Pharmacokinetics of experimental pentavalent antimony after intramuscular administration in adult volunteers

Effect of iron cyclic transformation on the natural purification of antimony in contaminated reservoirs of mines

To further understand the purification mechanism of antimony (Sb) in reservoirs, samples of stratified water and bottom interface sediment were collected in this study. The cross-flow ultrafiltration technique was used to separate the truly dissolved (<1 kDa) and colloidal (1 kDa-0.45 μm) phases of water, and two modified sequential extraction techniques were used to determine the Sb and Fe mineral forms in sediment, respectively. The results showed that the total Sb concentration could decrease from 142.2 μg/L in surface water to 98.6 μg/L at 16 m; this was contributed to by the removal of truly dissolved Sb. In comparison to particulate Sb (>0.45 μm), the formation of colloidal Sb played a greater role in the purification process. There was a positive correlation between Sb and Fe in the colloidal phase (r = 0.45, P < 0.05). The generation of colloidal Fe could be promoted by higher temperatures, pH values, DO, and DOC in the upper layer (0-5 m). However, the complexation of DOC with colloidal Fe inhibited the adsorption of truly dissolved Sb. After entering the sediment, the secondary release of Sb could not increase the Sb concentration in the lower layer obviously, while the supplementation of Fe(III) could further enhance Sb natural purification.

A Promising Cutaneous Leishmaniasis Treatment with a Nanoemulsion-Based Cream with a Generic Pentavalent Antimony (Ulamina) as the Active Ingredient

Leishmania parasites are the etiological agents of Leishmaniasis, a tropical disease that affects around 15 million people in about 90 countries. The chosen therapy for this disease is based on antimony V compounds, such as meglumine antimoniate. It can be administered as a parenteral, subcutaneous or perilesional form as successive infiltrations with pre-established doses localized in the border of the granuloma that characterizes the wound of Cutaneous Leishmaniasis (CL). Herein, a topical pharmaceutical recipe, such as an emulsion, is proposed to eliminate the trauma caused by administering the medicine in parenteral form to the face or other difficult access zones. The evaluation of this vehicle was performed by analyzing parameters such as pH, viscosity, homogeneity and droplet size distribution. Furthermore, the effectiveness of the emulsion was proved by in vitro experiments using Strat-M synthetic membranes, showing that the transdermal passage of the antimonial complex is guaranteed. Moreover, complete healing of the wound has been attained in patients with CL, as shown with two clinical cases in this article.

Soil migration of antimony and arsenic facilitated by colloids in lysimeter studies

The migration behaviors of antimony (Sb) and arsenic (As) and its influence factors have not been well understood among the different soils. In this study, we used lysimeter experiments to investigate the migration behavior of Sb compared with that of As in four representative soil materials from China. All the experiments processes and management measures were conducted to simulate the actual natural environmental conditions. Results indicated that after two years of leaching, the concentrations of Sb and As at the soil surface had decreased, whereas they increased in the deep soil profiles. In the polluted soil materials, 28.5%-39.2% of Sb and 0.4%-1.3% of As existed in the stable fraction, respectively. As and Sb levels were higher in the surface soil layer, and decreased with the soil depth in the different soil profiles. In soil leachate, Sb was mainly found in particle sizes smaller than 0.45 μm with the organic colloids, which had a peak in the spring and summer. On contrast, As was found in particle sizes larger than 0.45 μm with the inorganic colloids such as iron (Fe) and aluminum (Al) oxides. Pearson correlation results showed that the concentrations of Sb in the soil leaching solution and 0.45-μm-filltered solution were all positively correlated with Fe and Al. The results confirmed that Sb was combined with Fe and Al in the solution, and As posed a greater environmental risk than Sb during the leaching process. This study will help us to describe and predict As and Sb pollution in the soil environment, providing a basis for managing soil contaminated by these pollutants.

