A Survey of Neonatal Pharmacokinetic and Pharmacodynamic Studies in Pediatric Drug Development

Gaps in Accessibility of Pediatric Formulations: A Cross-Sectional Observational Study of a Teaching Hospital in Northern Thailand

The lack of appropriate medicines for children has a significant impact on health care practices in various countries around the world, including Thailand. The unavailability of pediatric medicines in hospital formularies causes issues regarding off-label use and extemporaneous preparation, resulting in safety and quality risks relating to the use of medicines among children. This research aimed to identify missing pediatric formulations based on the experience of healthcare professionals in a teaching hospital in northern Thailand. A cross-sectional survey was conducted to collect data on missing pediatric formulations, the reasons for their inaccessibility, their off-label uses, their reactions to the situation, and suggestions to improve access to these identified medications. The survey was distributed to all physicians, nurses, and pharmacists involved in prescribing, preparing, dispensing, and administering pediatric medicines. A total of 218 subjects responded to the survey. Omeprazole, sildenafil, and spironolactone suspension were most often identified as missing formulations for children by physicians and pharmacists. They are unavailable on the Thai market or in any hospital formulary. For nurses, sodium bicarbonate, potassium chloride, and chloral hydrate were the most problematic formulations in terms of preparation, acceptability, and administration. These medicines were difficult to swallow because of their taste or texture.

Bioinformatics and Computer Simulation approaches to the discovery and analysis of Bioactive Peptides

The traditional process of separating and purifying bioactive peptides is laborious and time-consuming. Using a traditional process to identify is difficult, and there is a lack of fast and accurate activity evaluation methods. How to extract bioactive peptides quickly and efficiently is still the focus of bioactive peptides research. In order to improve the present situation of the research, bioinformatics techniques and peptidome methods are widely used in this field. At the same time, bioactive peptides have their own specific pharmacokinetic characteristics, so computer simulation methods have incomparable advantages in studying the pharmacokinetics and pharmacokinetic-pharmacodynamic correlation models of bioactive peptides. The purpose of this review is to summarize the combined applications of bioinformatics and computer simulation methods in the study of bioactive peptides, with focuses on the role of bioinformatics in simulating the selection of enzymatic hydrolysis and precursor proteins, activity prediction, molecular docking, physicochemical properties, and molecular dynamics. Our review shows that new bioactive peptide molecular sequences with high activity can be obtained by computer-aided design. The significance of the pharmacokinetic-pharmacodynamic correlation model in the study of bioactive peptides is emphasized. Finally, some problems and future development potential of bioactive peptides binding new technologies are prospected.

Model-Informed Pediatric Drug Development: Application of Pharmacometrics to Define the Right Dose for Children

One of the biggest challenges in pediatric drug development is defining a safe and effective dose in pediatric populations, which span across a wide age and development range from neonates to adolescents. Model-informed drug development approaches are particularly suited to address knowledge gaps including data leveraging to increase the success of pediatric studies. Considering the often limited number of patients available for study and logistic difficulties to collect the necessary data in pediatric populations, the application of pharmacometrics and modeling and simulation techniques can improve clinical trial efficiency, increase the probability of regulatory success, and optimize therapeutic individualization in support of dedicated trials. This review describes the state of pediatric model-informed drug development to define the right dose for children and provides suggestions for future development.

Premature birth: topics in physiology and pharmacological characteristics

OBJECTIVE

To review the main physiological and pharmacological changes related to prematurity, to promote the evidence-based clinical practice.

METHODS

This is a narrative review whose research was carried out in the ScienceDirect and Medline databases via PubMed, searching for articles in any language from January 2000 to February 2020.

RESULTS

Premature newborns are born before completing the maturation process that prepares them for extrauterine life, which occurs especially in the last weeks of pregnancy. Therefore, they have their own characteristics in development. Several physiological peculiarities stand out, such as disturbances in glucose regulation, adrenal function, thermoregulation, immunity, in addition to changes in liver, renal and respiratory functions. Pharmacological aspects were also highlighted, involving pharmacokinetics and pharmacodynamics.

