Child and Adolescent Bariatric Surgery in an Urban Tertiary Center: Special Anesthetic Considerations for Obesity.

Children and adolescents with obesity who present for weight loss surgery are a unique subset of patients. A thorough understanding of the perioperative needs of these individuals is essential to avoid deleterious complications. This review illustrates the necessity for specialized care, including the continued need of specified drug dosing and a systematic approach in the management of the pediatric bariatric patient.

The European Medicines Agency Experience With Pediatric Dose Selection.

Getting the right dose regimen for children and adolescents is important but poses great scientific, practical, and ethical challenges. At the same time, the availability of data in adults is a huge advantage and needs to be used optimally when designing studies in children and analyzing pediatric data. Furthermore, the processes of maturation and growth are always key when selecting doses for children. All the above make study adaptations and model-informed approaches imperative for dose exposure-response characterization and dose selection in children. This article summarizes the experience gained in the European Medicines Agency on this topic and proposes some general guiding principles for defining objectives, study designs, and methodology tools for pediatric dose selection.

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.

Drug Safety in Labeling for Pediatric Drug Development and Dose Selection in Submissions to the US Food and Drug Administration.

Pediatric safety evaluations are an essential part of a pediatric drug development program. Communication of the results of these safety evaluations is primarily accomplished by labeling of the drug either during the initial pediatric drug development program, or during the postmarketing period after drug approval for pediatric patients. During drug development, the dose-adverse drug event (ADE) relationship is an important part of the evaluation, but a consideration for pediatric ADEs that are unrelated to drug dosage must be maintained. Examples of dose-related and non-dose-related ADEs are presented. The failure to label a product for pediatric use has been safety related for a number of development programs. The US Food and Drug Administration's Pediatric Advisory Committee is a primary source of the pediatric postmarketing safety review and has been associated with a number of labeling changes through its ongoing review process. Pediatric drug safety remains a critical part of the assessment of dose-effect relationship in the pediatric patient population during the drug development and postmarketing surveillance process.

Physiologically Based Pharmacokinetic Modeling and Allometric Scaling in Pediatric Drug Development: Where Do We Draw the Line?

Developing medicines for children is now established in legislation in both the United States and Europe; new drugs require pediatric study or investigation plans as part of their development. Particularly in early age groups, many developmental processes are not reflected by simple scalars such as body weight or body surface area, and even projecting doses based on simple allometric scaling can lead to significant overdoses in certain age groups. Modeling and simulation methodology, including physiologically based modeling, has evolved as part of the drug development toolkit and is being increasingly applied to various aspects of pediatric drug development. Pediatric physiologically based pharmacokinetic (PBPK) models account for the development of organs and the ontogeny of specific enzymes and transporters that determine the age-related pharmacokinetic profiles. However, when should this approach be used, and when will simpler methods such as allometric scaling suffice in answering specific problems? The aim of this review article is to illustrate the application of allometric scaling and PBPK in pediatric drug development and explore the optimal application of the latter approach with reference to case examples. In reality, allometric scaling included as part of population pharmacokinetic and PBPK approaches are all part of a model-informed drug development toolkit helping with decision making during the process of drug discovery and development; to that end, they should be viewed as complementary.

Evaluation of Physiologically Based Pharmacokinetic Models to Predict the Absorption of BCS Class I Drugs in Different Pediatric Age Groups.

Age-related changes in many parameters affecting drug absorption remain poorly characterized. The objective of this study was to apply physiologically based pharmacokinetic (PBPK) models in pediatric patients to investigate the absorption and pharmacokinetics of 4 drugs belonging to the Biopharmaceutics Classification System (BCS) class I administered as oral liquid formulations. Pediatric PBPK models built with PK-Sim/MoBi were used to predict the pharmacokinetics of acetaminophen, emtricitabine, theophylline, and zolpidem in different pediatric populations. The model performance for predicting drug absorption and pharmacokinetics was assessed by comparing the predicted absorption profile with the deconvoluted dose fraction absorbed over time and predicted with observed plasma concentration-time profiles. Sensitivity analyses were performed to analyze the effects of changes in relevant input parameters on the model output. Overall, most pharmacokinetic parameters were predicted within a 2-fold error range. The absorption profiles were generally reasonably predicted, but relatively large differences were observed for acetaminophen. Sensitivity analyses showed that the predicted absorption profile was most sensitive to changes in the gastric emptying time (GET) and the specific intestinal permeability. The drug's solubility played only a minor role. These findings confirm that gastric emptying time, more than intestinal permeability or solubility, is a key factor affecting BCS class I drug absorption in children. As gastric emptying time is prolonged in the fed state, a better understanding of the interplay between food intake and gastric emptying time in children is needed, especially in the very young in whom the (semi)fed condition is the prevailing prandial state, and hence prolonged gastric emptying time seems more plausible than the fasting state.

