Pediatric Pharmacology for the Primary Care Provider: Advances and Limitations.

Despite >1 in 5 children taking prescription drugs in the United States, off-label drug use is common. To increase the study of drugs in children, regulatory bodies have enacted legislation to incentivize and require pediatric drug studies. As a result of this legislation, novel trial approaches, and an increase in personnel with pediatric expertise, there have been numerous advancements in pediatric drug development. With this review, we aim to highlight developments in pediatric pharmacology over the past 6 years for the most common disease processes that may be treated pharmacologically by the pediatric primary care provider. Using information extracted from label changes between 2018 and 2023, the published literature, and Clinicaltrials.gov, we discuss advances across multiple therapeutic areas relevant to the pediatric primary care provider, including asthma, obesity and related disorders, mental health disorders, infections, and dermatologic conditions. We highlight instances in which new drugs have been developed on the basis of a deeper mechanistic understanding of illness and instances in which labels have been expanded in older drugs on the basis of newly available data. We then consider additional factors that affect pediatric drug use, including cost and nonpharmacologic therapies. Although there is work to be done, efforts focused on pediatric-specific drug development will increase the availability of evidence-based, labeled guidance for commonly prescribed drugs and improve outcomes through the safe and effective use of drugs in children.

Acyclovir Dosing Practices Across a Multicenter Cohort of Neonatal Intensive Care Units.

BACKGROUND: Acyclovir is the first-line therapy for neonatal herpes simplex virus infections. Therapy can mitigate morbidity and mortality but carries a risk for toxicity. We aimed to compare acyclovir dosing in neonatal intensive care units to published recommendations based on population pharmacokinetic (PopPK) analysis. METHODS: We performed a multicenter cohort study of infants in neonatal intensive care units managed by the Pediatrix Medical Group from 1997 to 2020. We included all infants who received acyclovir with complete dosing information. Our primary outcome was the proportion of courses with dosing within 80%-120% of the PopPK recommended daily dose and at the recommended dosing frequency. We compared dosing before and after the publication of the 2014 PopPK recommendations using linear probability modeling. RESULTS: We identified 6862 infants with complete dosing information across 308 centers. Dosing met PopPK recommendations for 41% of treatment courses for infants <30 weeks postmenstrual age (PMA), 71% for infants 30 to <36 weeks PMA and <1% for infants ≥ 36 weeks PMA. Comparison of dosing from 1997 to 2013 with that from 2015 to 2020 showed a significant increase in dosing meeting PopPK recommendations for infants <30 weeks PMA (P = 0.008) and infants 30 to <36 weeks PMA (P = 0.02) but not infants ≥ 36 weeks PMA (P = 0.29). No significant increase in dosing meeting PopPK recommendations was seen for any PMA group when comparison was limited to more recent years (2008-2013 vs. 2015-2020). CONCLUSIONS: Dosing meeting PopPK recommendations increased over time for some PMA groups, but dosing different than PopPK recommendations remains common. More research is needed to clarify optimal dosing strategies in these infants.

Use of Speckle-Tracking Echocardiography in Septic Cardiomyopathy in Critically Ill Children: A Narrative Review.

OBJECTIVES: In critically ill children with severe sepsis, septic cardiomyopathy (SCM) denotes the subset of patients who have myocardial dysfunction with poor response to fluid and inotropic support, and higher mortality risk. The objective of this review was to evaluate the role of speckle-tracking echocardiography (STE) in the diagnosis and prognosis of pediatric SCM in the PICU setting. DATA SOURCES: We performed detailed searches using PubMed, Scopus, Web of Science, and Google Scholar. Reference lists of all included studies were also examined for further identification of potentially relevant studies. STUDY SELECTION: Studies with the following medical subject headings and keywords were selected: speckle-tracking echocardiography, strain imaging, global longitudinal strain, echocardiography, sepsis, severe sepsis, septic shock, septic cardiomyopathy, and myocardial dysfunction. DATA EXTRACTION: The following data were extracted from all included studies: demographics, diagnoses, echocardiographic parameters, severity of illness, PICU management, and outcomes. DATA SYNTHESIS: STE is a relatively new echocardiographic technique that directly quantifies myocardial contractility. It has high sensitivity in diagnosing SCM, correlates well with illness severity, and has good prognosticating value as compared with conventional echocardiographic parameters. Further studies are required to establish its role in evaluating biventricular systolic and diastolic dysfunction, and to investigate whether it has a role in individualizing treatment and improving treatment outcomes in this group of patients. CONCLUSIONS: STE is a useful adjunct to conventional measures of cardiac function on 2D-echocardiography in the assessment of pediatric SCM in the PICU.

