse effects of this treatment and concern for possible neurotoxicity of bismuth, a bismuth substitute is warranted. Hence, in the second study, 20 subjects infected with H. pylori were treated with 1 antacid tablet 4 times daily between meals, plus 500 mg oxytetracycline and 200 mg metronidazole 4 times daily with meals for 2 weeks. Individual H. pylori status was assessed by the 14C-urea breath test. Four weeks after cessation of treatment, H. pylori was eradicated in 45% (9 of 20) of the subjects (95% confidence interval, 23.1-68.5%). Thirty per cent (6 of 20) observed one or more adverse effect regarded as moderate or severe, of which loose stools and headache were the most common.(ABSTRACT TRUNCATED AT 250 WORDS)