Clinical Pharmacokinetics of Systemically Administered Antileishmanial Drugs

This review describes the pharmacokinetic properties of the systemically administered antileishmanial drugs pentavalent antimony, paromomycin, pentamidine, miltefosine and amphotericin B (AMB), including their absorption, distribution, metabolism and excretion and potential drug–drug interactions. This overview provides an understanding of their clinical pharmacokinetics, which could assist in rationalising and optimising treatment regimens, especially in combining multiple antileishmanial drugs in an attempt to increase efficacy and shorten treatment duration. Pentavalent antimony pharmacokinetics are characterised by rapid renal excretion of unchanged drug and a long terminal half-life, potentially due to intracellular conversion to trivalent antimony. Pentamidine is the only antileishmanial drug metabolised by cytochrome P450 enzymes. Paromomycin is excreted by the kidneys unchanged and is eliminated fastest of all antileishmanial drugs. Miltefosine pharmacokinetics are characterized by a long terminal half-life and extensive accumulation during treatment. AMB pharmacokinetics differ per drug formulation, with a fast renal and faecal excretion of AMB deoxylate but a much slower clearance of liposomal AMB resulting in an approximately ten-fold higher exposure. AMB and pentamidine pharmacokinetics have never been evaluated in leishmaniasis patients. Studies linking exposure to effect would be required to define target exposure levels in dose optimisation but have only been performed for miltefosine. Limited research has been conducted on exposure at the drug’s site of action, such as skin exposure in cutaneous leishmaniasis patients after systemic administration. Pharmacokinetic data on special patient populations such as HIV co-infected patients are mostly lacking. More research in these areas will help improve clinical outcomes by informed dosing and combination of drugs.

Anaerobic Bacterial Immobilization and Removal of Toxic Sb(III) Coupled With Fe(II)/Sb(III) Oxidation and Denitrification

Antimony (Sb) pollution is a worldwide problem. In some anoxic sites, such as Sb mine drainage and groundwater sediment, the Sb concentration is extremely elevated. Therefore, effective Sb remediation strategies are urgently needed. In contrast to microbial aerobic antimonite [Sb(III)] oxidation, the mechanism of microbial anaerobic Sb(III) oxidation and the effects of nitrate and Fe(II) on the fate of Sb remain unknown. In this study, we discovered the mechanism of anaerobic Sb(III) oxidation coupled with Fe(II) oxidation and denitrification in the facultative anaerobic Sb(III) oxidizer Sinorhizobium sp. GW3. We observed the following: (1) under anoxic conditions with nitrate as the electron acceptor, strain GW3 was able to oxidize both Fe(II) and Sb(III) during cultivation; (2) in the presence of Fe(II), nitrate and Sb(III), the anaerobic Sb(III) oxidation rate was remarkably enhanced, and Fe(III)-containing minerals were produced during Fe(II) and Sb(III) oxidation; (3) qRT-PCR, gene knock-out and complementation analyses indicated that the arsenite oxidase gene product AioA plays an important role in anaerobic Sb(III) oxidation, in contrast to aerobic Sb(III) oxidation; and (4) energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (XRD) analyses revealed that the microbially produced Fe(III) minerals were an effective chemical oxidant responsible for abiotic anaerobic Sb(III) oxidation, and the generated Sb(V) was adsorbed or coprecipitated on the Fe(III) minerals. This process included biotic and abiotic factors, which efficiently immobilize and remove soluble Sb(III) under anoxic conditions. The findings revealed a significantly novel development for understanding the biogeochemical Sb cycle. Microbial Sb(III) and Fe(II) oxidation coupled with denitrification has great potential for bioremediation in anoxic Sb-contaminated environments.

Successful treatment against American cutaneous leishmaniasis by intralesional infiltration of a generic antimonial compound-lidocaine combination. A follow up study

One hundred and twenty-two lesions caused by Leishmania braziliensis in 92 patients were treated using weekly intralesional (IL) infiltrations of a generic pentavalent antimonial compound, combined with local anesthetics. The topical therapy produced satisfactory healing in all the included patients, bearing from single-small ulcers to multiple or big lesions, after receiving an average 6 ± 3 IL infiltrations (90 mgSb⁵⁺each). The rapid effect of this compound was demonstrated by the observed decrease of the Leishmania-amastigote population following microscopical grading in complicated ulcers after receiving two infiltrations. Neither discomfort nor side effects after infiltrations were recorded from the treated patients at any time. In addition, no signs of cutaneous relapse or mucosal lesion were detected during follow up after a decade clinical healing in 22% of the treated patients. Investment to produce the generic antimonial-IL treatment resulted significantly lower than the standard antimonial systemic therapy, and its cost/risk is discussed. The minimal dose of Sb⁵⁺ causing non-side effects or patient discomfort, the low production cost and the here demonstrated successful results, lead us to propose this generic antimonial compound as an alternative therapy for leishmanial-control in areas where American cutaneous leishmaniasis is endemic.