Framework of the strengths and challenges of clinically integrated trials: An expert panel report.

The limitations of the explanatory clinical trial framework include the high expense of implementing explanatory trials, restrictive entry criteria for participants, and redundant logistical processes. These limitations can result in slow evidence generation that is not responsive to population health needs, yielding evidence that is not generalizable. Clinically integrated trials, which integrate clinical research into routine care, represent a potential solution to this challenge and an opportunity to support learning health systems. The operational and design features of clinically integrated trials include a focused scope, simplicity in design and requirements, the leveraging of existing data structures, and patient participation in the entire trial process. These features are designed to minimize barriers to participation and trial execution and reduce additional research burdens for participants and clinicians alike. Broad adoption and scalability of clinically integrated trials are dependent, in part, on continuing regulatory, healthcare system, and payer support. This analysis presents a framework of the strengths and challenges of clinically integrated trials and is based on a multidisciplinary expert "Think Tank" panel discussion that included representatives from patient populations, academia, non-profit funding agencies, the U.S. Food and Drug Administration, and industry.

Application of Physiologically Based Pharmacokinetic Modeling to Characterize the Effects of Age and Obesity on the Disposition of Levetiracetam in the Pediatric Population.

BACKGROUND: Levetiracetam is an antiseizure medication used for several seizure types in adults and children aged 1 month and older; however, due to a lack of data, pharmacokinetic (PK) variability of levetiracetam is not adequately characterized in certain populations, particularly neonates, children younger than 2 years of age, and children older than 2 years of age with obesity. OBJECTIVE: This study aimed to address the gap by leveraging PK data from two prospective standard-of-care pediatric trials (n = 88) covering an age range from 1 month to 19 years, including those with obesity (64%), and applying a physiologically based PK (PBPK) modeling framework. METHODS: A published PBPK model of levetiracetam for children aged 2 years and older was extended to pediatric patients younger than 2 years of age and patients older than 2 years of age with obesity by accounting for the obesity and age-related changes in PK using PK-Sim® software. The prospective pediatric data, along with the literature data for neonates and children younger than 2 years of age, were used to evaluate the extended PBPK models. RESULTS: Overall, 82.4% of data fell within the 90% interval of model-predicted concentrations, with an average fold error within twofold of the accepted criteria. PBPK modeling revealed that children with obesity had lower weight-normalized clearances (0.053 L/h/kg) on average than children without obesity (0.063 L/h/kg). The effect of maturation was well-characterized, resulting in comparable PBPK-simulated, weight-normalized clearances for neonates and children younger than 2 years of age reported from the literature. CONCLUSIONS: PBPK modeling simulations revealed that the current US FDA-labeled pediatric dosing regimen listed in the prescribing information can produce the required exposure of levetiracetam in these target populations with dose adjustments for children with obesity aged 4 years to younger than 16 years.

Correlating Severity of Pulmonary Hypertension by Echocardiogram with Mortality in Premature Infants with Bronchopulmonary Dysplasia.

OBJECTIVE: Bronchopulmonary dysplasia (BPD) is the most common complication of preterm birth. Infants with BPD are at increased risk for pulmonary hypertension (PH). Cardiac catheterization is the gold standard for diagnosing PH, but cardiac catheterization is challenging to perform in small, sick, premature infants. The utility of echocardiography for diagnosing PH and predicting outcomes in extremely premature infants has not been clearly defined. Therefore, we sought to use predefined criteria to diagnose PH by echocardiogram and relate PH severity to mortality in extremely premature infants with BPD. STUDY DESIGN: Echocardiograms from 46 infants born ≤28 weeks' postmenstrual age with a diagnosis of BPD were assessed for PH by three pediatric cardiologists using predefined criteria, and survival times among categories of PH patients were compared. A total of 458 echocardiograms were reviewed, and 15 (33%) patients were found to have at least moderate PH. Patients with at least moderate PH had similar demographic characteristics to those with no/mild PH. RESULTS: Ninety percent of infants without moderate to severe PH survived to hospital discharge, compared with 67% of infants with at least moderate PH (p = 0.048). Patients with severe PH had decreased survival to hospital discharge (38%) compared with moderate (100%) and no/mild PH (90%) groups. Kaplan-Meier survival curves also differed among PH severity groups (Wilcoxon p < 0.001). CONCLUSION: Using predefined criteria for PH, premature infants with BPD can be stratified into PH severity categories. Patients diagnosed with severe PH by echocardiogram have significantly reduced survival. KEY POINTS: · A composite score definition of PH by echocardiogram showed high inter- and intrarater reliability.. · Infants with severe PH by echocardiogram had decreased survival rates.. · Early diagnosis of PH by echocardiogram dictates treatment which may improve outcomes..