CONCLUSIONS

Despite the recent advances in prematurity, it is still an area with many uncertainties, since several changes occur quickly and there are ethical issues that make studies difficult. Thus, it is clear that the therapeutic management of premature infants is still very much based on clinical practice.

Pediatric formulation development - Challenges of today and strategies for tomorrow: Summary report from M-CERSI workshop 2019

A workshop on "Pediatric Formulation Development: Challenges of Today and Strategies for Tomorrow" was organized jointly by the University of Maryland's Center of Excellence in Regulatory Science and Innovation (M-CERSI), the U.S. Food and Drug Administration (FDA) and the International Consortium for Innovation and Quality in Pharmaceutical Development (IQ) Drug Product Pediatric Working Group (PWG). This multi-disciplinary, pediatric focused workshop was held over a two-day period (18-19 Jun 2019) and consisted of participants from industry, regulatory agencies, academia and other organizations from both US and Europe. The workshop consisted of sequential sessions on formulation, analytical, clinical, and regulatory and industry lessons learned and future landscape. Each session began with a series of short framing presentations, followed by facilitated breakout sessions and panel discussion. The formulation session was dedicated to three main topics pertaining to drug product acceptability, excipients in pediatrics and oral administration device considerations. The analytical session discussed key considerations for dosing vehicle selection and analytical strategies for testing of different dosage forms, specifically mini-tablets (multiparticulates). The clinical session highlighted the influence of pediatric pharmacokinetics prediction on formulation design, pediatric drug development strategies and clinical considerations to support pediatric formulation design. The regulatory and industry lessons learned and future landscape session explored the regional differences that exist in regulatory expectations, requirements for pediatric formulation development, and key patient-centric factors to consider when developing novel pediatric formulations. This session also discussed potential collaboration opportunities and tools for pediatric formulation development. This manuscript summarizes the key discussions and outcomes of all the sessions in the workshop with a broadened review and discussion of the topics that were covered.

Clinical pharmacology and dosing regimen optimization of neonatal opioid withdrawal syndrome treatments

In this paper, we review the management of neonatal opioid withdrawal syndrome (NOWS) and clinical pharmacology of primary treatment agents in NOWS, including morphine, methadone, buprenorphine, clonidine, and phenobarbital. Pharmacologic treatment strategies in NOWS have been mostly empirical, and heterogeneity in dosing regimens adds to the difficulty of extrapolating study results to broader patient populations. As population pharmacokinetics (PKs) of pharmacologic agents in NOWS become more well‐defined and knowledge of patient‐specific factors affecting treatment outcomes continue to accumulate, PK/pharmacodynamic modeling and simulation will be powerful tools to aid the design of optimal dosing regimens at the patient level. Although there is an increasing number of clinical trials on the comparative efficacy of treatment agents in NOWS, here, we also draw attention to the importance of optimizing the dosing regimen, which can be arguably equally important at identifying the optimal treatment agent.

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.

Physiologically Based Pharmacokinetic Modeling Framework to Predict Neonatal Pharmacokinetics of Transplacentally Acquired Emtricitabine, Dolutegravir, and Raltegravir

BACKGROUND AND OBJECTIVE

Little is understood about neonatal pharmacokinetics immediately after delivery and during the first days of life following intrauterine exposure to maternal medications. Our objective was to develop and evaluate a novel, physiologically based pharmacokinetic modeling workflow for predicting perinatal and postnatal disposition of commonly used antiretroviral drugs administered prenatally to pregnant women living with human immunodeficiency virus.

METHODS

Using previously published, maternal-fetal, physiologically based pharmacokinetic models for emtricitabine, dolutegravir, and raltegravir built with PK-Sim/MoBi^®, placental drug transfer was predicted in late pregnancy. The total drug amount in fetal compartments at term delivery was estimated and subsequently integrated as initial conditions in different tissues of a whole-body, neonatal, physiologically based pharmacokinetic model to predict drug concentrations in the neonatal elimination phase after birth. Neonatal elimination processes were parameterized according to published data. Model performance was assessed by clinical data.