Lack of Clinical Pharmacokinetic Studies to Optimize the Treatment of Neglected Tropical Diseases: A Systematic Review

INTRODUCTION

Neglected tropical diseases (NTDs) affect more than one billion people, mainly living in developing countries. For most of these NTDs, treatment is suboptimal. To optimize treatment regimens, clinical pharmacokinetic studies are required where they have not been previously conducted to enable the use of pharmacometric modeling and simulation techniques in their application, which can provide substantial advantages.

OBJECTIVES

Our aim was to provide a systematic overview and summary of all clinical pharmacokinetic studies in NTDs and to assess the use of pharmacometrics in these studies, as well as to identify which of the NTDs or which treatments have not been sufficiently studied.

METHODS

PubMed was systematically searched for all clinical trials and case reports until the end of 2015 that described the pharmacokinetics of a drug in the context of treating any of the NTDs in patients or healthy volunteers.

RESULTS

Eighty-two pharmacokinetic studies were identified. Most studies included small patient numbers (only five studies included >50 subjects) and only nine (11 %) studies included pediatric patients. A large part of the studies was not very recent; 56 % of studies were published before 2000. Most studies applied non-compartmental analysis methods for pharmacokinetic analysis (62 %). Twelve studies used population-based compartmental analysis (15 %) and eight (10 %) additionally performed simulations or extrapolation. For ten out of the 17 NTDs, none or only very few pharmacokinetic studies could be identified.

CONCLUSIONS

For most NTDs, adequate pharmacokinetic studies are lacking and population-based modeling and simulation techniques have not generally been applied. Pharmacokinetic clinical trials that enable population pharmacokinetic modeling are needed to make better use of the available data. Simulation-based studies should be employed to enable the design of improved dosing regimens and more optimally use the limited resources to effectively provide therapy in this neglected area.

Abiotic and biotic factors responsible for antimonite oxidation in Agrobacterium tumefaciens GW4

Antimonite [Sb(III)]-oxidizing bacteria can transform the toxic Sb(III) into the less toxic antimonate [Sb(V)]. Recently, the cytoplasmic Sb(III)-oxidase AnoA and the periplasmic arsenite [As(III)] oxidase AioAB were shown to responsible for bacterial Sb(III) oxidation, however, disruption of each gene only partially decreased Sb(III) oxidation efficiency. This study showed that in Agrobacterium tumefaciens GW4, Sb(III) induced cellular H₂O₂ content and H₂O₂ degradation gene katA. Gene knock-out/complementation of katA, anoA, aioA and anoA/aioA and Sb(III) oxidation and growth experiments showed that katA, anoA and aioA were essential for Sb(III) oxidation and resistance and katA was also essential for H₂O₂ resistance. Furthermore, linear correlations were observed between cellular H₂O₂ and Sb(V) content in vivo and chemical H₂O₂ and Sb(V) content in vitro (R² = 0.93 and 0.94, respectively). These results indicate that besides the biotic factors, the cellular H₂O₂ induced by Sb(III) also catalyzes bacterial Sb(III) oxidation as an abiotic oxidant. The data reveal a novel mechanism that bacterial Sb(III) oxidation is associated with abiotic (cellular H₂O₂) and biotic (AnoA and AioAB) factors and Sb(III) oxidation process consumes cellular H₂O₂ which contributes to microbial detoxification of both Sb(III) and cellular H₂O₂.

Alterations in Evoked Otoacoustic Emissions by the Use of Meglumine Antimoniate in American Tegumentary Leishmaniasis Patients

INTRODUCTION

Tegumentary Leishmaniasis (TL) is a neglected, non-contagious, infectious disease, caused by different protozoa species of the Leishmania genus that affects skin and mucous membranes. Meglumine Antimoniate (MA), the first drug of choice for TL treatment in Brazil, has already been associated with cochlear toxicity, which is defined as damages of the cochlea caused by exposure to chemical substances, resulting in reversible or irreversible hearing loss. Auditory monitoring for cochlear toxicity aims at the early detection of auditory disorders, enabling, when possible, hearing to be preserved or an early auditory rehabilitation. Although otoacoustic emissions (OAEs) are used in this monitoring, there is no consensus on the criteria that define cochlear toxicity by this examination. The objective of this study was to describe the characteristics of the OAEs in cochlear toxicity monitoring in TL patients using MA.

METHODS

Prospective and longitudinal study of auditory monitoring of 35 patients with parasitological diagnosis of TL, with liminal tonal audiometry, high frequency audiometry, immitanciometry, distortion product evoked otoacoustic emissions (DPEOAEs) and transient evoked otoacoustic emissions (TEOAEs) before treatment, at the end of treatment, one month after the end of treatment and two months after the end of treatment.

