Population Pharmacokinetics of Morphine in Patients With Nonalcoholic Steatohepatitis (NASH) and Healthy Adults

Nonalcoholic steatohepatitis increases plasma retention of sorafenib-glucuronide in a mouse model by altering hepatocyte hopping

Hepatocyte hopping is the hepatocyte-to-sinusoid-to-hepatocyte shuttling that increases the efficiency of hepatic elimination of xenobiotics. This phenomenon is mediated via efflux of hepatic metabolites by Mrp3 and reuptake by Oatp transporters in sequential hepatocytes until eventual biliary efflux by Mrp2. Sorafenib-glucuronide (SFB-G), the major metabolite of sorafenib (SFB), undergoes hepatocyte hopping, leading to efficient biliary elimination. Nonalcoholic steatohepatitis (NASH) alters the functioning of transporters involved in hepatocyte hopping. The purpose of this study was to quantify the effect of NASH on the three drug disposition processes of hepatocyte hopping. Male FVB and C57BL/6 wild-type (WT), Oatp1a/1b cluster knockout (O-/-), and Mrp2 knockout (Mrp2 -/-) mice were fed a methionine and choline deficient (MCD) diet to induce NASH. Mice were administered 10 mg/kg SFB via oral gavage and concentrations of SFB and SFB-G in plasma quantified using liquid-chromatography tandem mass spectrometry. Compared to WT, plasma area under the concentration-time curve (AUC) of SFB-G increased by 108-fold in the O-/--C group and by 345-fold in the Mrp2 -/--C group. In the WT-NASH group, up-regulation of Mrp3 and decreased Mrp2 function, along with reduced Oatp uptake, elevated SFB-G AUC by 165-fold. SFB-G AUC in the O-/--NASH group increased by 108-fold compared to WT-C (3.2-fold compared to O-/--C). SFB-G AUC in the Mrp2 -/--NASH group increased by 450-fold (1.2-fold compared to Mrp2-/--C). Taken together, the mislocalization of Mrp2 in NASH is a major contributor to the decrease in SFB-G biliary efflux, but decreased Oatp uptake and enhanced sinusoidal efflux also limit the contribution of downstream hepatocytes, resulting in plasma retention that recapitulates the altered pharmacokinetics observed in human NASH.

Physiologically Based Pharmacokinetic (PBPK) Model Predictions of Disease Mediated Changes in Drug Disposition in Patients with Nonalcoholic Fatty Liver Disease (NAFLD)

PURPOSE

This study was designed to verify a virtual population representing patients with nonalcoholic fatty liver disease (NAFLD) to support the implementation of a physiologically based pharmacokinetic (PBPK) modeling approach for prediction of disease-related changes in drug pharmacokinetics.

METHODS

A virtual NAFLD patient population was developed in GastroPlus (v.9.8.2) by accounting for pathophysiological changes associated with the disease and proteomics-informed alterations in the abundance of metabolizing enzymes and transporters pertinent to drug disposition. The NAFLD population model was verified using exemplar drugs where elimination is influenced predominantly by cytochrome P450 (CYP) enzymes (chlorzoxazone, caffeine, midazolam, pioglitazone) or by transporters (rosuvastatin, 11C-metformin, morphine and the glucuronide metabolite of morphine).

RESULTS

PBPK model predictions of plasma concentrations of all the selected drugs and hepatic radioactivity levels of 11C-metformin were consistent with the clinically-observed data. Importantly, the PBPK simulations using the virtual NAFLD population model provided reliable estimates of the extent of changes in key pharmacokinetic parameters for the exemplar drugs, with mean predicted ratios (NAFLD patients divided by healthy individuals) within 0.80- to 1.25-fold of the clinically-reported values, except for midazolam (prediction-fold difference of 0.72).

CONCLUSION

A virtual NAFLD population model within the PBPK framework was successfully developed with good predictive capability of estimating disease-related changes in drug pharmacokinetics. This supports the use of a PBPK modeling approach for prediction of the pharmacokinetics of new investigational or repurposed drugs in patients with NAFLD and may help inform dose adjustments for drugs commonly used to treat comorbidities in this patient population.

Characterizing Pharmacokinetics in Children With Obesity-Physiological, Drug, Patient, and Methodological Considerations

Childhood obesity is an alarming public health problem. The pediatric obesity rate has quadrupled in the past 30 years, and currently nearly 20% of United States children and 9% of children worldwide are classified as obese. Drug distribution and elimination processes, which determine drug exposure (and thus dosing), can vary significantly between patients with and without obesity. Obesity-related physiological changes, such as increased tissue volume and perfusion, altered blood protein concentrations, and tissue composition can greatly affect a drug's volume of distribution, which might necessitate adjustment in loading doses. Obesity-related changes in the drug eliminating organs, such as altered enzyme activity in the liver and glomerular filtration rate, can affect the rate of drug elimination, which may warrant an adjustment in the maintenance dosing rate. Although weight-based dosing (i.e., in mg/kg) is commonly practiced in pediatrics, choice of the right body size metric (e.g., total body weight, lean body weight, body surface area, etc.) for dosing children with obesity still remains a question. To address this gap, the interplay between obesity-related physiological changes (e.g., altered organ size, composition, and function), and drug-specific properties (e.g., lipophilicity and elimination pathway) needs to be characterized in a quantitative framework. Additionally, methodological considerations, such as adequate sample size and optimal sampling scheme, should also be considered to ensure accurate and precise top-down covariate selection, particularly when designing opportunistic studies in pediatric drug development. Further factors affecting dosing, including existing dosing recommendations, target therapeutic ranges, dose capping, and formulations constraints, are also important to consider when undergoing dose selection for children with obesity. Opportunities to bridge the dosing knowledge gap in children with obesity include modeling and simulating techniques (i.e., population pharmacokinetic and physiologically-based pharmacokinetic [PBPK] modeling), opportunistic clinical data, and real world data. In this review, key considerations related to physiology, drug parameters, patient factors, and methodology that need to be accounted for while studying the influence of obesity on pharmacokinetics in children are highlighted and discussed. Future studies will need to leverage these modeling opportunities to better describe drug exposure in children with obesity as the childhood obesity epidemic continues.