RESULTS

Neonatal physiologically based pharmacokinetic models generally captured the initial plasma concentrations after delivery but underestimated concentrations in the terminal phase. The mean percentage error for predicted plasma concentrations was - 71.5%, - 33.8%, and 76.7% for emtricitabine, dolutegravir, and raltegravir, respectively. A sensitivity analysis suggested that the activity of organic cation transporter 2 and uridine diphosphate glucuronosyltransferase 1A1 during the first postnatal days in term newborns is ~11% and ~30% of that in adults, respectively.

CONCLUSIONS

These findings demonstrate the general feasibility of applying physiologically based pharmacokinetic models to predict washout concentrations of transplacentally acquired drugs in newborns. These models can increase the understanding of pharmacokinetics during the first postnatal days and allow the prediction of drug exposure in this vulnerable population.

Opioid Treatment for Neonatal Opioid Withdrawal Syndrome: Current Challenges and Future Approaches

Chronic intrauterine exposure to psychoactive drugs often results in neonatal opioid withdrawal syndrome (NOWS). When nonpharmacologic measures are insufficient in controlling NOWS, morphine, methadone, and buprenorphine are first-line medications commonly used to treat infants with NOWS because of in utero exposure to opioids. Research suggests that buprenorphine may be the leading drug therapy used to treat NOWS when compared with morphine and methadone. Currently, there are no consensus or standardized treatment guidelines for medications prescribed for NOWS. Opioids used to treat NOWS exhibit large interpatient variability in pharmacokinetics (PK) and pharmacodynamic (PD) response in neonates. Organ systems undergo rapid maturation after birth that may alter drug disposition and exposure for any given dose during development. Data regarding the PK and PD of opioids in neonates are sparse. Pharmacometric methods such as physiologically based pharmacokinetic and population pharmacokinetic modeling can be used to explore factors predictive of some of the variability associated with the PK/PD of opioids in newborns. This review discusses the utility of pharmacometric techniques for enhancing precision dosing in infants requiring opioid treatment for NOWS. Applying these approaches may contribute to optimizing the outcome by reducing cumulative drug exposure, mitigating adverse drug effects, and reducing the burden of NOWS in neonates.

USE OF OFF-LABEL MEDICATIONS IN A NEONATAL INTENSIVE CARE UNIT

Objective:

This paper aims to analyze the use of off label (OL) medicines, according to the National Regulatory Agency, in a neonatal intensive care unit of a high-risk maternity hospital in Northeast Brazil.

Methods:

A cross-sectional study was carried out, using a convenience sample of newborns that used mechanical ventilation at the Intensive Care Unit. As a reference, OL medications were considered for those without an approval for newborn usage by the Brazilian Health Regulatory Agency (Agência Nacional de Vigilância Sanitária - ANVISA) and by the Food and Drugs Administration (FDA).

Results:

The sample consisted of 158 newborns, 58.3% male, 87.7% premature, and 70.2% of low or very low birth weight. According to ANVISA, 440 out of the 1,167 prescriptions analyzed were OL, with 98.1% of newborns exposed to at least one of these drugs. According to the FDA, 484 prescriptions were OL, with 75.8% of newborns exposed to at least one of them. Anti-infectives were the most prescribed OL medications. Neonates who presented respiratory failure and pneumonia used these drugs more often; and there was no relation between their use and the number of deaths.

Conclusions:

Nearly all newborns at the Intensive Care Units, mainly preterm infants, are exposed to at least one off-label (OL) medication during hospital stay, according to the national and international regulatory agencies. No association was found between off-label prescriptions and the frequency of complications or neonatal deaths.

