Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 171
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Regul Toxicol Pharmacol ; 112: 104569, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31927005

RESUMO

Oseltamivir is an antiviral drug approved to treat influenza in humans. Although the dosing regimen of this drug is well established for non-pregnant patients, it is not clear if the significant physiological alterations associated with pregnancy affect the pharmacokinetics of oseltamivir and, thus, warrant different dosing regimens to assure efficacy. In this study, we investigated the suitability of rhesus macaques as an animal model for studying oseltamivir pharmacokinetics during all trimesters of pregnancy in comparison to pre-pregnant conditions. Specifically, we compared the pharmacokinetics of oseltamivir and its pharmacologically active metabolite oseltamivir carboxylate in rhesus monkeys after intravenous and nasogastric administration of 2.5 mg oseltamivir phosphate/kg body weight given prior to and during the first, second, and third trimesters of pregnancy. Pregnancy had only a modest effect upon the pharmacokinetic parameters of oseltamivir and oseltamivir carboxylate. Monkeys treated intravenously in the third trimester had a reduction in Vd and CL, compared to non-pregnant monkeys. These changes did not occur in the other two trimesters. Pregnant monkeys treated intravenously had 20-25% decrease in AUC0-∞ of oseltamivir carboxylate and a corresponding increase in Vd and CL. Pregnant monkeys treated nasogastrically with oseltamivir phosphate demonstrated a pattern that recapitulated intravenous dosing. Taken together these data indicate that rhesus monkeys are an acceptable model for studying drug-pregnancy interactions.

2.
Toxicol Appl Pharmacol ; 388: 114878, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31923437

RESUMO

Our previous report on pharmacokinetic (PK) evaluation of 6:2 fluorotelomer alcohol (6:2 FTOH) examined the biopersistence potential of its metabolites based on data published from single inhalation and occupational 6:2 FTOH exposure studies. We calculated internal exposure estimates of three key metabolites of 6:2 FTOH, of which 5:3 fluorotelomer carboxylic acid (5:3 acid) had the highest internal exposure and the slowest clearance. No oral repeated 6:2 FTOH exposure data were available at the time to fully characterize the biopersistence potential of the metabolite 5:3 acid. We recently received additional data on 6:2 FTOH and 5:3 acid, which included a 90-day toxicokinetic study report on repeated oral 6:2 FTOH exposure to rats. We reviewed the study and analyzed the reported 5:3 acid concentrations in plasma, liver, and fat using one-compartment PK modeling and calculated elimination rate constants (kel), elimination half-lives (t1/2) and times to steady state (tss) of 5:3 acid at three 6:2 FTOH doses. Our results showed that tss of 5:3 acid in plasma and evaluated tissues were approximately close to 1 year, such that the majority of highest values were observed at the lowest 6:2 FTOH dose, indicating its association with the biopersistence of 6:2 FTOH. The results of our PK analysis are the first to characterize biopersistence potential of the 5:3 acid after repeated oral exposure to the parent compound 6:2 FTOH based on steady state PK parameters, and therefore, may have an impact on future study designs when conducting toxicity assays for such compounds.

3.
Toxicol Appl Pharmacol ; 386: 114826, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31730783

RESUMO

The widespread use and high abuse liability of tobacco products has received considerable public health attention, in particular for youth, who are vulnerable to nicotine addiction. In this study, adult and adolescent squirrel monkeys were used to evaluate age-related metabolism and pharmacokinetics of nicotine after intravenous administration. A physiologically-based pharmacokinetic (PBPK) model was created to characterize the pharmacokinetic behaviors of nicotine and its metabolites, cotinine, trans-3'-hydroxycotinine (3'-OH cotinine), and trans-3'-hydroxycotinine glucuronide (3'-OH cotinine glucuronide) for both adult and adolescent squirrel monkeys. The PBPK nicotine model was first calibrated for adult squirrel monkeys utilizing in vitro nicotine metabolic data, plasma concentration-time profiles and cumulative urinary excretion data for nicotine and metabolites. Further model refinement was conducted when the calibrated adult model was scaled to the adolescents, because adolescents appeared to clear nicotine and cotinine more rapidly relative to adults. More specifically, the resultant model parameters representing systemic clearance of nicotine and cotinine for adolescent monkeys were approximately two- to three-fold of the adult values on a per body weight basis. The nonhuman primate PBPK model in general captured experimental observations that were used for both model calibration and evaluation, with acceptable performance metrics for precision and bias. The model also identified differences in nicotine pharmacokinetics between adolescent and adult nonhuman primates which might also be present in humans.

