Pharmacokinetics and toxicity of bismuth compounds

Renal epithelial gene expression profile and bismuth-induced resistance against cisplatin nephrotoxicity

Nephrotoxicity is the most important dose-limiting factor in cisplatin based anti-neoplastic treatment. Pretreatment with bismuth salts, used as pharmaceuticals to treat gastric disorders, has been demonstrated to reduce cisplatin-induced renal cell death in clinical settings and during in vivo and in vitro animal experiments. To investigate the genomic basis of this renoprotective effect, we exposed NRK-52E cells, a cell line of rat proximal tubular epithelial origin, to 33 mM Bi3for 12 hours, which made them resistant to cisplatin-induced apoptosis. Differentially expressed genes in treated and untreated NRK-52E cells were detected by subtraction PCR and microarray techniques. Genes found to be down regulated (0.17/0.31-times) were cytochrome c oxidase subunit I, BAR (an apoptosis regulator), heat-shock protein 70-like protein, and three proteins belonging to the translation machinery (ribosomal proteins S7 and L17, and S1, a member of the elongation factor 1-alpha family). The only up-regulated gene was glutathione Stransferase subunit 3A (1.89-times). Guided by the expression levels of these genes, it may be possible to improve renoprotective treatments during anti-neoplastic therapies.

Different bismuth-based therapies for eradicating Helicobacter pylori: Randomized clinical trial of efficacy and safety

BACKGROUND AND OBJECTIVE

Bismuth salts are used for treating dyspepsia, and they exert antibacterial effects on Helicobacter pylori. This study aimed to compare the efficacy and safety of three bismuth-containing combination regimens for H. pylori eradication in a Turkish population.

METHODS

In this single-center study, 149 patients, who were diagnosed with H. pylori infection with urea breath test and histopathological examination, were randomized to receive the following therapies for 14 days: (1) bismuth-containing clarithromycin-based triple therapy (CBS-LAC), (2) bismuth-containing levofloxacin-based triple therapy (CBS-LAL), and (3) bismuth-containing quadruple therapy (BCQT). Eradication rates were evaluated six weeks after the treatment by performing intention to treat (ITT) and per protocol (PP) analyses. In addition, data on side effect profiles and patient compliance were collected.

RESULTS

PP and ITT analyses showed that eradication rates were 86% and 81.1%, respectively, with BCQT; 68.3% and 66.7%, respectively, with CBS-LAL therapy; and 65.3% and 59.3%, respectively, with CBS-LAC therapy. Eradication rates obtained using PP and ITT analyses were statistically significant for all the regimens.

CONCLUSION

Addition of bismuth to standard triple and levofloxacin-based regimen did not show an acceptable increase in eradication rates. Therefore, BCQT may be preferred for the first-line treatment of H. pylori infection.

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.

Determination of bismuth in environmental samples by slurry sampling graphite furnace atomic absorption spectrometry using combined chemical modifiers

Slurry sampling graphite furnace atomic absorption spectrometry technique was applied for the determination of Bi in environmental samples. The study focused on the effect of Zr, Ti, Nb and W carbides, as permanent modifiers, on the Bi signal. Because of its highest thermal and chemical stability and ability to substantially increase Bi signal, NbC was chosen as the most effective modifier. The temperature programme applied for Bi determination was optimized based on the pyrolysis and atomization curves obtained for slurries prepared from certified reference materials (CRMs) of the soil and sediments. To overcome interferences caused by sulfur compounds, Ba(NO₃)₂ was used as a chemical modifier. Calibration was performed using the aqueous standard solutions. The analysis of the CRMs confirmed the reliability of the proposed analytical method. The characteristic mass for Bi was determined to be 16 pg with the detection limit of 50 ng/g for the optimized procedure at the 5% (w/v) slurry concentration.

Dual-modality, fluorescent, PLGA encapsulated bismuth nanoparticles for molecular and cellular fluorescence imaging and computed tomography

Reports of molecular and cellular imaging using computed tomography (CT) are rapidly increasing. Many of these reports use gold nanoparticles. Bismuth has similar CT contrast properties to gold while being approximately 1000-fold less expensive. Herein we report the design, fabrication, characterization, and CT and fluorescence imaging properties of a novel, dual modality, fluorescent, polymer encapsulated bismuth nanoparticle construct for computed tomography and fluorescence imaging. We also report on cellular internalization and preliminary in vitro and in vivo toxicity effects of these constructs. 40 nm bismuth(0) nanocrystals were synthesized and encapsulated within 120 nm Poly(dl-lactic-co-glycolic acid) (PLGA) nanoparticles by oil-in-water emulsion methodologies. Coumarin-6 was co-encapsulated to impart fluorescence. High encapsulation efficiency was achieved ∼70% bismuth w/w. Particles were shown to internalize within cells following incubation in culture. Bismuth nanocrystals and PLGA encapsulated bismuth nanoparticles exhibited >90% and >70% degradation, respectively, within 24 hours in acidic, lysosomal environment mimicking media and both remained nearly 100% stable in cytosolic/extracellular fluid mimicking media. μCT and clinical CT imaging was performed at multiple X-ray tube voltages to measure concentration dependent attenuation rates as well as to establish the ability to detect the nanoparticles in an ex vivo biological sample. Dual fluorescence and CT imaging is demonstrated as well. In vivo toxicity studies in rats revealed neither clinically apparent side effects nor major alterations in serum chemistry and hematology parameters. Calculations on minimal detection requirements for in vivo targeted imaging using these nanoparticles are presented. Indeed, our results indicate that these nanoparticles may serve as a platform for sensitive and specific targeted molecular CT and fluorescence imaging.