Developmental Pharmacodynamics and Modeling in Pediatric Drug Development

Challenges in pediatric drug development include small patient numbers, limited outcomes research, ethical barriers, and sparse biosamples. Increasingly, pediatric drug development is focusing on extrapolation: leveraging knowledge about adult disease and drug responses to inform projections of drug and clinical trial performance in pediatric subpopulations. Pharmacokinetic-pharmacodynamic (PK-PD) modeling and extrapolation aim to reduce the numbers of patients and data points needed to establish efficacy. Planning for PK-PD and biomarker studies should begin early in the adult drug development program. Extrapolation relies on the assumption that both the underlying disease and the mechanism of action of the drug used to treat that disease are similar in adults and pediatric subpopulations. Clearly, developmental changes in PK and PD need to be considered to enhance the quality of PK-PD modeling and, therefore, increase the success of extrapolation. This article focuses on the influence of differences in PD between adults and pediatric subpopulations that are highly relevant for the use of extrapolation.

Administración y preparación de antimicrobianos en una unidad chilena de cuidados neonatales

Objetivo: Describir la preparación, administración y monitorización de los antimicrobianos utilizados en una Unidad de Cuidados Neonatales en Santiago de Chile. Métodos: Estudio descriptivo. Se realizó la aplicación de un instrumento a 20 matronas de neonatología de una Unidad Chilena de Cuidados Neonatales (UCHCN) en 2018, para recopilar información respecto a once variables en la preparación y administración de antimicrobianos. El estudio abarcó tres variables principales: preparación, mantención y monitorización de los antimicrobianos. Resultados: Se recopiló información de 14 antimicrobianos, de los cuales la presentación del 92.8% de ellos era inyectable y el 78.2% de los encuestados reconocía el valor de la unidad de dosificación del medicamento. Mantención 85.7% de los antimicrobianos son eliminados luego de su preparación. Para dilución se utiliza mayormente la solución fisiológica en un 76.9% de los casos y el volumen utilizado de diluyente y concentración final varió según cada medicamento. Un 92.8% de los antimicrobianos se administra por vía endovenosa y todos a través de una bomba de jeringa. Monitorización específica de la administración sólo se realiza en un 7.2% de ellos. Conclusiones: Debido a las variabilidades encontradas en los procesos de mantención, dilución y monitorización es que se propone la creación o el mejoramiento y difusión de protocolos locales, para evitar efectos adversos o complicaciones y así resguardar la seguridad de los pacientes.

Neonatal pharmacology and clinical implications

During the neonatal period, there is physiological immaturity of organs, systems and metabolic pathways that influences the pharmacokinetics and pharmacodynamics of administered drugs, the dosage of which should be constantly amended, considering the progressive increase in weight and the maturation of the elimination pathways. In this article, we analyse the main pharmacokinetic aspects (absorption, distribution, metabolism and excretion) that exist during the neonatal period, to offer a description of the physiological background for variability in pharmacological dosing.

Dose rationale and pharmacokinetics of dexmedetomidine in mechanically ventilated new-borns: impact of design optimisation

PURPOSE

There is a need for alternative analgosedatives such as dexmedetomidine in neonates. Given the ethical and practical difficulties, protocol design for clinical trials in neonates should be carefully considered before implementation. Our objective was to identify a protocol design suitable for subsequent evaluation of the dosing requirements for dexmedetomidine in mechanically ventilated neonates.

METHODS

A published paediatric pharmacokinetic model was used to derive the dosing regimen for dexmedetomidine in a first-in-neonate study. Optimality criteria were applied to optimise the blood sampling schedule. The impact of sampling schedule optimisation on model parameter estimation was assessed by simulation and re-estimation procedures for different simulation scenarios. The optimised schedule was then implemented in a neonatal pilot study.