4.
Contemp Clin Trials Commun ; 16: 100468, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31701042

RESUMO

Many people with HIV (PWH) experience chronic pain that limits daily function and quality of life. PWH with chronic pain have commonly been prescribed opioids, sometimes for many years, and it is unclear if and how the management of these legacy patients should change in light of the current US opioid epidemic. Guidelines, such as the Centers for Disease Control and Prevention Guideline for Prescribing Opioids for Chronic Pain (CDCG), provide recommendations for the management of such patients but have yet to be translated into easily implementable interventions; there is also a lack of strong evidence that adhering to these recommendations improves patient outcomes such as amount of opioid use and pain levels. Herein we describe the development and preliminary testing of a theory-based intervention, called TOWER (TOWard SafER Opioid Prescribing), designed to support HIV primary care providers in CDCG-adherent opioid prescribing practices with PWH who are already prescribed opioids for chronic pain. TOWER incorporates the content of the CDCG into the theoretical and operational framework of the Information Motivation and Behavioral Skills (IMB) model of health-related behavior. The development process included elicitation research and incorporation of feedback from providers and PWH; testing is being conducted via an adaptive feasibility clinical trial. The results of this process will form the basis of a large, well-powered clinical trial to test the effectiveness of TOWER in promoting CDCG-adherent opioid prescribing practices and improving outcomes for PWH with chronic pain.

5.
Stat Med ; 38(30): 5565-5586, 2019 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-31691322

RESUMO

In longitudinal clinical trials, it is common that subjects may permanently withdraw from the study (dropout), or return to the study after missing one or more visits (intermittent missingness). It is also routinely encountered in HIV prevention clinical trials that there is a large proportion of zeros in count response data. In this paper, a sequential multinomial model is adopted for dropout and subsequently a conditional model is constructed for intermittent missingness. The new model captures the complex structure of missingness and incorporates dropout and intermittent missingness simultaneously. The model also allows us to easily compute the predictive probabilities of different missing data patterns. A zero-inflated Poisson mixed-effects regression model is assumed for the longitudinal count response data. We also propose an approach to assess the overall treatment effects under the zero-inflated Poisson model. We further show that the joint posterior distribution is improper if uniform priors are specified for the regression coefficients under the proposed model. Variations of the g-prior, Jeffreys prior, and maximally dispersed normal prior are thus established as remedies for the improper posterior distribution. An efficient Gibbs sampling algorithm is developed using a hierarchical centering technique. A modified logarithm of the pseudomarginal likelihood and a concordance based area under the curve criterion are used to compare the models under different missing data mechanisms. We then conduct an extensive simulation study to investigate the empirical performance of the proposed methods and further illustrate the methods using real data from an HIV prevention clinical trial.

6.
Toxicol Appl Pharmacol ; 382: 114759, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31521730

RESUMO

The use of toxicokinetic (TK) data is becoming more prevalent in the evaluation of food ingredient safety as more TK information is being incorporated in safety data packages. Data demonstrating "1) the extent of absorption, 2) tissue distribution, 3) pathways and rates of metabolism, and 4) rate(s) of elimination" of food ingredients and their metabolites of intermediate and high toxicological potential may be useful for planning and designing toxicity studies, selecting doses for toxicity studies, addressing species differences, and understanding the potential modes of action to evaluate their safety. TK data reported in the literature or generated from mechanistic TK studies can be analyzed using mathematical methods, including compartment and noncompartment TK methods, whose predictions can enhance interpretation of observed effects. Because of recent advancements, several approaches have been developed to improve sensitivity of analyses of available TK data and reduce uncertainty for evaluating safety of food ingredients. An example of advanced TK methods is physiologically-based TK (PBTK) modeling that incorporates physiological/biochemical parameters into a TK framework to predict internal exposure. In this review, we discuss the utility of some TK methods and explore their relevance and potential value for food ingredient safety evaluation. We also describe the strengths and limitations of these TK methods and discuss current challenges and opportunities for expanding their application for evaluating safety of food ingredients. This review represents a state of science report, and not a guidance document, on the utility and relevance of TK methods for the safety evaluation of food ingredients.