RESULTS

80% male, with median age of 44 years (IIQ: 22-59). In the pre-treatment evaluation: 11.4% complained of hearing loss and 20% of tinnitus, 48.6% presented auditory alterations in liminal tonal audiometry (LTA, 65.2% in high frequency audiometry (HFA), 26.6% in DPEOAE and 51.4% in TEOAE. No association was verified between genre and alterations in the EOAE examinations. We observed that patients that presented disorders in DPEOAE examinations were 17 years older than those without alterations and that patients that showed disorders in TEOAEO examinations were 34 years older than those without disorders. The presence of alterations in DPEOAE and TEOAE before beginning treatment was associated with each other and with the presence of alterations in LTA and HFA, and only DPEOAE was associated with hearing loss. We observed a significantly higher number of alterations of DPEOAE at the end of treatment than during pre-treatment and values of the ratio signal/noise significantly smaller at the end of treatment than during pre-treatment in the frequencies of 2 kHz (difference of 1.7dB; p = 0.016) and 4 kHz (difference of 2.45dB; p = 0.016) in DPEOAE and in the range 1.75/2.5 kHz in TEOAE (difference of 2.9dB; p = 0.039).

CONCLUSION

The ototoxic signals observed in our study using EOAE indicated that both, DPEOAE and TEOAE are adequate and sensitive techniques for clinical monitoring of ototoxicity by MA. Their application is very simple, and their results help the physician to take the most adequate steps for each patient, thus avoiding permanent hearing damage.

Microbial Antimony Biogeochemistry: Enzymes, Regulation, and Related Metabolic Pathways

Antimony (Sb) is a toxic metalloid that occurs widely at trace concentrations in soil, aquatic systems, and the atmosphere. Nowadays, with the development of its new industrial applications and the corresponding expansion of antimony mining activities, the phenomenon of antimony pollution has become an increasingly serious concern. In recent years, research interest in Sb has been growing and reflects a fundamental scientific concern regarding Sb in the environment. In this review, we summarize the recent research on bacterial antimony transformations, especially those regarding antimony uptake, efflux, antimonite oxidation, and antimonate reduction. We conclude that our current understanding of antimony biochemistry and biogeochemistry is roughly equivalent to where that of arsenic was some 20 years ago. This portends the possibility of future discoveries with regard to the ability of microorganisms to conserve energy for their growth from antimony redox reactions and the isolation of new species of "antimonotrophs."

Correlating microbial community profiles with geochemical conditions in a watershed heavily contaminated by an antimony tailing pond

Mining activities have introduced various pollutants to surrounding aquatic and terrestrial environments, causing adverse impacts to the environment. Indigenous microbial communities are responsible for the biogeochemical cycling of pollutants in diverse environments, indicating the potential for bioremediation of such pollutants. Antimony (Sb) has been extensively mined in China and Sb contamination in mining areas has been frequently encountered. To date, however, the microbial composition and structure in response to Sb contamination has remained overlooked. Sb and As frequently co-occur in sulfide-rich ores, and co-contamination of Sb and As is observed in some mining areas. We characterized, for the first time, the microbial community profiles and their responses to Sb and As pollution from a watershed heavily contaminated by Sb tailing pond in Southwest China. The indigenous microbial communities were profiled by high-throughput sequencing from 16 sediment samples (535,390 valid reads). The comprehensive geochemical data (specifically, physical-chemical properties and different Sb and As extraction fractions) were obtained from river water and sediments at different depths as well. Canonical correspondence analysis (CCA) demonstrated that a suite of in situ geochemical and physical factors significantly structured the overall microbial community compositions. Further, we found significant correlations between individual phylotypes (bacterial genera) and the geochemical fractions of Sb and As by Spearman rank correlation. A number of taxonomic groups were positively correlated with the Sb and As extractable fractions and various Sb and As species in sediment, suggesting potential roles of these phylotypes in Sb biogeochemical cycling.

Clinical and Parasitological Features of Patients with American Cutaneous Leishmaniasis that Did Not Respond to Treatment with Meglumine Antimoniate

BACKGROUND

American cutaneous leishmaniasis (ACL) is a complicated disease producing about 67.000 new cases per year. The severity of the disease depends on the parasite species; however in the vast majority of cases species confirmation is not feasible. WHO suggestion for ACL produced by Leishmania braziliensis, as first line treatment, are pentavalent antimonial derivatives (Glucantime or Sodium Stibogluconate) under systemic administration. According to different authors, pentavalent antimonial derivatives as treatment for ACL show a healing rate of about 75% and reasons for treatment failure are not well known.