Renal pigmentation due to chronic bismuth administration in a rhesus macaque (Macaca mulatta)

Renal pigmentation due to the administration of exogenous compounds is an uncommon finding in most species. This report describes renal pigmentation and intranuclear inclusions of the proximal convoluted tubules due to chronic bismuth administration in a rhesus macaque. An 11-year-old Indian-origin rhesus macaque with a medical history of chronic intermittent vomiting had been treated with bismuth subsalicylate, famotidine, and omeprazole singly or in combination over the course of 8 years. At necropsy, the renal cortices were diffusely dark green to black. Light and electron microscopy revealed intranuclear inclusions within the majority of renal proximal tubular epithelial cells. These inclusions appeared magenta to brown when stained with hematoxylin and eosin and were negative by the Ziehl-Neelsen acid-fast stain. Elemental analysis performed on frozen kidney measured bismuth levels to be markedly elevated at 110.6 ppm, approximately 500 to 1000 times acceptable limits. To our knowledge, this is the first report of renal bismuth deposition in a rhesus macaque resulting in renal pigmentation and intranuclear inclusions.

The status of radioimmunotherapy in CD20+ non-Hodgkin's lymphoma

Rituximab, the CD20-directed antibody, has become a standard component of treatment regimens for patients with B cell non-Hodgkin's lymphoma (NHL). The use of rituximab has resulted in greatly improved response and survival rates with less toxicity relative to standard chemotherapeutic regimes. However, relapse and recurrence is common, particularly in indolent varieties which remain incurable, requiring alternate therapeutic options. The subsequent coupling of β-emitting isotopes such as (131)I and (90)Y to anti-CD20 monoclonal antibodies (mAbs), including rituximab, has been steadily growing over the last decade and demonstrates even greater therapeutic efficacy with more durable responses. (177)Lutetium-labelled rituximab offers a number of convenient advantages over (131)I and (90)Y anti-CD20 mAbs for treatment of NHL, and a number of alpha-emitting isotopes lie at the frontier of consolidation therapy for residual, micrometastatic disease.

Crofelemer, a novel agent for treatment of non-infectious diarrhea in HIV-infected persons

Crofelemer is the first US FDA-approved drug for symptomatic relief in HIV-infected persons on antiretroviral therapy (ART) who have non-infectious diarrhea. With the availability of ART, there is increased survival and decrease in gastrointestinal opportunistic infections. However, diarrhea secondary to ART and HIV enteropathy is common in HIV-infected persons. Crofelemer is manufactured from the red latex sap of the Croton lechleri tree in South America. It has a unique mechanism leading to inhibition of chloride ion secretion by blocking chloride channels in the gastrointestinal lumen. This reduces efflux of sodium and water, which in turn reduces the frequency and consistency of diarrhea. Crofelemer is well tolerated due to minimal systemic absorption and has a good safety profile. The availability of crofelemer will likely have a positive impact on the quality of life in HIV-infected persons and also increase compliance to ART.

Helicobacter pylori eradication with ecabet sodium, omeprazole, amoxicillin, and clarithromycin versus bismuth, omeprazole, amoxicillin, and clarithromycin quadruple therapy: a randomized, open-label, phase IV trial

BACKGROUND

Helicobacter pylori infection is a substantial public health problem and plays etiological role in the pathogenesis of many gastroduodenal disorders. The addition of ecabet sodium is proven to improve the efficacy of the standard triple therapy. Our aim was to assess the efficacy and safety of ecabet sodium-containing quadruple therapy versus 10-day bismuth-containing quadruple therapy for H. pylori eradication.

MATERIALS AND METHODS

We did a randomized, open-label, phase IV trial in four cities (eight sites) in China, comparing the efficacy and safety of 10-days ecabet sodium-containing versus bismuth-containing quadruple therapy in adults with H. pylori infection. Eligible patients were randomly assigned treatment and monitored H. pylori eradication by negative [13C]/[14C] urea breath test 28 days after the treatment as the primary outcome. Symptoms improvement and side effects were the secondary outcome.