7.
Food Chem Toxicol ; 123: 28-41, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30342114

RESUMO

Arsenic is a ubiquitous contaminant, with typical human dietary intake below 1 µg/kg bw/d and extreme drinking water exposures up to ∼50 µg/kg bw/d. The formation and binding of trivalent metabolites are central to arsenic toxicity and strong human evidence suggests special concern for early life exposures in the etiology of adult diseases, especially cancer. This study measured the metabolism and disposition of arsenite in neonatal mice to understand the role of maturation in metabolic activation and detoxification of arsenic. Many age-related differences were observed after gavage administration of arsenite, with consistent evidence in blood and tissues for higher exposures to trivalent arsenic species in neonatal mice related to the immaturity of metabolic and/or excretory functions. The evidence for greater tissue binding of arsenic species in young mice is consistent with enhanced susceptibility to toxicity based on metabolic and toxicokinetic differences alone. Lactational transfer from arsenite-dosed dams to suckling mice was minimal, based on no dosing-related changes in the levels of arsenic species in pup blood or milk collected from the dams. Animal models evaluating whole-life exposure to inorganic arsenic must use direct dosing in early neonatal life to predict accurately potential toxicity from early life exposures in children.


Assuntos
Intoxicação por Arsênico/metabolismo , Arsenicais/metabolismo , Arsenitos/metabolismo , Leite/química , Compostos de Sódio/metabolismo , Animais , Intoxicação por Arsênico/fisiopatologia , Arsenicais/química , Arsenitos/química , Feminino , Contaminação de Alimentos , Humanos , Lactação , Masculino , Camundongos , Leite/metabolismo , Compostos de Sódio/química , Distribuição Tecidual , Toxicocinética
8.
CPT Pharmacometrics Syst Pharmacol ; 8(3): 158-166, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30520273

RESUMO

The objective of this study was to develop pediatric physiologically based pharmacokinetic (PBPK) models for pantoprazole and esomeprazole. Pediatric PBPK models were developed by Simcyp version 15 by incorporating cytochrome P450 (CYP)2C19 maturation and auto-inhibition. The predicted-to-observed pantoprazole clearance (CL) ratio ranged from 0.96-1.35 in children 1-17 years of age and 0.43-0.70 in term infants. The predicted-to-observed esomeprazole CL ratio ranged from 1.08-1.50 for children 6-17 years of age, and 0.15-0.33 for infants. The prediction was markedly improved by assuming no auto-inhibition of esomeprazole in infants in the PBPK model. Our results suggested that the CYP2C19 auto-inhibition model was appropriate for esomeprazole in adults and older children but could not be directly extended to infants. A better understanding of the complex interplay of enzyme maturation, inhibition, and compensatory mechanisms for CYP2C19 is necessary for PBPK modeling in infants.

9.
J Theor Biol ; 461: 215-229, 2019 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-30393109

RESUMO

Chronic exposure to inorganic arsenic (iAs), a contaminant of water and food supplies, is associated with many adverse health effects. A notable feature of iAs metabolism is sequential methylation reactions which produce mono- and di-methylated arsenicals that can contain arsenic in either the trivalent (III) or pentavalent (V) valence states. Because methylated arsenicals containing trivalent arsenic are more potent toxicants than their pentavalent counterparts, the ability to distinguish between the +3 and +5 valence states is a crucial property for physiologically based pharmacokinetic (PBPK) models of arsenicals to possess if they are to be of use in risk assessment. Unfortunately, current analytic techniques for quantifying arsenicals in tissues disrupt the valence state; hence, pharmacokinetic studies in animals, used for model calibration, only reliably provide data on the sum of the +3 and +5 valence forms of a given metabolite. In this paper we show how mathematical modeling can be used to overcome this obstacle and present a PBPK model for the dimethylated metabolite of iAs, which exists as either dimethylarsinous acid, (CH3)2AsIIIOH (abbreviated DMAIII) or dimethylarsinic acid, (CH3)2AsV(O)OH (abbreviated DMAV). The model distinguishes these two forms and sets a lower bound on how much of an organ's DMA burden is present in the more reactive and toxic trivalent valence state. We conjoin the PBPK model to a simple model for DMAIII-induced oxidative stress in liver and use this extended model to predict cytotoxicity in liver in response to the high oral dose of DMAV. The model incorporates mechanistic details derived from in vitro studies and is iteratively calibrated with lumped-valence-state PK data for intravenous or oral dosing with DMAV. Model formulation leads us to predict that orally administered DMAV undergoes extensive reduction in the gastrointestinal (GI) tract to the more toxic trivalent DMAIII.