Abatacept Pharmacokinetics and Exposure Response in Patients Hospitalized With COVID-19: A Secondary Analysis of the ACTIV-1 IM Randomized Clinical Trial.

Importance: The pharmacokinetics of abatacept and the association between abatacept exposure and outcomes in patients with severe COVID-19 are unknown. Objective: To characterize abatacept pharmacokinetics, relate drug exposure with clinical outcomes, and evaluate the need for dosage adjustments. Design, Setting, and Participants: This study is a secondary analysis of data from the ACTIV-1 (Accelerating COVID-19 Therapeutic Interventions and Vaccines) Immune Modulator (IM) randomized clinical trial conducted between October 16, 2020, and December 31, 2021. The trial included hospitalized adults who received abatacept in addition to standard of care for treatment of COVID-19 pneumonia. Data analysis was performed between September 2022 and February 2024. Exposure: Single intravenous infusion of abatacept (10 mg/kg with a maximum dose of 1000 mg). Main Outcomes and Measures: Mortality at day 28 was the primary outcome of interest, and time to recovery at day 28 was the secondary outcome. Drug exposure was assessed using the projected area under the serum concentration time curve over 28 days (AUC0-28). Logistic regression modeling was used to analyze the association between drug exposure and 28-day mortality, adjusted for age, sex, and disease severity. The association between time to recovery and abatacept exposure was examined using Fine-Gray modeling with death as a competing risk, and was adjusted for age, sex, and disease severity. Results: Of the 509 patients who received abatacept, 395 patients with 848 serum samples were included in the population pharmacokinetic analysis. Their median age was 55 (range, 19-89) years and most (250 [63.3%]) were men. Abatacept clearance increased with body weight and more severe disease activity at baseline. Drug exposure was higher in patients who survived vs those who died, with a median AUC0-28 of 21 428 (range, 8462-43 378) mg × h/L vs 18 262 (range, 9628-27 507) mg × h/L (P < .001). Controlling for age, sex, and disease severity, an increase of 5000 units in AUC0-28 was associated with lower odds of mortality at day 28 (OR, 0.52 [95% CI, 0.35-0.79]; P = .002). For an AUC0-28 of 19 400 mg × h/L or less, there was a higher probability of recovery at day 28 (hazard ratio, 2.63 [95% CI, 1.70-4.08] for every 5000-unit increase; P < .001). Controlling for age, sex, and disease severity, every 5000-unit increase in AUC0-28 was also associated with lower odds of a composite safety event at 28 days (OR, 0.46 [95% CI, 0.33-0.63]; P < .001). Using the dosing regimen studied in the ACTIV-1 IM trial, 121 of the 395 patients (30.6%) would not achieve an abatacept exposure of at least 19 400 mg × h/L, particularly at the extremes of body weight. Using a modified, higher-dose regimen, only 12 patients (3.0%) would not achieve the hypothesized target abatacept exposure. Conclusions and Relevance: In this study, patients who were hospitalized with severe COVID-19 and achieved higher projected abatacept exposure had reduced mortality and a higher probability of recovery with fewer safety events. However, abatacept clearance was high in this population, and the current abatacept dosing (10 mg/kg intravenously with a maximum of 1000 mg) may not achieve optimal exposure in all patients. Trial Registration: ClinicalTrials.gov Identifier: NCT04593940.

A Master Protocol Template for Pediatric ARDS Studies.