Development and Evaluation of a Virtual Population of Children with Obesity for Physiologically Based Pharmacokinetic Modeling

BACKGROUND AND OBJECTIVE

While one in five children in the USA are now obese, and more than three-quarters receive at least one drug during childhood, there is limited dosing guidance for this vulnerable patient population. Physiologically based pharmacokinetic modeling can bridge the gap in the understanding of how pharmacokinetics, including drug distribution and clearance, changes with obesity by incorporating known obesity-related physiological changes in children. The objective of this study was to develop a virtual population of children with obesity to enable physiologically based pharmacokinetic modeling, then use the novel virtual population in conjunction with previously developed models of clindamycin and trimethoprim/sulfamethoxazole to better understand dosing of these drugs in children with obesity.

METHODS

To enable physiologically based pharmacokinetic modeling, a virtual population of children with obesity was developed using national survey, electronic health record, and clinical trial data, as well as data extracted from the literature. The virtual population accounts for key obesity-related changes in physiology relevant to pharmacokinetics, including increased body size, body composition, organ size and blood flow, plasma protein concentrations, and glomerular filtration rate. The virtual population was then used to predict the pharmacokinetics of clindamycin and trimethoprim/sulfamethoxazole in children with obesity using previously developed physiologically based pharmacokinetic models.

RESULTS

Model simulations predicted observed concentrations well, with an overall average fold error of 1.09, 1.24, and 1.53 for clindamycin, trimethoprim, and sulfamethoxazole, respectively. Relative to children without obesity, children with obesity experienced decreased clindamycin and trimethoprim/sulfamethoxazole weight-normalized clearance and volume of distribution, and higher absolute doses under recommended pediatric weight-based dosing regimens.

CONCLUSIONS

Model simulations support current recommended weight-based dosing in children with obesity for clindamycin and trimethoprim/sulfamethoxazole, as they met target exposure despite these changes in clearance and volume of distribution.

Contemporary Trends in Hospitalizations for Comorbid Chronic Liver Disease and Substance Use Disorders

INTRODUCTION

Chronic liver diseases (CLDs) and substance use disorders (SUDs) are increasingly prevalent and often coexist. Contemporary studies describing the characteristics and hospitalization trends of those with comorbid CLD-SUD are lacking. We aimed to characterize a population-based cohort with comorbid CLD-SUD and describe trends in these hospitalizations over time by individual-level characteristics.

METHODS

We performed a cross-sectional analysis of the National Inpatient Sample from 2005 through 2017. Diagnosis codes were used to identify adult hospitalizations with CLD, SUD, or both. Bivariate and multivariate analyses were used to make comparisons between diagnosis categories. Unadjusted and age-adjusted trends in these hospitalizations were described over time.

RESULTS

Of 401,867,749 adult hospital discharges, 3.2% had CLD-only and 1.7% had comorbid CLD-SUD. Compared with CLD-only, comorbid CLD-SUD hospitalizations resulted in higher inpatient mortality (3.1% vs 2.4%, P < 0.001) and were associated with younger age, male sex, Native American race, and urban and Western US location. Over time, comorbid hospitalizations grew 34%, and the demographics shifted with larger increases in hospitalization rates seen in younger individuals, women, Native Americans, and those publicly insured. In comorbid hospitalizations, alcoholic SUD and CLD decreased, but drug SUDs and nonalcoholic fatty liver diseases are fast-growing contributors.

DISCUSSION

In this comprehensive analysis of US hospitalizations, comorbid CLD-SUD hospitalizations are increasing over time and lead to higher inpatient mortality than CLD alone. We further characterize the changing demographics of these hospitalizations, providing a contemporary yet inclusive look at comorbid CLD-SUD hospitalizations. These data can guide interventions needed to improve the poor outcomes suffered by this growing population.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Asking the Right Questions With Animal Models: Methionine- and Choline-Deficient Model in Predicting Adverse Drug Reactions in Human NASH

In the past few decades, great conceptual and technological advances have been made in the field of toxicology, but animal model-based research still remains one of the most widely used and readily available tools for furthering our current knowledge. However, animal models are not perfect in predicting all systemic toxicity in humans. Extrapolating animal data to accurately predict human toxicities remains a challenge, and researchers are obligated to question the appropriateness of their chosen animal model. This paper provides an assessment of the utility of the methionine- and choline-deficient (MCD) diet fed animal model in reflecting human nonalcoholic steatohepatitis (NASH) and the potential risks of adverse drug reactions and toxicities that are associated with the disease. As a commonly used NASH model, the MCD model fails to exhibit most metabolic abnormalities in a similar manner to the human disease. The MCD model, on the other hand, closely resembles human NASH histology and reflects signatures of drug transporter alterations in humans. Due to the nature of the MCD model, it should be avoided in studies of NASH pathogenesis, metabolic parameter evaluation, and biomarker identification. But it can be used to accurately predict altered drug disposition due to NASH-associated transporter alterations.