10.
Drug Metab Dispos ; 47(3): 296-313, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30567878

RESUMO

A thorough knowledge of the newborn (age, birth to 1 month postpartum) infant's gastrointestinal tract (GIT) is critical to the evaluation of the absorption, distribution, metabolism, and excretion (ADME) of orally administered drugs in this population. Developmental changes in the GIT during the newborn period are important for nutrient uptake as well as the disposition of orally administered medications. Some aspects of gastrointestinal function do not mature until driven by increased dietary complexity and nutritional demands later in the postnatal period. The functionalities present at birth, and subsequent maturation, can also impact the ADME parameters of orally administered compounds. This review will examine some specific contributors to the ADME processes in human neonates, as well as what is currently understood about the drivers for their maturation. Key species differences will be highlighted, with a focus on laboratory animals used in juvenile toxicity studies. Because of the gaps and inconsistencies in our knowledge, we will also highlight areas where additional study is warranted to better inform the appropriate use of medicines specifically intended for neonates.


Assuntos
Desenvolvimento Infantil/fisiologia , Trato Gastrointestinal/fisiologia , Absorção Intestinal/fisiologia , Taxa de Depuração Metabólica/fisiologia , Administração Oral , Fatores Etários , Animais , Humanos , Recém-Nascido , Modelos Animais , Distribuição Tecidual/fisiologia
11.
Food Chem Toxicol ; 121: 676-686, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30278242

RESUMO

Arsenic is a ubiquitous contaminant, with typical dietary intake below 1 µg/kg bw/d and drinking water exposures up to 50 µg/kg bw/d. Arsenic exposures are associated with human diseases and doses of toxicological concern are similar to typical dietary intake. Metabolism of arsenite to dimethylarsinate (DMAV) by arsenite-3-methyltransferase (As3MT) promotes clearance, but also generates reactive trivalent intermediates that bind extensively to cellular thiols. This study measured pentavalent and trivalent arsenic species in blood and tissues after oral and intravenous administration of arsenite (50 µg/kg bw). After oral administration, the intestine and liver contained elevated levels of AsIII and MMAIII, relative to erythrocytes, lung, and kidney, suggesting incomplete conversion to DMA during first-pass metabolism. However, blood concentrations of the predominant species, DMA, were similar for oral and intravenous dosing. While all tissues examined contained DMAIII, muscle, brain, and plasma had undetectable levels of MMAIII. Tissue levels of arsenic species were similar following intravenous vs. oral administration, except lower in the intestine. The results confirm the role of metabolism in producing fluxes of putatively toxic trivalent arsenic intermediates. Tissue dosimetry suggests that the intestine, liver, lung, and kidney could be more susceptible to effects of bound arsenic, relative to muscle and brain.


Assuntos
Arsênico/classificação , Arsenitos/farmacocinética , Compostos de Sódio/farmacocinética , Administração Oral , Animais , Área Sob a Curva , Arsênico/química , Arsenitos/química , Eritrócitos , Feminino , Meia-Vida , Injeções Intravenosas , Camundongos , Reprodutibilidade dos Testes , Compostos de Sódio/química
12.
Birth Defects Res ; 110(11): 916-932, 2018 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-29536674

RESUMO

Physiologically based pharmacokinetic (PBPK) models are developed from compound-independent information to describe important anatomical and physiological characteristics of an individual or population of interest. Modeling pediatric populations is challenging because of the rapid changes that occur during growth, particularly in the first few weeks and months after birth. Neonates who are born premature pose several unique challenges in PBPK model development. To provide appropriate descriptions for body weight (BW) and height (Ht) for age and appropriate incremental gains in PBPK models of the developing preterm and full term neonate, anthropometric measurements collected longitudinally from 1,063 preterm and 158 full term neonates were combined with 2,872 cross-sectional measurements obtained from the NHANES 2007-2010 survey. Age-specific polynomial growth equations for BW and Ht were created for male and female neonates with corresponding gestational birth ages of 25, 28, 31, 34, and 40 weeks. Model-predicted weights at birth were within 20% of published fetal/neonatal reference standards. In comparison to full term neonates, postnatal gains in BW and Ht were slower in preterm subgroups, particularly in those born at earlier gestational ages. Catch up growth for BW in neonates born at 25, 28, 31, and 34 weeks gestational age was complete by 13, 8, 6, and 2 months of life (males) and by 10, 6, 5, and 2 months of life (females), respectively. The polynomial growth equations reported in this paper represent extrauterine growth in full term and preterm neonates and differ from the intrauterine growth standards that were developed for the healthy unborn fetus.