RESULTS

A total of 311 H. pylori-positive subjects were enrolled: 155 were assigned ecabet sodium quadruple therapy and 156 bismuth quadruple therapy. The eradication rates with ecabet sodium-containing and bismuth-containing quadruple regimens were 68.4% (106/155) and 68.0% (106/156) p = .9339 intention-to-treat (ITT) and 75.4% (104/138) and 77.0% (104/135) p = .7453 per-protocol (PP), respectively. The eradication rates for the ecabet sodium quadruple regimen differed significantly between cities (e.g., 81.2% ITT and 89.6% PP in Shanghai and 50% ITT and 53.5% PP in Xi'an). The symptom improvements and safety profiles were also similar for both treatments.

CONCLUSIONS

Neither 10-day Ecabet sodium-containing quadruple therapy or 10-day bismuth-containing quadruple therapy can be recommended as empiric therapy in cities with high antibiotic resistance rate of China.

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.

Helicobacter pylori eradication with a capsule containing bismuth subcitrate potassium, metronidazole, and tetracycline given with omeprazole versus clarithromycin-based triple therapy: a randomised, open-label, non-inferiority, phase 3 trial

BACKGROUND

Helicobacter pylori is associated with benign and malignant diseases of the upper gastrointestinal tract, and increasing antibiotic resistance has made alternative treatments necessary. Our aim was to assess the efficacy and safety of a new, single-capsule treatment versus the gold standard for H pylori eradication.

METHODS

We did a randomised, open-label, non-inferiority, phase 3 trial in 39 sites in Europe, comparing the efficacy and safety of 10 days of quadruple therapy with omeprazole plus a single three-in-one capsule containing bismuth subcitrate potassium, metronidazole, and tetracycline (quadruple therapy) versus 7 days of omeprazole, amoxicillin, and clarithromycin (standard therapy) in adults with recorded H pylori infection. Patients were randomly assigned treatment according to a predetermined list independently generated by Quintiles Canada (Ville St-Laurent, QC, Canada). Our study was designed as a non-inferiority trial but was powered to detect superiority. Our primary outcome was H pylori eradication, established by two negative (13)C urea breath tests at a minimum of 28 and 56 days after the end of treatment. Our assessment for non-inferiority was in the per-protocol population, with subsequent assessment for superiority in the intention-to-treat population (ie, all participants randomly assigned treatment). This study is registered with ClinicalTrials.gov, number NCT00669955.

FINDINGS

12 participants were lost to follow-up and 101 were excluded from the per-protocol analysis. In the per-protocol population (n=339), the lower bound of the CI for treatment with quadruple therapy was greater than the pre-established non-inferiority margin of -10% (95% CI 15·1-32·3; p<0·0001). In the intention-to-treat population (n=440), eradication rates were 80% (174 of 218 participants) in the quadruple therapy group versus 55% (123 of 222) in the standard therapy group (p<0·0001). Safety profiles for both treatments were similar; main adverse events were gastrointestinal and CNS disorders.

INTERPRETATION

Quadruple therapy should be considered for first-line treatment in view of the rising prevalence of clarithromycin-resistant H pylori, especially since quadruple therapy provides superior eradication with similar safety and tolerability to standard therapy.

FUNDING

Axcan Pharma Inc.

Renal uptake of bismuth-213 and its contribution to kidney radiation dose following administration of actinium-225-labeled antibody

Clinical therapeutic studies using (225)Ac-labeled antibodies have begun. Of major concern is renal toxicity that may result from the three alpha-emitting progeny generated following the decay of (225)Ac. The purpose of this study was to determine the amount of (225)Ac and non-equilibrium progeny in the mouse kidney after the injection of (225)Ac-huM195 antibody and examine the dosimetric consequences. Groups of mice were sacrificed at 24, 96 and 144 h after injection with (225)Ac-huM195 antibody and kidneys excised. One kidney was used for gamma ray spectroscopic measurements by a high-purity germanium (HPGe) detector. The second kidney was used to generate frozen tissue sections which were examined by digital autoradiography (DAR). Two measurements were performed on each kidney specimen: (1) immediately post-resection and (2) after sufficient time for any non-equilibrium excess (213)Bi to decay completely. Comparison of these measurements enabled estimation of the amount of excess (213)Bi reaching the kidney (γ-ray spectroscopy) and its sub-regional distribution (DAR). The average absorbed dose to whole kidney, determined by spectroscopy, was 0.77 (SD 0.21) Gy kBq(-1), of which 0.46 (SD 0.16) Gy kBq(-1) (i.e. 60%) was due to non-equilibrium excess (213)Bi. The relative contributions to renal cortex and medulla were determined by DAR. The estimated dose to the cortex from non-equilibrium excess (213)Bi (0.31 (SD 0.11) Gy kBq(-1)) represented ∼46% of the total. For the medulla the dose contribution from excess (213)Bi (0.81 (SD 0.28) Gy kBq(-1)) was ∼80% of the total. Based on these estimates, for human patients we project a kidney-absorbed dose of 0.28 Gy MBq(-1) following administration of (225)Ac-huM195 with non-equilibrium excess (213)Bi responsible for approximately 60% of the total. Methods to reduce renal accumulation of radioactive progeny appear to be necessary for the success of (225)Ac radioimmunotherapy.