RESULTS

Parameter estimates were more precise and similarly accurate in the optimised scenarios, as compared to empirical sampling (normalised root mean square error: 1673.1% vs. 13,229.4% and relative error: 46.4% vs. 9.1%). Most importantly, protocol deviations from the optimal design still allowed reasonable parameter estimation. Data analysis from the pilot group (n = 6) confirmed the adequacy of the optimised trial protocol. Dexmedetomidine pharmacokinetics in term neonates was scaled using allometry and maturation, but results showed a 20% higher clearance in this population compared to initial estimates obtained by extrapolation from a slightly older paediatric population. Clearance for a typical neonate, with a post-menstrual age (PMA) of 40 weeks and weight 3.4 kg, was 2.92 L/h. Extension of the study with 11 additional subjects showed a further increased clearance in pre-term subjects with lower PMA.

CONCLUSIONS

The use of optimal design in conjunction with simulation scenarios improved the accuracy and precision of the estimates of the parameters of interest, taking into account protocol deviations, which are often unavoidable in this event-prone population.

Impact of Regulatory Incentive Programs on the Future of Pediatric Drug Development

Surveys evaluating industry experience with performing pediatric studies under the Best Pharmaceutical for Children Act (BPCA) and Pediatric Research Equity Act (PREA) regulatory regime were conducted by Tufts Center for the Study of Drug Development (Tufts CSDD) in 2000, 2006, and 2016. These survey results are being used to assess the future impact of regulatory incentive programs on generating pediatric specific labeling information and development of age-appropriate drug formulations. A second perspective will be provided through the experience and expertise of neonatal/pediatric clinicians and researchers with a focus on the urgent need for the study of new and existing drugs in this vulnerable population (especially with 90% of drugs in neonates still being used off-label). This group will also address the impact of existing regulations and the likely trajectory of future pediatric drug development efforts after nearly 2 decades of regulatory incentives (both mandatory and voluntary). Finally, this review will provide input on approaches that are needed to continue to advance pediatric drug development with an emphasis on rare diseases.

Renal Clearance in Newborns and Infants: Predictive Performance of Population-Based Modeling for Drug Development

The objective of this study was to evaluate the predictive performance of population models to predict renal clearance in newborns and infants. Pharmacokinetic (PK) data from eight drugs in 788 newborns and infants were used to evaluate the predictive performance of the population models based on postmenstrual age (PMA), postnatal age, gestational age, and body weight. For the PMA model, the average fold error for clearance (CL)_predicted /CL_observed was within a twofold range for each drug in all subgroups. For drugs with > 90% renal elimination, the prediction bias ranged from 0.7-1.3. For drugs with 60-80% renal elimination, the prediction bias ranged 0.6-2.0. Our results suggest that PMA-based sigmoidal maximum effect (E_max ) model, in combination with bodyweight-based scaling and kidney function assessment, can be used in population PK (PopPK) modeling for drugs that are primarily eliminated via renal pathway to inform initial dose selection for newborns and infants with normal renal function in clinical trials.

Physiologically Based Pharmacokinetic Prediction of Linezolid and Emtricitabine in Neonates and Infants

INTRODUCTION

Modeling and simulation approaches are increasingly being utilized in pediatric drug development. Physiologically based pharmacokinetic (PBPK) modeling offers an enhanced ability to predict age-related changes in pharmacokinetics in the pediatric population.

METHODS

In the current study, adult PBPK models were developed for the renally excreted drugs linezolid and emtricitabine. PBPK models were then utilized to predict pharmacokinetics in pediatric patients for various age groups from the oldest to the youngest patients in a stepwise approach.

RESULTS

Pharmacokinetic predictions for these two drugs in the pediatric population, including infants and neonates, were within a twofold range of clinical observations. Based on this study, linezolid and emtricitabine pediatric PBPK models incorporating the ontogeny in renal maturation describe the pharmacokinetic differences between adult and pediatric populations, even though the contribution of renal clearance to the total clearance of two drugs was very different (30 % for linezolid vs. 86 % for emtricitabine).

CONCLUSION

These results suggest that PBPK modeling may provide one option to help predict the pharmacokinetics of renally excreted drugs in neonates and infants.