Extrapolation of Efficacy and Dose Selection in Pediatrics: A Case Example of Atypical Antipsychotics in Adolescents With Schizophrenia and Bipolar I Disorder.

Pediatric labeling information for novel atypical antipsychotics can be significantly delayed as the result of time lag between initial drug approval in adults and the completion of pediatric clinical trials. This delay can lead health care providers to rely on limited evidence-based literature to make critical therapeutic decisions for pediatric patients. Effective and scientifically justified dosing recommendations are needed to improve treatment outcomes in pediatric patients with schizophrenia and bipolar I disorder. Extrapolation-based drug development strategies rely on leveraging prior data to reduce evidentiary requirements for newer data in establishing drug efficacy. On January 13, 2020, the US Food and Drug Administration (FDA) released a general advice letter to sponsors highlighting the acceptance of extrapolating efficacy of atypical antipsychotics to pediatric patients. This review provides insight into the FDA's justification for extrapolating efficacy from adult to pediatric patients and provides a rationale for dose selection in pediatric patients with schizophrenia and bipolar I disorder.

Predictive Performance of Physiology-Based Pharmacokinetic Dose Estimates for Pediatric Trials: Evaluation With 10 Bayer Small-Molecule Compounds in Children.

Development and guidance of dosing schemes in children have been supported by physiology-based pharmacokinetic (PBPK) modeling for many years. PBPK models are built on a generic basis, where compound- and system-specific parameters are separated and can be exchanged, allowing the translation of these models from adults to children by accounting for physiological differences. Owing to these features, PBPK modeling is a valuable approach to support clinical decision making for dosing in children. In this analysis, we evaluate pediatric PBPK models for 10 small-molecule compounds that were applied to support clinical decision processes at Bayer for their predictive power in different age groups. Ratios of PBPK-predicted to observed PK parameters for the evaluated drugs in different pediatric age groups were estimated. Predictive performance was analyzed on the basis of a 2-fold error range and the bioequivalence range (ie, 0.8 ≤ predicted/observed ≤ 1.25). For all 10 compounds, all predicted-to-observed PK ratios were within a 2-fold error range (n = 27), with two-thirds of the ratios within the bioequivalence range (n = 18). The findings demonstrate that the pharmacokinetics of these compounds was successfully and adequately predicted in different pediatric age groups. This illustrates the applicability of PBPK for guiding dosing schemes in the pediatric population.

Progress in Drug Development-Pediatric Dose Selection: Workshop Summary.

The "Pediatric Dose Selection" workshop was held in October 2020 and sponsored by the U.S. Food and Drug Administration and the University of Maryland Center for Excellence in Regulatory Science and Innovation. A summary of the presentations in the context of pediatric drug development is summarized in this article.

Early Exposure of Fosphenytoin, Levetiracetam, and Valproic Acid After High-Dose Intravenous Administration in Young Children With Benzodiazepine-Refractory Status Epilepticus.

Fosphenytoin (FOS) and its active form, phenytoin (PHT), levetiracetam (LEV), and valproic acid (VPA) are commonly used second-line treatments of status epilepticus. However, limited information is available regarding LEV and VPA concentrations following high intravenous doses, particularly in young children. The Established Status Epilepticus Treatment Trial, a blinded, comparative effectiveness study of FOS, LEV, and VPA for benzodiazepine-refractory status epilepticus provided an opportunity to investigate early drug concentrations. Patients aged ≥2 years who continued to seizure despite receiving adequate doses of benzodiazepines were randomly assigned to FOS, LEV, or VPA infused over 10 minutes. A sparse blood-sampling approach was used, with up to 2 samples collected per patient within 2 hours following drug administration. The objective of this work was to report early drug exposure of PHT, LEV, and VPA and plasma protein binding of PHT and VPA. Twenty-seven children with median (interquartile range) age of 4 (2.5-6.5) years were enrolled. The total plasma concentrations ranged from 69 to 151.3 µg/mL for LEV, 11.3 to 26.7 µg/mL for PHT and 126 to 223 µg/mL for VPA. Free fraction ranged from 4% to 19% for PHT and 17% to 51% for VPA. This is the first report in young children of LEV concentrations with convulsive status epilepticus as well as VPA concentrations after a 40 mg/kg dose. Several challenges limited patient enrollment and blood sampling. Additional studies with a larger sample size are required to evaluate the exposure-response relationships in this emergent condition.

Pharmacokinetics of Belimumab in Children With Systemic Lupus Erythematosus.