Methylated Metal(loid) Species in Humans

While the metal(loid)s arsenic, bismuth, and selenium (probably also tellurium) have been shown to be enzymatically methylated in the human body, this has not yet been demonstrated for antimony, cadmium, germanium, indium, lead, mercury, thallium, and tin, although the latter elements can be biomethylated in the environment. Methylated metal(loid)s exhibit increased mobility, thus leading to a more efficient metal(loid) transport within the body and, in particular, opening chances for passing membrane barriers (blood-brain barrier, placental barrier). As a consequence human health may be affected. In this review, relevant data from the literature are compiled, and are discussed with respect to the evaluation of assumed and proven health effects caused by alkylated metal(loid) species.

Pylera for the eradication of Helicobacter pylori infection

An ideal antibiotic regimen for Helicobacter pylori should achieve eradication rates of approximately 90%. Current 7-day triple therapy is successful in about two-thirds of patients. A novel treatment is required to achieve higher eradication with minimal induction of bacterial resistance. The aim of this article is to evaluate the safety and efficacy of a single triple capsule (Pylera) containing bismuth, metronidazole and tetracycline, given with omeprazole for the eradication of H. pylori infection. Extensive literature searches were conducted using PubMed data from 1982 to 2007. This search included headings of H. pylori, bismuth and eradication therapy. The triple capsule Pylera, when given with omeprazole, achieved eradication rates ranging between 84 and 97%. Eradication rates were similar for clarithromycin- and metronidazole-resistant strains. Eradication rates with an omeprazole, bismuth, metronidazole and tetracycline regimen appeared comparable for metronidazole-resistant and -sensitive strains. This effect is not seen with the use of triple therapy in cases of clarithromycin resistance. Clinical trials did not report any serious side effects from bismuth-based regimens and compliance was similar to standard triple therapy. Bismuth-based triple therapy using Pylera is a simplified, effective and well-tolerated regimen achieving cure rates of above 90%.

Chelation of bismuth by combining desferrioxamine and deferiprone in rats

Consumption and production of bismuth compounds are increasing, however, a little information on the toxic effect and also the effective method in removal of bismuth compounds are available. The present research aimed to characterize the potential efficiency of two chelators after bismuth administration for 55 days following two dose levels of 20 and 40 mg/kg body weight daily to male rats. However, we found abnormalities after bismuth administration in clinical signs, such as body weight, kidneys and liver damages, a black line on gums and skin reactions. Furthermore, the hypothesis that the two chelators might be more efficient as combined therapy than as single therapy in removing bismuth from the body was considered. Along this line, two known chelators deferiprone (1, 2-dimethy1-3-hydroxypyride-4-one, L1) and desferrioxamine (DFO) were chosen and tested in the acute rat model. Chelators were given orally (L1) or intraperitoneally (DFO) as a single or combined therapy for the period of a week. Doses of L1 and DFO were 110 mg/kg body weight in experiments. Bismuth and iron concentrations in various tissues were determined by graphite furnace and flame atomic absorption spectrometry, respectively. The combined chelation therapy results show that DFO and L1 are able to remove bismuth ions from the body, whereas iron concentration returned to the normal level and symptoms are also decreased. DFO was more effective than L1 in reducing bismuth concentration in tissues. The efficiency of DFO + L1 is more than DFO or L1 in removing bismuth from organs. Our results are indicative that the design procedure might be useful for preliminary in-vivo testing of the efficiency of chelating agents. Results of combined chelators’ treatment should be confirmed in a different experimental model before extrapolation to other systems. This testing procedure of course does not provide all the relevant answers for efficiency of chelating agents in bismuth toxicity.

Bioinorganic chemistry of bismuth and antimony: target sites of metallodrugs

The biocoordination chemistry of antimony and bismuth has been extensively investigated due to the historical use of these metals in medicine. Structures of bismuth antiulcer agents and interactions of Bi3+ with proteins and enzymes, such as transferrin and lactoferrin, the histidine-rich protein Hpn, and urease, have been characterized. Sb5+ is a prodrug and is bioreduced or activated to its active form Sb3+ intracellularly. Antimony binds to biomolecules, such as glutathione, trypanothione, and nucleotides, and forms binary and ternary complexes, which may allow it to be trafficked in cells. These studies have improved our understanding of the mechanism of action of bismuth and antimony drugs, which in turn allows the future design of drugs.

Is there a need to re-examine the approval of bismuth shotshell as a non-toxic alternative to lead based on the precautionary principle?

