Renal Function Descriptors in Neonates: Which Creatinine-Based Formula Best Describes Vancomycin Clearance?

Population Pharmacokinetic Analysis and Dose Regimen Optimization in Japanese Infants with an Extremely Low Birth Weight

Vancomycin is a synthetic antibiotic effective against Gram-positive pathogens. Although the clinical applicability of vancomycin for infants has been increasing, the pharmacokinetic data for vancomycin in extremely low-birth-weight infants are limited. The aim of this study was to construct a population pharmacokinetics model for vancomycin in extremely-low-birth-weight infants and establish an optimal dosage regimen. We enrolled children aged less than 1 year with a birth weight of less than 1,000 g and body weight at vancomycin prescription of less than 1,500 g. Pharmacokinetic data from 19 patients were analyzed, and a population pharmacokinetics model was developed using nonlinear mixed-effects modeling software. Goodness-of-fit plots, a nonparametric bootstrap analysis, and a prediction-corrected visual predictive check were employed to evaluate the final model. The dosage regimen was optimized based on the final model. The pharmacokinetic data fit a one-compartment model with first-order elimination, and body weight and estimated serum creatinine level were used as significant covariates. In a simulation using the final model, the optimal dosage regimen, especially when the serum creatinine level (>0.6 mg/dl) was high, was 5.0 to 7.5 mg/kg of body weight twice a day every 12 h; this was required to reduce the dosage compared with that in previous studies. The recommended doses based on the current target time course concentration curves may not be appropriate for extremely-low-birth-weight infants.

Population Pharmacokinetics and Pharmacodynamics of Norvancomycin in Children With Malignant Hematological Disease

Knowledge of pharmacokinetic (PK) behavior of norvancomycin (NVCM) in pediatric patients is lacking, which leads to empirical therapy in clinical practice. This study developed a population PK model of children aged 0-15 years; 112 opportunistic samples in total from 90 children were analyzed. The stability and prediction of the final model were evaluated by goodness-of-fit plots, nonparametric bootstrap, visual predictive check, and normalized prediction distribution errors. The PKs of NVCM in children was described by a 2-compartment model with first-order elimination along with body weight and estimated glomerular filtration rate as significant covariates on clearance. The population typical values of the PK parameters were as follows: clearance 0.12 L/kg/h, central compartment distribution volume 0.17 L/kg, peripheral compartment distribution volume 0.38 L/kg, and intercompartmental clearance 0.35 L/kg/h. Logistic analysis showed that the ratio of area under the concentration-time curve over 24 hours (AUC_0-24 ) to minimum inhibitory concentration (MIC) had the strongest correlation with clinical efficacy, and at least 80% clinical efficiency could be achieved when AUC_0-24 /MIC ≥ 221.06 was defined as the target. Monte Carlo simulation results suggested that a higher dose was required for this pediatric population in order to reach the target. The dosing regimen was optimized based on the final model. A population PK model of NVCM was first characterized in children with hematologic malignancy, and an evidence-based approach for NVCM dosage individualization was provided.

A population pharmacokinetic model for individualised dosage regimens of vancomycin in Chinese neonates and young infants

Population pharmacokinetic (PPK) modelling is an easy and impartment method for estimating drug concentration for use inindividualized therapy, especially for young patients and to help protect drug-induced diseases. The purpose of this study was to develop a PPK model for effective dosing of vancomycin in Chinese neonates and young infants. The PPK modelling tool Phoenix^® NLME^™ was use to assess demographic and routine clinical pharmacokinetic (PK) data retrospectively collected for patients admitted to Children's Hospital of Chongqing Medical University between 2011 and 2016. Data of patients admitted to the hospital between January and June of 2017 were used in validation study, and the final model was also preliminary validated in 2 cases in another hospital. A total of 421 serum samples from 316 patients were included in the initial PPK analysis. A two-compartment PPK model was developed, and exponential-error model was used to describe inter-individual variability of clearance. Residual variability was described by an additive model. The final PPK model was demonstrated as valid by internal and external model evaluation. Of note, the clearance and volume of vancomycin in Chinese neonates and young infants may be greater than in Caucasians. Herein, we describe the establishment of an accurate PPK model of vancomycin for Chinese neonates and young infants, which may be useful as a dosing algorithm for this particular paediatric population.

Quantitative clinical pharmacology practice for optimal use of antibiotics during the neonatal period

INTRODUCTION

For safe and effective neonatal antibiotic therapy, knowledge of the pharmacokinetic parameters of antibacterial agents in neonates is a prerequisite. Fast maturational changes during the neonatal period influence pharmacokinetic and pharmacodynamic parameters and their variability. Consequently, the need for applying quantitative clinical pharmacology and determining optimal drug dosing regimens in neonates has become increasingly recognized.

AREAS COVERED

Modern quantitative approaches, such as pharmacometrics, are increasingly utilized to characterize, understand and predict the pharmacokinetics of a drug and its effect, and to quantify the variability in the neonatal population. Individual factors, called covariates in modeling, are integrated in such approaches to explain inter-individual pharmacokinetic variability. Pharmacometrics has been shown to be a relevant tool to evaluate, optimize and individualize drug dosing regimens.

EXPERT OPINION

Challenges for optimal use of antibiotics in neonates can largely be overcome with quantitative clinical pharmacology practice. Clinicians should be aware that there is a next step to support the clinical decision-making based on clinical characteristics and therapeutic drug monitoring, through Bayesian-based modeling and simulation methods. Pharmacometric modeling and simulation approaches permit us to characterize population average, inter-subject and intra-subject variability of pharmacokinetic parameters such as clearance and volume of distribution, and to identify and quantify key factors that influence the pharmacokinetic behavior of antibiotics during the neonatal period.