Assuntos
Estatura , Peso Corporal , Crescimento e Desenvolvimento , Recém-Nascido Prematuro/crescimento & desenvolvimento , Nascimento Prematuro/fisiopatologia , Pré-Escolar , Feminino , Idade Gestacional , Humanos , Lactente , Recém-Nascido , Estudos Longitudinais , Masculino , Padrões de Referência
14.
Toxicol Sci ; 162(2): 341-348, 2018 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-29385573

RESUMO

The development and application of physiologically based pharmacokinetic (PBPK) models in chemical toxicology have grown steadily since their emergence in the 1980s. However, critical evaluation of PBPK models to support public health decision-making across federal agencies has thus far occurred for only a few environmental chemicals. In order to encourage decision-makers to embrace the critical role of PBPK modeling in risk assessment, several important challenges require immediate attention from the modeling community. The objective of this contemporary review is to highlight 3 of these challenges, including: (1) difficulties in recruiting peer reviewers with appropriate modeling expertise and experience; (2) lack of confidence in PBPK models for which no tissue/plasma concentration data exist for model evaluation; and (3) lack of transferability across modeling platforms. Several recommendations for addressing these 3 issues are provided to initiate dialog among members of the PBPK modeling community, as these issues must be overcome for the field of PBPK modeling to advance and for PBPK models to be more routinely applied in support of public health decision-making.


Assuntos
Tomada de Decisões , Modelos Biológicos , Farmacocinética , Saúde Pública , Toxicologia/métodos , Técnicas de Apoio para a Decisão , Órgãos Governamentais , Humanos , Saúde Pública/legislação & jurisprudência , Toxicocinética , Estados Unidos
15.
Food Chem Toxicol ; 112: 375-382, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29331735

RESUMO

Polyfluorinated compounds (PFCs) are authorized for use as greaseproofing agents in food contact paper. As C8-PFCs (8-carbons) are known to accumulate in tissues, shorter-chain C6-PFCs (6-carbons) have replaced C8-PFCs in many food contact applications. However, the potential of C6-PFCs for human biopersistence has not been fully evaluated. For the first time, we provide internal exposure estimates to key metabolites of 6:2 fluorotelomer alcohol (6:2 FTOH), a monomeric component of C6-PFCs, to extend our understanding of exposure beyond estimates of external exposure. Pharmacokinetic data from published rat and human studies on 6:2 FTOH were used to estimate clearance and area under the curve (AUC) for its metabolites: 5:3 fluorotelomer carboxylic acid (5:3 A), perfluorohexanoic acid (PFHxA) and perfluoroheptanoic acid (PFHpA). Internal exposure to 5:3 A was the highest of evaluated metabolites across species and it had the slowest clearance. Additionally, 5:3 A clearance decreased with increasing 6:2 FTOH exposure. Our analysis provides insight into association of increased internal 5:3 A exposure with high biopersistence potential of 6:2 FTOH. Our results identify 5:3 A as an important biomarker of internal 6:2 FTOH exposure for use in biomonitoring studies, and are potentially useful for toxicological assessment of chronic dietary 6:2 FTOH exposure.


Assuntos
Fluorcarbonetos/farmacocinética , Animais , Feminino , Fluorcarbonetos/sangue , Fluorcarbonetos/química , Humanos , Masculino , Estrutura Molecular , Ratos
16.
AIDS Care ; 30(2): 255-265, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-28657333