In 1997, the Canadian Wildlife Service (CWS) approved bismuth shotshell as an alternative to lead. We assessed whether there is a need to re-examine the toxicity of bismuth issue using the initial CWS toxicity guideline criteria. Review of the literature suggests that in the context of the precautionary principle, a re-examination of the approval of bismuth shotshell should be undertaken based on animal health issues, associated deficiencies in the analytical data used in the original assessment, and to a lesser extent, human health concerns.

Pharmacokinetics and bioequivalence of ranitidine and bismuth derived from two compound preparations

AIM: To evaluate the bioequivalence of ranitidine and bismuth derived from two compound preparations.

METHODS: The bioavailability was measured in 20 healthy male Chinese volunteers following a single oral dose (equivalent to 200 mg of ranitidine and 220 mg of bismuth) of the test or reference products in the fasting state. Then blood samples were collected for 24 h. Plasma concentrations of ranitidine and bismuth were analyzed by high-performance liquid chromatography and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. The non-compartmental method was used for pharmacokinetic analysis. Log-transformed C_max, AUC_(0-t) and AUC_(0-∞) were tested for bioequivalence using ANOVA and Schuirmann two-one sided t-test. T_max was analyzed by Wilcoxon’s test.

RESULTS: Various pharmacokinetic parameters of ranitidine derived from the two compound preparations, including C_max, AUC_(0-t), AUC_(0-∞), T_max and T_1/2, were nearly consistent with previous observations. These parameters derived from test and reference drug were as follows: C_max (0.67 ± 0.21 vs 0.68 ± 0.22 mg/L), AUC_(0-t) (3.1 ± 0.6 vs 3.0 ± 0.7 mg/L per hour), AUC_(0-∞) (3.3 ± 0.6 vs 3.2 ± 0.8 mg/L per hour), T_max (2.3 ± 0.9 vs 2.1 ± 0.9 h) and T_1/2 (2.8 ± 0.3 vs 3.1 ± 0.4 h). In addition, double-peak absorption profiles of ranitidine were found in some Chinese volunteers. For bismuth, those parameters derived from test and reference drug were as follows: C_max (11.80 ± 7.36 vs 11.40 ± 6.55 μg/L), AUC_(0-t) (46.65 ± 16.97 vs 47.03 ± 21.49 μg/L per hour), T_max (0.50 ± 0.20 vs 0.50 ± 0.20 h) and T_1/2 (10.2 ± 2.3 vs 13.0 ± 6.9 h). Ninety percent of confidence intervals for the test/reference ratio of C_max, AUC_(0-t) and AUC_(0-) derived from both ranitidine and bismuth were found within the bioequivalence acceptable range of 80%-125%. No significant difference was found in T_max derived from both ranitidine and bismuth.

CONCLUSION: The two compound preparations are bioequivalent and may be prescribed interchangeably.

Acute renal failure after overdose of colloidal bismuth subcitrate

Bismuth salts are widely used to treat peptic ulcers. Acute toxicity with colloidal bismuth subcitrate overdose causes nephrotoxicity. There have been numerous reports of encephalopathy after long-term consumption of bismuth salts, but only a few cases of nephrotoxicity (adult and pediatric) have been documented to date. This report presents a case of acute renal failure due to colloidal bismuth subcitrate overdose in adolescent. A 16-year-old girl presented with complaints of nausea, vomiting, and facial paresthesia. Ten days earlier she had tried to commit suicide by taking 60 tablets of De-nol (colloidal bismuth subcitrate 18 g). The physical examination findings on admission indicated minimal fluid overload but no signs of encephalopathy. Laboratory tests on admission showed blood urea nitrogen 102 mg/dl, serum creatinine 19.9 mg/dl, and serum bismuth level 495 microg/l. The patient was started on appropriate fluid therapy and penicillamine as a chelating agent and then began hemodialysis on alternate days. The patient's renal function gradually returned to normal over 9 weeks and by 64 days after the overdose her serum bismuth level had fallen to almost half the level detected 2 days after admission. The patient made a complete recovery. The case demonstrates that acute renal failure can develop as a manifestation of acute toxicity from colloidal bismuth ingestion, and that the prognosis may be favorable if the patient receives appropriate supportive treatment and dialysis.