BACKGROUND: Pediatric ARDS is associated with significant morbidity and mortality. High-quality data from clinical trials in children are limited due to numerous barriers to their design and execution. Here we describe the collaborative development of a master protocol as a tool to address some of these barriers and support the conduct of pediatric ARDS studies. METHODS: Using PubMed, we performed a literature search of randomized controlled trials (RCTs) in pediatric ARDS to characterize the current state and evaluate potential benefit of harmonized master protocols. We used a multi-stakeholder, collaborative, and team science-oriented process to develop a master protocol template with links to common data elements (CDEs) for pediatric ARDS trials. RESULTS: We identified 11 RCTs that enrolled between 14-200 total subjects per trial. Interventions included mechanical ventilation, prone positioning, corticosteroids, and surfactant. Studies displayed significant heterogeneity in ARDS definition, design, inclusion and exclusion criteria, and reported outcomes. Mortality was reported in 91% of trials and ventilator-free days in 73%. The trial heterogeneity made pooled analysis unfeasible. These findings underscore the need for a method to facilitate combined analysis of future trials through standardization of trial elements. As a potential solution, we developed a master protocol, iteratively revised with input from a multidisciplinary panel of experts and organized into 3 categories: instructions and general information, templated language, and a series of text options of common pediatric ARDS trial scenarios. Finally, we linked master protocol sections to relevant CDEs previously defined for pediatric ARDS and captured in a series of electronic case report forms. CONCLUSIONS: The majority of pediatric ARDS trials identified were small and heterogeneous in study design and outcome reporting. Using a master protocol template for pediatric ARDS trials with CDEs would support combining and comparing pediatric ARDS trial findings and increase the knowledge base.

Sources of pharmacokinetic and pharmacodynamic variability and clinical pharmacology studies of antiseizure medications in the pediatric population.

Multiple treatment options exist for children with epilepsy, including surgery, dietary therapies, neurostimulation, and antiseizure medications (ASMs). ASMs are the first line of therapy, and more than 30 ASMs have U.S. Food and Drug Administration (FDA) approval for the treatment of various epilepsy and seizure types in children. Given the extensive FDA approval of ASMs in children, it is crucial to consider how the physiological and developmental changes throughout childhood may impact drug disposition. Various sources of pharmacokinetic (PK) variability from different extrinsic and intrinsic factors such as patients' size, age, drug-drug interactions, and drug formulation could result in suboptimal dosing of ASMs. Barriers exist to conducting clinical pharmacological studies in neonates, infants, and children due to ethical and practical reasons, limiting available data to fully characterize these drugs' disposition and better elucidate sources of PK variability. Modeling and simulation offer ways to circumvent traditional and intensive clinical pharmacology methods to address gaps in epilepsy and seizure management in children. This review discusses various physiological and developmental changes that influence the PK and pharmacodynamic (PD) variability of ASMs in children, and several key ASMs will be discussed in detail. We will also review novel trial designs in younger pediatric populations, highlight the role of extrapolation of efficacy in epilepsy, and the use of physiologically based PK modeling as a tool to investigate sources of PK/PD variability in children. Finally, we will conclude with current challenges and future directions for optimizing the efficacy and safety of these drugs across the pediatric age spectrum.

Opportunistic dried blood spot sampling validates and optimizes a pediatric population pharmacokinetic model of metronidazole.

Pharmacokinetic models rarely undergo external validation in vulnerable populations such as critically ill infants, thereby limiting the accuracy, efficacy, and safety of model-informed dosing in real-world settings. Here, we describe an opportunistic approach using dried blood spots (DBS) to evaluate a population pharmacokinetic model of metronidazole in critically ill preterm infants of gestational age (GA) ≤31 weeks from the Metronidazole Pharmacokinetics in Premature Infants (PTN_METRO, NCT01222585) study. First, we used linear correlation to compare 42 paired DBS and plasma metronidazole concentrations from 21 preterm infants [mean (SD): post natal age 28.0 (21.7) days, GA 26.3 (2.4) weeks]. Using the resulting predictive equation, we estimated plasma metronidazole concentrations (ePlasma) from 399 DBS collected from 122 preterm and term infants [mean (SD): post natal age 16.7 (15.8) days, GA 31.4 (5.1) weeks] from the Antibiotic Safety in Infants with Complicated Intra-Abdominal Infections (SCAMP, NCT01994993) trial. When evaluating the PTN_METRO model using ePlasma from the SCAMP trial, we found that the model generally predicted ePlasma well in preterm infants with GA ≤31 weeks. When including ePlasma from term and preterm infants with GA >31 weeks, the model was optimized using a sigmoidal Emax maturation function of postmenstrual age on clearance and estimated the exponent of weight on volume of distribution. The optimized model supports existing dosing guidelines and adds new data to support a 6-hour dosing interval for infants with postmenstrual age >40 weeks. Using an opportunistic DBS to externally validate and optimize a metronidazole population pharmacokinetic model was feasible and useful in this vulnerable population.

Indomethacin Pharmacokinetics and Pharmacodynamics in Pregnancies With Preterm Labor: The Need for Dose-Ranging Trials.