Disease burden-research match? Registered trials in child health from low- and middle-income and high-income countries

AIM

The aim of this study was to determine whether there is a match between the health problems that children face and the clinical trials that are being conducted, especially in low- and middle-income countries (LMICs).

METHODS

All trials on the World Health Organisation International Clinical Trials Registry Platform registered from 2005 to 2013 were reviewed. The disease-specific focus of registered trials for children was compared to the global burden of disease for 2011 using World Health Organisation disability-adjusted life-year data.

RESULTS

Children account for 34% of the global disease burden, but were represented in only 15% (29 899/203 726) of registered trials. Although the number of trials in children registered annually has increased over time (from 3174 in 2005 to 3392 in 2013), the proportion of trials involving children has decreased (from 18 to 13%). LMICs account for 98% of the disease burden among children world-wide, but only 22% of trials. More trials were registered in high-income countries than in LMICs for the majority of the disease categories. There was moderate correlation between the number of trials and the burden of each disease within each region (Spearman's correlation r = 0.6, P = 0.007 and r = 0.55, P = 0.02 in LMICs and high-income countries, respectively).

CONCLUSION

Overall, children continue to be under-represented in clinical trials, particularly children from LMICs where disease burden is greatest. Clinical trial activity correlates moderately with disease burden among the world's children. A more evidence-informed approach for prioritising trials to specifically address the health-care needs of children is required.

Challenges and opportunities to enhance global drug development in neonates

PURPOSE OF REVIEW

This study reviews the history of neonatal drug development, recent legislative efforts designed to facilitate the study of therapeutic agents in neonates, and future steps necessary to advance drug development.

RECENT FINDINGS

Although many federal regulations have been introduced over the past 15 years to encourage pediatric and neonatal drug development, the majority of medications that are used in the Neonatal Intensive Care Unit are not approved by the Food and Drug Administration (FDA) for use in neonates. There are many challenges that investigators encounter in conducting neonatal clinical trials. The Critical Path Institute working in conjunction with the FDA has developed several consortia, including the International Neonatal Consortium and Pediatric Trials Consortium, to address these concerns and facilitate interactions of researchers, regulators, funding agencies, industry, and others across the globe to produce regulatory ready and high quality data for neonatal therapeutics.

SUMMARY

Neonatal drug development is an area which deserves significant attention if we hope to continue to improve outcomes. With the help of international collaborations, it is possible to accelerate efficient and high quality neonatal research through multidisciplinary teams that share data, knowledge, and expertise to advance medical innovation and regulatory science.

Drug versus placebo randomized controlled trials in neonates: A review of ClinicalTrials.gov registry

BACKGROUND

Despite specific initiatives and identified needs, most neonatal drugs are still used off-label, with variable dosage administrations and schedules. In high risk preterm and term neonates, drug evaluation is challenging and randomized controlled trials (RCT) are difficult to conduct and even more is the use of a placebo, required in the absence of a reference validated drug to be used as comparator.

METHODS

We analyzed the complete ClinicalTrials.gov registry 1) to describe neonatal RCT involving a placebo, 2) to report on the medical context and ethical aspects of placebo use.

RESULTS

Placebo versus drug RCT (n = 146), either prevention trials (n = 57, 39%) or therapeutic interventions (n = 89, 61%), represent more than a third of neonatal trials registered in the National Institute of Health clinical trial database (USA) since 1999. They mainly concerned preterm infants, evaluating complications of prematurity. Most trials were conducted in the USA, were single centered, and funded by non-profit organizations. For the three top drug trials evaluating steroids (n = 13, 9.6%), erythropoietin (EPO, n = 10, 6.8%) and nitric oxide (NO, n = 9, 6.2%), the objectives of the trial and follow-up were analyzed in more details.

CONCLUSION

Although a matter of debate, the use of placebo should be promoted in neonates to evaluate a potential new treatment, in the absence of reference drug. Analysis of the trials evaluating steroids showed that long-term follow-up of exposed patients, although required by international guidelines, is frequently missing and should be planned to collect additional information and optimize drug evaluation in these high-risk patients.