Efforts to control the errant products of a targeted in vivo generator

Alpha-particle immunotherapy by targeted alpha-emitters or alpha-emitting isotope generators is a novel form of extraordinarily potent cancer therapy. A major impediment to the clinical use of targeted actinium-225 (225Ac) in vivo generators may be the radiotoxicity of the systemically released daughter radionuclides. The daughters, especially bismuth-213 (213Bi), tend to accumulate in the kidneys. We tested the efficacy of various pharmacologic agents and the effect of tumor burden in altering the pharmacokinetics of the 225Ac daughters to modify their renal uptake. Pharmacologic treatments in animals were started before i.v. administration of the HuM195-225Ac generator. 225Ac, francium-221 (221Fr), and 213Bi biodistributions were calculated in each animal at different time points after 225Ac generator injection. Oral metal chelation with 2,3-dimercapto-1-propanesulfonic acid (DMPS) or meso-2,3-dimercaptosuccinic acid (DMSA) caused a significant reduction (P < 0.0001) in the renal 213Bi uptake; however, DMPS was more effective than DMSA (P < 0.001). The results with DMPS were also confirmed in a monkey model. The renal 213Bi and 221Fr activities were significantly reduced by furosemide and chlorothiazide treatment (P < 0.0001). The effect on renal 213Bi activity was further enhanced by the combination of DMPS with either chlorothiazide or furosemide (P < 0.0001). Competitive antagonism by bismuth subnitrate moderately reduced the renal uptake of 213Bi. The presence of a higher target-tumor burden significantly prevented the renal 213Bi accumulation (P = 0.003), which was further reduced by DMPS treatment (P < 0.0001). Metal chelation, diuresis with furosemide or chlorothiazide, and competitive metal blockade may be used as adjuvant therapies to modify the renal accumulation of 225Ac daughters.

Transferrin: structure, function and potential therapeutic actions

There are many proteins that can multi-task. Transferrin, widely known as an iron-binding protein, is one such example of a multi-tasking protein. In this review, the multiple biological actions of transferrin, including its growth and cytoprotective activities, are discussed with the view of highlighting the potential therapeutic applications of this protein.

Renal tubulointerstitial changes after internal irradiation with alpha-particle-emitting actinium daughters

The effect of external gamma irradiation on the kidneys is well described. However, the mechanisms of radiation nephropathy as a consequence of targeted radionuclide therapies are poorly understood. The functional and morphologic changes were studied chronologically (from 10 to 40 wk) in mouse kidneys after injection with an actinium-225 (225Ac) nanogenerator, a molecular-sized, antibody-targeted, in vivo generator of alpha-particle-emitting elements. Renal irradiation from free, radioactive daughters of 225Ac led to time-dependent reduction in renal function manifesting as increase in blood urea nitrogen. The histopathologic changes corresponded with the decline in renal function. Glomerular, tubular, and endothelial cell nuclear pleomorphism and focal tubular cell injury, lysis, and karyorrhexis were observed as early as 10 wk. Progressive thinning of the cortex as a result of widespread tubulolysis, collapsed tubules, glomerular crowding, decrease in glomerular cellularity, interstitial inflammation, and an elevated juxtaglomerular cell count were noted at 20 to 30 wk after treatment. By 35 to 40 wk, regeneration of simplified tubules with tubular atrophy and loss with focal, mild interstitial fibrosis had occurred. A lower juxtaglomerular cell count with focal cytoplasmic vacuolization, suggesting increased degranulation, was also observed in this period. A focal increase in tubular and interstitial cell TGF-beta1 expression starting at 20 wk, peaking at 25 wk, and later declining in intensity with mild increase in the extracellular matrix deposition was noticed. These findings suggest that internally delivered alpha-particle irradiation-induced loss of tubular epithelial cells triggers a chain of adaptive changes that result in progressive renal parenchymal damage accompanied by a loss of renal function. These findings are dissimilar to those seen after gamma or beta irradiation of kidneys.

Determining the background levels of bismuth in tissues of wild game birds: a first step in addressing the environmental consequences of using bismuth shotshells

Bismuth shotshells have been approved as a "nontoxic" alternative to lead in North America. Approval was based on a limited number of studies; even background levels of bismuth in wildfowl were unknown. We report on the concentration of bismuth (and lead) in muscle and liver tissues of wildfowl (Anas platyrhynchos, Anas acuta, Anas crecca, Branta canadensis, Chen caerulescens) harvested with lead shotshell. Average liver-bismuth levels detected in the present study (e.g., teal, 0.05 microg/g dw; mallard, 0.09 microg/g dw) suggest analytical error in other studies examining the effects of bismuth in birds. Significant positive relationships between bismuth- and lead-tissue levels for muscle when all species were combined (and for B. canadensis and C. caerulescens separately) can be explained by noting that bismuth is a contaminant of lead. Thus, more research is recommended to confirm the appropriateness of bismuth as a "nontoxic" shot alternative.