The use of indomethacin to delay delivery in preterm labor (PTL) is widely accepted; however, the optimal dosage of indomethacin in pregnancy is unknown. Here, we perform population pharmacokinetic (PK) and pharmacodynamic (PD) analyses, characterize the plasma disposition of indomethacin in pregnant women with PTL, and relate indomethacin exposure to delayed delivery and maternal/neonatal safety. We analyzed plasma and urine samples collected from a multicenter, prospective, opportunistic PK/PD study of indomethacin in pregnant women 12-32 weeks gestation admitted with PTL. Ninety-four participants with 639 plasma concentrations for indomethacin were included in the analysis. The final population PK (popPK) model for indomethacin was a 2-compartment structural model with first-order absorption and elimination and a covariate effect of body mass index on apparent oral clearance. We observed a 21%-60% increase in apparent oral clearance observed during pregnancy. There was no clear association between indomethacin exposure and maternal or neonatal safety outcomes, or with the magnitude of delayed delivery; however, 96.7% of women treated with indomethacin had a delivery that was delayed at least 48 hours. Given the changes to indomethacin apparent oral clearance during pregnancy, and the lack of relationship between indomethacin exposure and safety, dose-finding studies of indomethacin in pregnant women with PTL may help clarify the most safe and efficacious dosage and duration of indomethacin.

Drug development for major chronic health conditions-aligning with growing public health needs: Proceedings from a multistakeholder think tank.

The global pharmaceutical industry portfolio is skewed towards cancer and rare diseases due to more predictable development pathways and financial incentives. In contrast, drug development for major chronic health conditions that are responsible for a large part of mortality and disability worldwide is stalled. To examine the processes of novel drug development for common chronic health conditions, a multistakeholder Think Tank meeting, including thought leaders from academia, clinical practice, non-profit healthcare organizations, the pharmaceutical industry, the Food and Drug Administration (FDA), payors as well as investors, was convened in July 2022. Herein, we summarize the proceedings of this meeting, including an overview of the current state of drug development for chronic health conditions and key barriers that were identified. Six major action items were formulated to accelerate drug development for chronic diseases, with a focus on improving the efficiency of clinical trials and rapid implementation of evidence into clinical practice.

Prescribing practices of inhaled corticosteroids for premature infants in the neonatal intensive care unit.

OBJECTIVE: Despite limited safety and efficacy data, inhaled corticosteroids (ICS) are prescribed to premature infants in the neonatal intensive care unit (NICU). We examined contemporary use and risk factors for ICS use in the NICU. STUDY DESIGN: Infants <33 weeks gestational age and <1500 gm birth weight discharged from Pediatrix Medical Group NICUs between 2010 and 2020 were included. We evaluated the association between ICS prescription and clinical characteristics using univariable and multivariable logistic regression. RESULTS: Of 74,123 infants from 308 NICUs, 9253 (12.5%) were prescribed ICS: budesonide, fluticasone, or beclomethasone. Diagnosis of bronchopulmonary dysplasia (BPD), earlier gestational age, male sex, longer mechanical ventilation, oxygen support, and systemic steroids were independent risk factors for ICS prescription. CONCLUSIONS: Use of ICS is common in many NICUs and is associated with a diagnosis of BPD and healthcare utilization. Prospective trials are needed to establish the safety, efficacy, and optimal indication in this vulnerable population.

Population Pharmacokinetics of Caffeine in Neonates with Congenital Heart Disease and Associations with Acute Kidney Injury.

Cardiac surgery-associated acute kidney injury (CS-AKI) occurs in approximately 65% of neonates undergoing cardiac surgery on cardiopulmonary bypass and contributes to morbidity and mortality. Caffeine may reduce CS-AKI by counteracting adenosine receptor upregulation after bypass, but pharmacokinetics (PK) in this population are unknown. The goal of our analysis is to address knowledge gaps in age-, disease-, and bypass-related effects on caffeine disposition and explore preliminary associations between caffeine exposure and CS-AKI using population PK modeling techniques and an opportunistic, electronic health record-integrated trial design. We prospectively enrolled neonates receiving preoperative caffeine per standard of care and collected PK samples. We retrospectively identified neonates without caffeine exposure undergoing surgery on bypass as a control cohort. We followed US Food and Drug Administration guidance for population PK model development using NONMEM. Effects of clinical covariates on PK parameters were evaluated. We simulated perioperative exposures and used multivariable logistic regression to evaluate the association between caffeine exposure and CS-AKI. Twenty-seven neonates were included in model development. A 1-compartment model with bypass time as a covariate on clearance and volume of distribution best fit the data. Twenty-three neonates with caffeine exposure and 109 controls were included in the exposure-response analysis. Over half of neonates developed CS-AKI. On multivariable analysis, there were no significant differences between CS-AKI with and without caffeine exposure. Neonates with single-ventricle heart disease without CS-AKI had consistently higher simulated caffeine exposures. Our results highlight areas for further study to better understand disease- and bypass-specific effects on drug disposition and identify populations where caffeine may be beneficial.