The phase 2 placebo-controlled, double-blind PLUTO trial characterized the pharmacokinetics of belimumab plus standard systemic lupus erythematosus (SLE) therapy in patients with childhood-onset SLE (cSLE) and demonstrated similar efficacy and safety to that in adult SLE. Patients with active cSLE aged 5-17 years were randomized to intravenous belimumab 10 mg/kg every 4 weeks (n = 53). A linear 2-compartment population pharmacokinetics (popPK) model with first-order elimination was developed, and an exploratory exposure-response analysis assessed the impact of between-patient exposure variability on clinical response (SLE Responder Index 4 [SRI4]) in week 52, and occurrence of serious adverse events during the study. The popPK model estimated clearance of 158 mL/day, steady-state volume of distribution of 3.5 L, terminal half-life of 16.3 days, and distribution half-life of 0.8 days in the overall population. Fat-free mass (FFM) better characterized the pharmacokinetics than total body weight and was more consistent with allometric scaling theory; belimumab pharmacokinetics were largely determined by FFM. Age, sex, disease activity, and concomitant medication had no impact on pediatric belimumab exposure after accounting for body size. Individual and median steady-state pediatric pharmacokinetic profiles were similar to known adult profiles and pediatric exposure estimates for belimumab 10 mg/kg intravenously were consistent with adult exposures. Exposures were similar between SRI4 responders and nonresponders, and patients who did or did not experience a serious adverse event. There was no clinically relevant correlation between exposure and efficacy or safety, confirming belimumab 10 mg/kg intravenous dose every 4 weeks as appropriate for pediatric patients with cSLE.

Dosing Recommendations for Pediatric Patients With Renal Impairment.

A treatment gap exists for pediatric patients with renal impairment. Alterations in renal clearance and metabolism of drugs render standard dosage regimens inappropriate and may lead to drug toxicity, but these studies are not routinely conducted during drug development. The objective of this study was to examine the clinical evidence behind current renal impairment dosage recommendations for pediatric patients in a standard pediatric dosing handbook. The sources of recommendations and comparisons included the pediatric dosing handbook (Lexicomp), the U.S. Food and Drug Administration-approved manufacturer's labels, and published studies in the literature. One hundred twenty-six drugs in Lexicomp had pediatric renal dosing recommendations. Only 14% (18 of 126) of Lexicomp pediatric renal dosing recommendations referenced a pediatric clinical study, and 15% of manufacturer's labels (19 of 126) described specific dosing regimens for renally impaired pediatric patients. Forty-two products had published information on pediatric renal dosing, but 19 (45%) were case studies. When pediatric clinical studies were not referenced in Lexicomp, the renal dosing recommendations followed the adult and pediatric dosing recommendations on the manufacturer's label. Clinical evidence in pediatric patients does not exist for most renal dosing recommendations in a widely used pediatric dosing handbook, and the adult renal dosing recommendations from the manufacturer's label are currently the primary source of pediatric renal dosing information.

Influence of MRP3 Genetics and Hepatic Expression Ontogeny for Morphine Disposition in Neonatal and Pediatric Patients.

We have previously reported the influences of OCT1 ontogeny and genetic variation on morphine clearance in neonatal and pediatric patients. In the latter study, plasma morphine-glucuronide levels correlated with patient genotype for the rs4793665 single-nucleotide polymorphism (SNP) at the locus of MRP3, an efflux transporter of morphine glucuronides between hepatocytes and circulating blood. The link between MRP3 activity and overall morphine clearance has not been thoroughly investigated however, and the developmental profile of hepatic MRP3 protein expression remains thinly defined between neonates and adults. In the current study, previously determined morphine clearance values for neonatal (24-58 weeks postmenstrual age, N = 57) and pediatric (5-16 years, n = 85) patients were reanalyzed for correlation to the SNP genotype of patient rs4793665. Among OCT1 wild-type patients, pediatric morphine clearance showed a significant decreasing trend by MRP3 genotypes in the order of CC > CT > TT (P = .014), whereas for neonates, an identical but nonsignificant trend was observed. Pharmacogenetic differences in MRP3 and OCT1 ontogeny were evaluated by Western blot of hepatic membrane fractions from 50 subjects aged 1 day postnatal to 33 years old. Hepatic MRP3 protein level did not vary by rs4793665 genotype, and followed an atypical developmental pattern of increase up to 1-2 years of age, thereafter decreasing during preadolescence before increasing again to adult levels at maturity (17-33 years). By comparison, OCT1 expression was significantly decreased in OCT1 *1/*3 genotyped patients older than 1 year and followed a trajectory consistent with prior studies. Our results suggest that consideration of MRP3 pharmacogenetics and ontogeny may aid in identifying pediatric patients having different/atypical morphine requirements.