Influence of omeprazole on bioavailability of bismuth following administration of a triple capsule of bismuth biskalcitrate, metronidazole, and tetracycline

The objective of this study was to determine the impact of omeprazole on bismuth (Bi) bioavailability when given in a three-in-one capsule containing bismuth biskalcitrate, metronidazole, and tetracycline. Thirty-four healthy volunteers were randomly assigned to receive three capsules (each containing bismuth biskalcitrate 140 mg + metronidazole 125 mg + tetracycline 125 mg) qid alone x 6 days or the same treatment + omeprazole (OM) 20 mg bid. Blood was drawn at intervals for 24 hours after the last dose. After the last dose, mean (CV) C(min) for plasma bismuth was 2882 pg/mL (36%) and 1195 pg/mL (23%) (p< 0.001), with and without OM, respectively. Mean (CV) C(max) was 25493 pg/mL (69%) and 8061 pg/mL (28%) (p < 0.001) with and without OM, respectively. AUC(0-24) increased by 2.9 in presence of OM (p < 0.001). Adverse events in both groups were usually mild and of a gastrointestinal nature, and all had resolved by the end of the trial. This study confirms an interaction between Bi biskalcitrate and OM. Risk of Bi toxicity, seen after long-term use of Bi compounds, is minimal here because plasma levels of Bi remained well below the toxic levels of 50 microg/L, and the treatment period with this triple capsule + OM is only 10 days, a substantially lower number of days compared to that which might produce Bi toxicity.

Environmental distribution, analysis, and toxicity of organometal(loid) compounds

The biochemical modification of the metals and metalloids mercury, tin, arsenic, antimony, bismuth, selenium, and tellurium via formation of volatile metal hydrides and alkylated species (volatile and involatile) performs a fundamental role in determining the environmental processing of these elements. In most instances, the formation of such species increases the environmental mobility of the element, and can result in bioaccumulation in lipophilic environments. While inorganic forms of most of these compounds are well characterized (e.g., arsenic, mercury) and some of them exhibit low toxicity (e.g., tin, bismuth), the more lipid-soluble organometals can be highly toxic. Methylmercury poisoning (e.g., Minamata disease) and tumor development in rats after exposure to dimethylarsinic acid or tributyltin oxide are just some examples. Data on the genotoxicity (and the neurotoxicity) as well as the mechanisms of cellular action of organometal(loid) compounds are, however, scarce. Many studies have shown that the production of such organometal(loid) species is possible and likely whenever anaerobic conditions (at least on a microscale) are combined with available metal(loid)s and methyl donors in the presence of suitable organisms. Such anaerobic conditions can exist within natural environments (e.g., wetlands, pond sediments) as well as within anthropogenic environmental systems (e.g., waste disposal sites and sewage treatments plants). Some methylation can also take place under aerobic conditions. This article gives an overview about the environmental distribution of organometal(loid) compounds and the potential hazardous effects on animal and human health. Genotoxic effects in vivo and in vitro in particular are discussed.

Muscular cramps: proposals for a new classification

Muscle cramps are involuntary, painful, sudden contractions of the skeletal muscles. They are present in normal subjects under certain conditions (during a strong voluntary contraction, sleep, sports, pregnancy) and in several pathologies such as myopathies, neuropathies, motoneuron diseases, metabolic disorders, hydroelectrolyte imbalances or endocrine pathologies. There has been considerable uncertainty in the literature regarding the classification and nomenclature of muscle cramps, both because the term "cramp" is used to indicate a variety of clinical features of muscles, leading to its use as an imprecise "umbrella" term that includes stiffness, contractures and local pain, and because the spectrum of the diseases in which it appears is wide. The purpose of the present study is to propose a simple classification to provide a framework to better recognize the full spectrum of phenomenology of muscle cramps.

Binding of bismuth to serum proteins: implication for targets of Bi(III) in blood plasma

Bismuth complexes have been widely used in clinical treatment as antiulcer drugs. However, different adverse effects have been observed and the diagnosis is generally confirmed by the detection of bismuth in blood or blood plasma. In this study, binding of bismuth to human serum albumin was studied by fluorescence spectroscopy with the binding constant logK(a) to be 11.2. Competitive binding of bismuth to human albumin and transferrin was carried out at pH 7.4 by FPLC and ICP-MS. It was found that over 70% of bismuth binds to transferrin even in the presence of a large excess of albumin (albumin/transferrin=13:1) at pH 7.4, 10 mM bicarbonate. The distribution of bismuth between the two proteins was almost unchanged when Cys(34) of albumin was blocked. However, all bismuth binds to albumin when iron-saturated transferrin was used. Almost all of the bismuth was distributed over the fractions containing transferrin (70%) and albumin (<30%) in serum. The percentage of bismuth associated with transferrin was further increased by 15% with elevated transferrin in serum. Binding of bismuth to transferrin is much stronger than human albumin. Transferrin is probably the major target of bismuth in blood plasma, and it may play a role in the pharmacology of bismuth.

Bismuth-induced lysosomal rupture in J774 cells

Bismuth-containing drugs have several applications, one being their use against Helicobacter pylori-associated peptic ulcers, and bismuth has been discovered in macrophages at the base and margins of peptic ulcers. In the present study, the autometallographic technique for the histochemical demonstration of bismuth was applied, showing that bismuth citrate-exposed J774 cells accumulate the metal in their lysosomes. Such accumulations resulted in lysosomal rupture - assayed by the acridine orange uptake technique and flow cytofluorometry - and ensuing apoptotic cell death.