RESUMO

Sustained retention in HIV medical care is a key health behavior for the long-term health of people living with HIV (PLWH). Approximately 60% of PLWH in the U.S. are poorly retained in HIV care, yet to date, the few available evidence-based retention-promoting interventions are resource and time intensive to implement. The current study describes the feasibility and acceptability of a theory-based retention-promoting intervention designed to meet the needs of a busy clinical care setting. 60 Minutes for Health reflects a low-resource single-session intervention, implemented by a health educator, to PLWH who have had a recent gap in care (≥6-months) in the past 18-months. Intervention content was informed by a situated application of the Information Motivation Behavioral Skills Model and delivered using a Motivational Interviewing-based format. The intervention uses a workbook to guide a series of activities that: (1) Identify and reduce misinformation guiding HIV care attendance. (2) Enhance motivation to maintain care via personal health goals. (3) Build skills for coping with emotional distress related to living with HIV. (4) Increase self-efficacy for navigating the logistics of maintaining care amidst competing priorities. A small feasibility pilot of this intervention protocol was conducted to assess its potential to improve retention in care and to obtain estimates for a larger-scale efficacy trial. Participants were randomized to the 60-minute intervention session (n = 8), or a theory-based time-and-attention control session focused on diet and nutrition (n = 8). Medical records were abstracted to evaluate changes in participants' retention in care status at 12- and 24-months post-intervention. Findings suggest the intervention is both feasible and acceptable to implement with poorly retained PLWH in a clinic setting. Post-intervention a larger proportion of intervention participants were retained in care (12-months: 87.5%, 24-months: 62.5%), compared control participants (12-months: 50.0%, 24-months: 25.0%). Future work should aim to evaluate a larger-scale efficacy trial.


Assuntos
Terapia Comportamental , Infecções por HIV/terapia , Entrevista Motivacional/métodos , Aceitação pelo Paciente de Cuidados de Saúde , Adulto , Estudos de Viabilidade , Feminino , Infecções por HIV/psicologia , Comportamentos Relacionados com a Saúde , Humanos , Masculino , Pessoa de Meia-Idade , Projetos Piloto
17.
Stat Sin ; 28: 1929-1963, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30595637

RESUMO

Missing data are frequently encountered in longitudinal clinical trials. To better monitor and understand the progress over time, one must handle the missing data appropriately and examine whether the missing data mechanism is ignorable or nonignorable. In this article, we develop a new probit model for longitudinal binary response data. It resolves a challenging issue for estimating the variance of the random effects, and substantially improves the convergence and mixing of the Gibbs sampling algorithm. We show that when improper uniform priors are specified for the regression coefficients of the joint multinomial model via a sequence of one-dimensional conditional distributions for the missing data indicators under nonignorable missingness, the joint posterior distribution is improper. A variation of Jeffreys prior is thus established as a remedy for the improper posterior distribution. In addition, an efficient Gibbs sampling algorithm is developed using a collapsing technique. Two model assessment criteria, the deviance information criterion (DIC) and the logarithm of the pseudomarginal likelihood (LPML), are used to guide the choices of prior specifications and to compare the models under different missing data mechanisms. We report on extensive simulations conducted to investigate the empirical performance of the proposed methods. The proposed methodology is further illustrated using data from an HIV prevention clinical trial.

18.
Toxicol Appl Pharmacol ; 330: 9-21, 2017 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-28684146

RESUMO

Manufacturing of perfluorooctanoic acid (PFOA), a synthetic chemical with a long half-life in humans, peaked between 1970 and 2002, and has since diminished. In the United States, PFOA is detected in the blood of >99% of people tested, but serum concentrations have decreased since 1999. Much is known about exposure to PFOA in drinking water; however, the impact of non-drinking water PFOA exposure on serum PFOA concentrations is not well characterized. The objective of this research is to apply physiologically based pharmacokinetic (PBPK) modeling and Monte Carlo analysis to evaluate the impact of historic non-drinking water PFOA exposure on serum PFOA concentrations. In vitro to in vivo extrapolation was utilized to inform descriptions of PFOA transport in the kidney. Monte Carlo simulations were incorporated to evaluate factors that account for the large inter-individual variability of serum PFOA concentrations measured in individuals from North Alabama in 2010 and 2016, and the Mid-Ohio River Valley between 2005 and 2008. Predicted serum PFOA concentrations were within two-fold of experimental data. With incorporation of Monte Carlo simulations, the model successfully tracked the large variability of serum PFOA concentrations measured in populations from the Mid-Ohio River Valley. Simulation of exposure in a population of 45 adults from North Alabama successfully predicted 98% of individual serum PFOA concentrations measured in 2010 and 2016, respectively, when non-drinking water ingestion of PFOA exposure was included. Variation in serum PFOA concentrations may be due to inter-individual variability in the disposition of PFOA and potentially elevated historical non-drinking water exposures.