Ontogeny and the Application of Pharmacogenomics to Pediatric Drug Development.

Drug product labels are important vehicles for conveying the scientific information needed for the safe and effective use of a medicinal product. Increasingly, pharmacogenomic (PGx) information is being incorporated into US Food and Drug Administration-approved product labels. In the majority of cases, the PGx information in labeling is derived from studies in adults. Observed genotype-phenotype relationships in adults may not always be reflective of those in certain pediatric age groups because of the influence of ontogeny. The quantitative data necessary for modeling certain genomic markers in pediatrics is still lacking, and further research focused on generating this is needed. In addition, drug safety research focused on understanding the potential contributions of ontogeny, PGx and other underlying mechanisms to differences in adverse drug reactions between pediatrics and adults is warranted.

Characterization of Maternal and Neonatal Pharmacokinetic Behavior of Ceftazidime.

Ceftazidime is a parenteral cephalosporin frequently used in pregnant women for treatment of urinary tract or intrauterine infections. Despite its regular use in pregnant women, ceftazidime disposition in both mother and fetus is not well understood, and a pharmacokinetic (PK) model that allows characterization and simulation of both maternal and preterm neonatal ceftazidime disposition is not available. In this study, 10 pregnant women with suspected or proven intrauterine infections in the late second and early third trimester were treated with 1 g of ceftazidime intravenously every 6 hours. During ceftazidime treatment, one maternal and umbilical cord blood sample was taken at delivery to quantify ceftazidime concentrations in the mother and preterm neonate. Data showed that ceftazidime concentrations in the mother were comparable to those observed in the neonate. Based on these data, a PK model was developed to describe maternal disposition, ceftazidime distribution over the placenta, and elimination in the neonate. The maternal substructure of the model was parameterized according to a previously reported ceftazidime model with minor adjustments to account for pregnancy-related effects on renal elimination of ceftazidime. The expanded population PK model with an additional neonatal compartment was fitted to measured drug concentrations in the neonate. The neonatal elimination rate constant at delivery was close to that estimated for the mother. The presented results show that ceftazidime readily crosses the placenta and indicate that perinatal PK behavior of ceftazidime in preterm neonates can be expected to be similar to those observed in their mothers.

Identifying the "Blip on the Radar Screen": Leveraging Big Data in Defining Drug Safety and Efficacy in Pediatric Practice.

The immense amount of electronic health data (pharmacy and administrative claims, electronic health records, and clinical registries) that is being generated every day in the care of patients has the potential to be leveraged for improving clinical decisions at the point of care, uncovering or validating drug efficacy and drug safety. The potential use of big data for improving safe and effective use of medications is especially important in children because of their low drug exposure relative to adults. Electronic health data is collected primarily for clinical or billing purposes and not for research purposes. The major steps involved in data acquisition, extraction, aggregation, analysis, modeling, and interpretation are discussed. It is important to understand the limitation of big data and utilize appropriate study design and statistical methods. Possible applications are presented along with specific examples of how big data has been used in drug research to find that blip on the radar screen that may give an efficacy or safety signal that can lead to further investigation.

Prediction of Clearance in Neonates and Infants (≤ 3 Months of Age) for Drugs That Are Glucuronidated: A Comparative Study Between Allometric Scaling and Physiologically Based Pharmacokinetic Modeling.

The objective of this study was to evaluate the predictive performances of allometric models and a physiologically based pharmacokinetic model (PBPK) to predict clearance of glucuronidated drugs in neonates (≤ 3 months of age). From the literature, clearance values for 9 drugs (glucuronidated) for neonates and adults were obtained. Three allometric models were used to predict clearances of these glucuronidated drugs. A PBPK model was developed using the physicochemical, biopharmaceutical, and metabolic properties together with known pediatric physiology and enzymatic ontogeny. The model was first developed for adult subjects and then verified using external data and then applied to simulations in neonates. The predictive performances of allometric and PBPK models were evaluated by comparing the predicted values of clearance with the observed clearance values in the neonates. For 9 drugs, there were 13 age groups (preterm and term neonates) for which prediction error in mean clearance values within 0.5- to 1.5-fold was observed in 10 and 11 age groups by 2 allometric models and a PBPK model, respectively. The proposed allometric methods can predict mean clearances of glucuronidated drugs in preterm and term neonates (≤ 3 months of age) with reasonable accuracy (within 0.5- to 1.5-fold or 50% error) and are of practical value during neonatal drug development. The predicted mean clearance values of glucuronidated drugs in neonates ≤ 3 months of age by 2 allometric methods were comparable with the PBPK model.