METHODS

In order to characterise the clinical and parasitological features of patients with ACL that did not respond to Glucantime, a cross-sectional observational study was carried out in a cohort of 43 patients recruited in three of the Colombian Army National reference centers for complicated ACL. Clinical and paraclinical examination, and epidemiological and geographic information were recorded for each patient. Parasitological, histopathological and PCR infection confirmation were performed. Glucantime IC50 and in vitro infectivity for the isolated parasites were estimated.

RESULTS

Predominant infecting Leishmania species corresponds to L. braziliensis (95.4%) and 35% of the parasites isolated showed a significant decrease in in vitro Glucanatime susceptibility associated with previous administration of the medicament. Lesion size and in vitro infectivity of the parasite are negatively correlated with decline in Glucantime susceptibility (Spearman: r = (-)0,548 and r = (-)0,726; respectively).

CONCLUSION

A negative correlation between lesion size and parasite resistance is documented. L. braziliensis was found as the main parasite species associated to lesion of patients that underwent treatment failure or relapse. The indication of a second round of treatment in therapeutic failure of ACL, produced by L. braziliensis, with pentavalent antimonial derivatives is discussable.

Factors associated to adherence to different treatment schemes with meglumine antimoniate in a clinical trial for cutaneous leishmaniasis

The favorable outcome of the treatment of a disease is influenced by the adherence to therapy. Our objective was to assess factors associated with adherence to treatment of patients included in a clinical trial of equivalence between the standard and alternative treatment schemes with meglumine antimoniate (MA) in the treatment of cutaneous leishmaniasis (CL), in the state of Rio de Janeiro. Between 2008 and 2011, 57 patients with CL were interviewed using a questionnaire to collect socioeconomic data. The following methods were used for adherence monitoring: counting of vial surplus, monitoring card, Morisky test and modified Morisky test (without the question regarding the schedule); we observed 82.1% (vial return), 86.0% (monitoring card), 66.7% (Morisky test) and 86.0% (modified Morisky test) adherence. There was a strong correlation between the method of vial counting and the monitoring card and modified Morisky test. A significant association was observed between greater adherence to treatment and low dose of MA, as well as with a lower number of people sleeping in the same room. We recommend the use of the modified Morisky test to assess adherence to treatment of CL with MA, because it is a simple method and with a good performance, when compared to other methods.

Skermanella stibiiresistens sp. nov., a highly antimony-resistant bacterium isolated from coal-mining soil, and emended description of the genus Skermanella

A Gram-negative, aerobic, motile, rod-shaped, antimony-resistant bacterium, designated strain SB22T, was isolated from soil of Jixi coal mine, China. The major cellular fatty acids (>5 %) were C18 : 1ω7c (63.5 %), summed feature 2 (C14 : 0 3-OH and/or iso-C16 : 1 I, 10.8 %) and C16 : 0 (9.9 %). The major polar lipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and an unknown aminolipid. The genomic DNA G+C content was 69.6 mol% and Q-10 was the major respiratory quinone. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain SB22T was most closely related to Skermanella aerolata 5416T-32T (97.3 %), Skermanella parooensis ACM 2042T (95.8 %) and Skermanella xinjiangensis 10-1-101T (92.9 %). The DNA–DNA hybridization value between strain SB22T and S. aerolata KACC 11604T ( = 5416T-32T) was 43.3 %. On the basis of phenotypic, chemotaxonomic and phylogenetic characteristics of strain SB22T and related species, it is considered that the isolate represents a novel species of the genus Skermanella , for which the name Skermanella stibiiresistens sp. nov. is proposed. The type strain is SB22T ( = CGMCC 1.10751T = KCTC 23364T). An emended description of the genus Skermanella is provided.

The chemistry and behaviour of antimony in the soil environment with comparisons to arsenic: a critical review

This article provides a critical review of the environmental chemistry of inorganic antimony (Sb) in soils, comparing and contrasting findings with those of arsenic (As). Characteristics of the Sb soil system are reviewed, with an emphasis on speciation, sorption and phase associations, identifying differences between Sb and As behaviour. Knowledge gaps in environmentally relevant Sb data for soils are identified and discussed in terms of the limitations this imposes on understanding the fate, behaviour and risks associated with Sb in environmental soil systems, with particular reference to mobility and bioavailability.