Transferrin/transferrin receptor-mediated drug delivery

Since transferrin was discovered more than half a century ago, a considerable effort has been made towards understanding tranferrin-mediated iron uptake. However, it was not until recently with the identification and characterization of several new genes related to iron homeostasis, such as the hemochromatosis protein HFE and the iron transporter DMT1, that our knowledge has been advanced dramatically. A major pathway for cellular iron uptake is through internalization of the complex of iron-bound transferrin and the transferrin receptor, which is negatively modulated by HFE, a protein related to hereditary hemochromatosis. Iron is released from transferrin as the result of the acidic pH in endosome and then is transported to the cytosol by DMT1. The iron is then utilized as a cofactor by heme and ribonucleotide reductase or stored in ferritin. Apart from iron, many other metal ions of therapeutic and diagnostic interests can also bind to transferrin at the iron sites and their transferrin complexes can be recognized by many cells. Therefore, transferrin has been thought as a "delivery system" for many beneficial and harmful metal ions into the cells. Transferrin has also be widely applied as a targeting ligand in the active targeting of anticancer agents, proteins, and genes to primary proliferating malignant cells that overexpress transferrin receptors. This is achieved by conjugation of transferrin with drugs, proteins, hybride systems with marcomolecules and as liposomal-coated systems. Conjugates of anticancer drugs with transferrin can significantly improve the selectivity and toxicity and overcome drug resistance, thereby leading to a better treatment. The coupling of DNA to transferrin via a polycation such as polylysine or via cationic liposomes can target and transfer of the extrogenous DNA particularly into proliferating cells through receptor-mediated endocytosis. These kinds of non-viral vectors are potential alternatives to viral vectors for gene therapy, if the transfection efficiency can be improved. Moreover, transferrin receptors have shown potentials in delivery of therapeutic drugs or genes into the brain across blood-brain barrier.

Pathways of proximal tubular cell death in bismuth nephrotoxicity

Colloidal bismuth subcitrate (CBS), a drug for treatment of peptic ulcers, has been reported in the literature to be nephrotoxic in humans when taken in high overdoses. To investigate the mechanism of bismuth nephropathy, we developed an animal model by feeding rats single doses of CBS containing 3.0 mmol Bi/kg body weight. Terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling assay, immunostaining for active caspase-3, and electron microscopy showed that proximal tubular epithelial cells die by necrosis and not by apoptosis within 3 h after CBS administration. Exposure of the renal epithelial cell lines NRK-52E and LLC-PK1 to Bi(3+) in citrate buffer served as an in vitro model of bismuth nephropathy. NRK-52E cells exposed to 100 microM Bi(3+) or more died by necrosis, as was demonstrated by nuclear staining with Hoechst 33258 and flow cytometry using Alexa(488)-labeled Annexin-V and the vital nuclear dye TOPRO-3. Bismuth-induced cell death of NRK-52E cells was not prevented by the caspase-3 inhibitor z-VAD-fmk, whereas this inhibitor did prevent cisplatinum-induced apoptosis. Mitochondrial dysfunction and induction of free radicals were shown not to be involved in bismuth nephrotoxicity. The early time point of damage induction in vitro as well as in vivo and the early displacement of N-cadherin, as found in previous studies, suggest that bismuth induces cell death by destabilizing the cell membrane. In conclusion, we showed that high overdose of bismuth induced cell death by necrosis in vivo as well as in vitro, possibly by destabilization of the cell membrane.

Fanconi's syndrome, acute renal failure, and tonsil ulcerations after colloidal bismuth subcitrate intoxication

A 22-year-old woman ingested 5.4 g of colloidal bismuth subcitrate (CBS) in a suicide attempt. After ingestion, she presented with Fanconi's syndrome and acute renal failure to our unit. On the third day after ingestion, she was anuric. Ulcerations of both tonsils were observed 8 days after intoxication. Sodium-2,3-dimercapto-1-propanesulfonate (DMPS) is shown to be an effective chelating agent of heavy metal intoxications, but it has only a small effect on elimination of bismuth salts in patients with renal insufficiency without hemodialysis. In our case, we initiated hemodialysis and intravenous treatment with DMPS 60 hours after intoxication. By repeated measurements of bismuth concentrations in serum and dialyzed fluid, we showed its successful elimination. Serum bismuth level decreased from 640 microg/L to 15 microg/L within 6 days. With elimination of bismuth, renal function improved, and tonsil ulcerations healed. Hemodialysis was discontinued on day 14. Follow-up examination 6 weeks later showed normal renal function. Clinicians should be aware that acute renal failure and tonsil ulcerations can occur after CBS intoxication. Generally, acute renal failure caused by CBS intoxication is reversible. Treatment with the chelating agent DMPS in combination with hemodialysis is highly effective in reducing the serum bismuth level in patients with acute renal failure.