Children in clinical trials: towards evidence-based pediatric pharmacotherapy using pharmacokinetic-pharmacodynamic modeling

INTRODUCTION

In pediatric pharmacotherapy, many drugs are still used off-label, and their efficacy and safety is not well characterized. Different efficacy and safety profiles in children of varying ages may be anticipated, due to developmental changes occurring across pediatric life.

AREAS COVERED

Beside pharmacokinetic (PK) studies, pharmacodynamic (PD) studies are urgently needed. Validated PKPD models can be used to derive optimal dosing regimens for children of different ages, which can be evaluated in a prospective study before implementation in clinical practice. Strategies should be developed to ensure that formularies update their drug dosing guidelines regularly according to the most recent advances in research, allowing for clinicians to integrate these guidelines in daily practice. Expert commentary: We anticipate a trend towards a systems-level approach in pediatric modeling to optimally use the information gained in pediatric trials. For this approach, properly designed clinical PKPD studies will remain the backbone of pediatric research.

Clinical research in neonates and infants: Challenges and perspectives

To date, up to 65% of drugs used in neonates and infants are off-label or unlicensed, as they were implemented in clinical care without the usual regulatory phases of pharmacological drug development. Pharmacotherapy in this age group is still mainly based on the individual clinical expertise of specialized pediatricians. Pharmacological trials involving neonates are indeed more difficult to perform: appropriate dosing is hampered by the rapid physiological changes occurring at this stage of development, and the selection of proper end-points and biomarkers is complicated by the limited knowledge of the pathophysiology of the specific diseases of infancy. Moreover, there are many ethical challenges in planning and conducting drug studies in pediatric patients (especially in newborns and infants). In the current review, we address some challenges and discuss possible perspectives to stimulate scientific and clinical pharmacological research in neonates and infants. We hereby aim to illustrate the add on value of the regulatory framework for model-based neonatal medicinal development currently used in Europe and the United States. We provide several examples of successful recent pharmacological trials performed in neonates and infants. In these examples, success was ensured by the implementation of specific pharmacokinetic assessments, thanks to accurate drug dosing achieved with a combination of dose validation, population pharmacokinetics and mathematical models of drug clearance and distribution; moreover, age-specific pharmacodynamics was considered via appropriate evaluations of drug efficacy with end-points adapted to the peculiar pathophysiology of diseases in this age group. These "pharmacological" challenges add to the ethical challenges that are always present in planning and conducting clinical studies in neonates and infants and support the opinion that clinical research in pediatrics should be evaluated by ad hoc ethical committees with specific expertise.

Clinical Utility and Safety of a Model-Based Patient-Tailored Dose of Vancomycin in Neonates

Pharmacokinetic modeling has often been applied to evaluate vancomycin pharmacokinetics in neonates. However, clinical application of the model-based personalized vancomycin therapy is still limited. The objective of the present study was to evaluate the clinical utility and safety of a model-based patient-tailored dose of vancomycin in neonates. A model-based vancomycin dosing calculator, developed from a population pharmacokinetic study, has been integrated into the routine clinical care in 3 neonatal intensive care units (Robert Debré, Cochin Port Royal, and Clocheville hospitals) between 2012 and 2014. The target attainment rate, defined as the percentage of patients with a first therapeutic drug monitoring serum vancomycin concentration achieving the target window of 15 to 25 mg/liter, was selected as an endpoint for evaluating the clinical utility. The safety evaluation was focused on nephrotoxicity. The clinical application of the model-based patient-tailored dose of vancomycin has been demonstrated in 190 neonates. The mean (standard deviation) gestational and postnatal ages of the study population were 31.1 (4.9) weeks and 16.7 (21.7) days, respectively. The target attainment rate increased from 41% to 72% without any case of vancomycin-related nephrotoxicity. This proof-of-concept study provides evidence for integrating model-based antimicrobial therapy in neonatal routine care.