Underimmunization of very low birth weight infants at discharge from the neonatal intensive care unit.

OBJECTIVE: To quantify immunization status among premature infants discharged from neonatal intensive care units (NICUs), and identify risk factors for underimmunization. STUDY DESIGN: We performed a cohort study of infants <33 weeks gestation discharged home between 2011 and 2020 from 241 NICUs. Using multivariable logistic regression, we examined the association between risk factors and underimmunization at discharge, defined as <1 dose of 5 vaccine types when discharged at 60-119 days of age and <2 doses when discharged at 120-179 days of age. RESULTS: Of 30,766 infants discharged at 60-119 days of age, 14% were underimmunized. Among 4358 infants discharged at 120-179 days of age, 53% were underimmunized. For infants discharged at 60-119 days of age, ventilator support within 30 days of discharge was associated with underimmunization. Having a surgical procedure was associated with underimmunization in both groups. CONCLUSION: A large proportion of premature infants discharged from the NICU are underimmunized.

A reappraisal of risk factors for hypertension after pediatric acute kidney injury.

BACKGROUND: Acute kidney injury (AKI) is common in hospitalized children and increases the risk of chronic kidney disease (CKD) and hypertension, but little is known about the patient level risk factors for pediatric hypertension after AKI. The aims of this study are to evaluate the prevalence and risk factors for new onset hypertension in hospitalized children with AKI and to better understand the role of acute kidney disease (AKD) in the development of hypertension. METHODS: This study was an observational cohort of all children ≤ 18 years old admitted to a single tertiary care children's hospital from 2015 to 2019 with a diagnosis of AKI. Hypertension was defined as blood pressure > 95th percentile for sex, age, height, diagnosis of hypertension on the problem list, or prescription of antihypertensive medication for > 90 days after AKI. RESULTS: A total of 410 children were included in the cohort. Of these, 78 (19%) developed hypertension > 90 days after AKI. A multivariable logistic regression model identified AKD, need for kidney replacement therapy, congenital heart disease, and non-kidney solid organ transplantation as risk factors for hypertension after AKI. CONCLUSIONS: Incident hypertension after 3 months is common among hospitalized children with AKI, and AKD, need for dialysis, congenital heart disease, and non-kidney solid organ transplant are significant risk factors for hypertension after AKI. Monitoring for hypertension development in these high-risk children is critical to mitigate long-term adverse kidney and cardiovascular outcomes.

Pharmacokinetics and Proposed Dosing of Levetiracetam in Children With Obesity.

OBJECTIVE: Characterize levetiracetam pharmacokinetics (PK) in children with obesity to inform dosing. METHODS: Children 2 to <21 years old receiving standard of care oral levetiracetam across two opportunistic studies provided blood samples. Levetiracetam plasma PK data were analyzed with a nonlinear mixed-effects modeling approach. Indirect measures for body size and covariates were tested for model inclusion. Individual empirical Bayesian estimates using the final model parameters were compared by obesity status. Monte Carlo simulation using total body weight was performed in children with normal estimated glomerular filtration rate to identify dosing for children with obesity that resulted in comparable exposures to normal weight adults and children after receiving label dosing. RESULTS: The population PK model was developed from 341 plasma concentrations from 169 children. A 1-compartment model best fit the data with fat-free mass as a significant covariate. Compared with children with normal weight, children with obesity had significantly lower body weight-normalized clearance (median [range], 4.77 [1.49-10.44] and 3.71 [0.86-13.55] L/h/70 kg, respectively). After label dosing with the oral formulation in children with obesity 4 to <16 years old, maximum and minimum steady-state concentrations were higher (25% and 41%, respectively [oral solution] and 27% and 19%, respectively [tablet]) compared with children with normal weight. Comparable exposures between children with and without obesity were achieved with weight-tiered dosing regimens of <75 kg or ≥75 kg. CONCLUSIONS: Weight-tiered dosing for levetiracetam oral solution and tablets for children with obesity 4 to <16 years old results in more comparable exposures to children of normal weight.