Assuntos
Caprilatos/farmacocinética , Caprilatos/toxicidade , Exposição Ambiental/efeitos adversos , Fluorcarbonetos/farmacocinética , Fluorcarbonetos/toxicidade , Farmacocinética , Poluentes Químicos da Água/farmacocinética , Poluentes Químicos da Água/toxicidade , Adulto , Alabama , Algoritmos , Animais , Caprilatos/sangue , Simulação por Computador , Fluorcarbonetos/sangue , Meia-Vida , Humanos , Rim/metabolismo , Modelos Biológicos , Método de Monte Carlo , Ohio , Valor Preditivo dos Testes , Ratos , Ratos Wistar , Reprodutibilidade dos Testes , Distribuição Tecidual , Poluentes Químicos da Água/sangue
19.
Environ Int ; 106: 135-143, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28645013

RESUMO

BACKGROUND: Per- and polyfluoroalkyl substances (PFAS) are considered chemicals of emerging concern, in part due to their environmental and biological persistence and the potential for widespread human exposure. In 2007, a PFAS manufacturer near Decatur, Alabama notified the United States Environmental Protection Agency (EPA) it had discharged PFAS into a wastewater treatment plant, resulting in environmental contamination and potential exposures to the local community. OBJECTIVES: To characterize PFAS exposure over time, the Agency for Toxic Substances and Disease Registry (ATSDR) collected blood and urine samples from local residents. METHODS: Eight PFAS were measured in serum in 2010 (n=153). Eleven PFAS were measured in serum, and five PFAS were measured in urine (n=45) from some of the same residents in 2016. Serum concentrations were compared to nationally representative data and change in serum concentration over time was evaluated. Biological half-lives were estimated for perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and perfluorohexane sulfonic acid (PFHxS) using a one-compartment pharmacokinetic model. RESULTS: In 2010 and 2016, geometric mean PFOA and PFOS serum concentrations were elevated in participants compared to the general U.S. POPULATION: In 2016, the geometric mean PFHxS serum concentration was elevated compared to the general U.S. POPULATION: Geometric mean serum concentrations of PFOA, PFOS, and perfluorononanoic acid (PFNA) were significantly (p≤0.0001) lower (49%, 53%, and 58%, respectively) in 2016 compared to 2010. Half-lives for PFOA, PFOS, and PFHxS were estimated to be 3.9, 3.3, and 15.5years, respectively. Concentrations of PFOA in serum and urine were highly correlated (r=0.75) in males. CONCLUSIONS: Serum concentrations of some PFAS are decreasing in this residentially exposed community, but remain elevated compared to the U.S. general population.


Assuntos
Fluorcarbonetos/sangue , Fluorcarbonetos/urina , Poluentes Químicos da Água/sangue , Poluentes Químicos da Água/urina , Adolescente , Adulto , Idoso , Alabama , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
20.
Toxicol Sci ; 158(1): 23-35, 2017 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-28402537

RESUMO

Many physiologically based pharmacokinetic (PBPK) models for environmental chemicals, drugs, and nanomaterials have been developed to aid risk and safety assessments using acslX. However, acslX has been rendered sunset since November 2015. Alternative modeling tools and tutorials are needed for future PBPK applications. This forum article aimed to: (1) demonstrate the performance of 4 PBPK modeling software packages (acslX, Berkeley Madonna, MATLAB, and R language) tested using 2 existing models (oxytetracycline and gold nanoparticles); (2) provide a tutorial of PBPK model code conversion from acslX to Berkeley Madonna, MATLAB, and R language; (3) discuss the advantages and disadvantages of each software package in the implementation of PBPK models in toxicology, and (4) share our perspective about future direction in this field. Simulation results of plasma/tissue concentrations/amounts of oxytetracycline and gold from different models were compared visually and statistically with linear regression analyses. Simulation results from the original models were correlated well with results from the recoded models, with time-concentration/amount curves nearly superimposable and determination coefficients of 0.86-1.00. Step-by-step explanations of the recoding of the models in different software programs are provided in the Supplementary Data. In summary, this article presents a tutorial of PBPK model code conversion for a small molecule and a nanoparticle among 4 software packages, and a performance comparison of these software packages in PBPK model implementation. This tutorial helps beginners learn PBPK modeling, provides suggestions for selecting a suitable tool for future projects, and may lead to the transition from acslX to alternative modeling tools.


Assuntos
Ouro/farmacocinética , Nanopartículas Metálicas/química , Modelos Biológicos , Oxitetraciclina/farmacocinética , Animais , Cães , Ouro/sangue , Ouro/química , Oxitetraciclina/sangue , Suínos , Distribuição Tecidual
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA