Pediatric Obesity: Pharmacokinetic Alterations and Effects on Antimicrobial Dosing

A Quality Initiative to Improve Appropriate Medication Dosing in Pediatric Patients with Obesity

Introduction

Emerging evidence supports the use of alternative dosing weights for medications in patients with obesity. Pediatric obesity presents a particular challenge because most medications are dosed based on patient weight. Additionally, building system-wide pediatric obesity safeguards is difficult due to pediatric obesity definitions of body mass index-percentile-for-age via the Center for Disease Control growth charts. We describe a quality initiative to increase appropriate medication dosing in inpatients with obesity. The specific aim was to increase appropriate dosing for 7 high-risk medications in inpatients with obesity ≥2 years old from 37% to >74% and to sustain for 1 year.

Methods

The Institute for Healthcare Improvement model for improvement was used to plan interventions and track outcomes progress. Interventions included a literature review to establish internal dosing guidance, electronic health record (EHR) functionality to identify pediatric patients with obesity, a default selection for medication weight with an opt-out, and obtaining patient heights in the emergency department.

Results

Appropriate dosing weight use in medication ordered for patients with obesity increased from 37% to 83.4% and was sustained above the goal of 74% for 12 months.

Conclusions

Implementation of EHR-based clinical decision support has increased appropriate evidence-based dosing of medications in pediatric and adult inpatients with obesity. Future studies should investigate the clinical and safety implications of using alternative dosing weights in pediatric patients.

The Impact of Paediatric Obesity on Drug Pharmacokinetics: A Virtual Clinical Trials Case Study with Amlodipine

The incidence of paediatric obesity continues to rise worldwide and contributes to a range of diseases including cardiovascular disease. Obesity in children has been shown to impact upon the plasma concentrations of various compounds, including amlodipine. Nonetheless, information on the influence of obesity on amlodipine pharmacokinetics and the need for dose adjustment has not been studied previously. This study applied the physiologically based pharmacokinetic modelling and established a paediatric obesity population to assess the impact of obesity on amlodipine pharmacokinetics in children and explore the possible dose adjustments required to reach the same plasma concentration as non-obese paediatrics. The difference in predicted maximum concentration (Cmax) and area under the curve (AUC) were significant between children with and without obesity across the age group 2 to 18 years old when a fixed-dose regimen was used. On the contrary, a weight-based dose regimen showed no difference in Cmax between obese and non-obese from 2 to 9 years old. Thus, when a fixed-dose regimen is to be administered, a 1.25- to 1.5-fold increase in dose is required in obese children to achieve the same Cmax concentration as non-obese children, specifically for children aged 5 years and above.

Quantitation of meropenem in dried blood spots using microfluidic-based volumetric sampling coupled with LC-MS/MS bioanalysis in preterm neonates

Meropenem, a carbapenem antibiotic, has been used for empirical and definitive therapy of severe infections for many years. Therapeutic drug monitoring (TDM) plays an indispensable role in the individualization of meropenem particularly in the preterm neonates, a population in which adjusting proper dosages has always been one of the most challenging tasks for their growth changes. In this report, a simple and accurate method for the quantitative analysis of meropenem in dried blood spot (DBS) samples by LC-MS/MS was developed. The traditional DBS drawbacks were conquered in this study by combining microfluidic-based volumetric sampling, shorten drying procedure, and sensitive detection. Moreover, the on-card stability of meropenem was improved obviously. The DBS-based method validation included hematocrit (Hct) effect, selectivity, carry-over, linearity, accuracy, precision, matrix effect, recovery and stability (high temperature and humidity). The calibration linear range of meropenem was 0.3-100 µg/mL. The acceptance criteria of accuracy (relative error < 4.53 %) and precision (coefficient of variation < 8.63 %) were met in all levels of quality control samples. The DBS samples was stable at 40 °C for 12 h, room temperature for 1 day, 4 °C for 7 days, -20 °C for 14 days and -40 °C for 30 days, respectively. A good correlation was observed between DBS concentration and plasma concentration of meropenem. There was 93.4 % of the samples between estimated plasma concentration and plasma concentration within 20 % of the mean of concentration, and no significant Hct effect was observed on the quantification. It has been successfully applied to samples derived from preterm neonates with severe infections. The supported data indicated that the DBS-based method using microfluidic-based volumetric sampling could be an alternative strategy to carry on TDM of meropenem in preterm neonates, with satisfactory performance and logistics advantages.

Clinical Pharmacokinetics of Gentamicin in Various Patient Populations and Consequences for Optimal Dosing for Gram-Negative Infections: An Updated Review

Gentamicin is an aminoglycoside antibiotic with a small therapeutic window that is currently used primarily as part of short-term empirical combination therapy. Gentamicin dosing schemes still need refinement, especially for subpopulations where pharmacokinetics can differ from pharmacokinetics in the general adult population: obese patients, critically ill patients, paediatric patients, neonates, elderly patients and patients on dialysis. This review summarizes the clinical pharmacokinetics of gentamicin in these patient populations and the consequences for optimal dosing of gentamicin for infections caused by Gram-negative bacteria, highlighting new insights from the last 10 years. In this period, several new population pharmacokinetic studies have focused on these subpopulations, providing insights into the typical values of the most relevant pharmacokinetic parameters, the variability of these parameters and possible explanations for this variability, although unexplained variability often remains high. Both dosing schemes and pharmacokinetic/pharmacodynamic (PK/PD) targets varied widely between these studies. A gentamicin starting dose of 7 mg/kg based on total body weight (or on adjusted body weight in obese patients) appears to be the optimal strategy for increasing the probability of target attainment (PTA) after the first administration for the most commonly used PK/PD targets in adults and children older than 1 month, including critically ill patients. However, evidence that increasing the PTA results in higher efficacy is lacking; no studies were identified that show a correlation between estimated or predicted PK/PD target attainment and clinical success. Although it is unclear if performing therapeutic drug monitoring (TDM) for optimization of the PTA is of clinical value, it is recommended in patients with highly variable pharmacokinetics, including patients from all subpopulations that are critically ill (such as elderly, children and neonates) and patients on intermittent haemodialysis. In addition, TDM for optimization of the dosing interval, targeting a trough concentration of at least < 2 mg/L but preferably < 0.5–1 mg/L, has proven to reduce nephrotoxicity and is therefore recommended in all patients receiving more than one dose of gentamicin. The usefulness of the daily area under the plasma concentration–time curve for predicting nephrotoxicity should be further investigated. Additionally, more research is needed on the optimal PK/PD targets for efficacy in the clinical situations in which gentamicin is currently used, that is, as monotherapy for urinary tract infections or as part of short-term combination therapy.

Implementation of a Pharmacist-Driven Vancomycin and Aminoglycoside Dosing Service in a Pediatric Hospital

OBJECTIVE

Pharmacy-driven antibiotic dosing services have been shown to improve clinical outcomes in adult patients. This study evaluated the effect of a pharmacist-driven antimicrobial dosing service on the percentage of therapeutic serum concentrations achieved following initial vancomycin or aminoglycoside dosing regimens. A secondary objective was to determine the effect of the dosing service on nephrotoxicity in pediatric patients.

METHODS

This single-center, retrospective study used data obtained from an electronic medical record to evaluate the utility of a pharmacist-driven vancomycin or aminoglycoside dosing protocol. Assessments of target, subtherapeutic, and supratherapeutic serum concentrations were evaluated. The occurrence of changes in serum creatinine and presentation of acute kidney injury (AKI) were also determined.

RESULTS

The incidence (n [%]) of a therapeutic initial serum concentration was not statistically significant between pre-protocol and post-protocol groups (21 [46.7%] vs 22 [48.9%], respectively; p = 0.834). The incidence of initial supratherapeutic concentrations (19 [42.2%] vs 7 [15.6%]; p = 0.005) and the average number of supratherapeutic concentrations per antibiotic course (0.76 vs 0.26; p = 0.01) were higher in the pre-protocol group compared with the post-protocol group. The incidence of AKI was significantly lower in the post-protocol group (2.2% vs 13.3%; p = 0.049).

CONCLUSIONS

Implementation of a pharmacist-driven dosing service did not affect the likelihood of achieving an initial therapeutic concentration. However, it did reduce the likelihood of both supratherapeutic concentrations and AKI. Additional studies in pediatric patients are needed to affirm the use of pharmacist dosing services.

Ceftazidime dosing in obese patients: is it time for more?

INTRODUCTION

Ceftazidime is used for the treatment of many bacterial infections, including severe P. aeruginosa infections. Like other beta-lactams, inter-individual variability in ceftazidime pharmacokinetics has been described. Due to its related pathophysiological modifications, obesity might influence ceftazidime pharmacokinetics.

AREAS COVERED

The objective of this review is to assess the current state of knowledge about the impact of obesity on ceftazidime treatment. A literature search was conducted on PubMed-MEDLINE (2016-2021) to retrieve pharmacokinetic studies published in English, matching the terms 'ceftazidime' AND 'pharmacokinetics.'

EXPERT OPINION

The impact of obesity on pharmacokinetics is generally poorly known, mainly because obese patients are often excluded from clinical studies. However, the published literature clearly shows that obese patients have significantly lower ceftazidime concentrations. This could be explained by increased volume of distribution and clearance. This low exposure represents a major factor of therapeutic failure, potentially fatal for critically ill patients. While further studies would be useful to better assess the magnitude and understanding of this variability, the use of higher doses of ceftazidime is needed in obese patients. Moreover, therapeutic drug monitoring for dose adaptation is of major interest for these patients, as the efficacy of ceftazidime seems to be directly related to its plasma concentration.

Antifungal Drugs TDM: Trends and Update

PURPOSE

The increasing burden of invasive fungal infections results in growing challenges to antifungal (AF) therapeutic drug monitoring (TDM). This review aims to provide an overview of recent advances in AF TDM.

METHODS

We conducted a PubMed search for articles during 2016-2020 using "TDM" or "pharmacokinetics" or "drug-drug-interaction" with "antifungal," consolidated for each AF. Selection was limited to English language articles with human data on drug exposure.

RESULTS

More than 1000 articles matched the search terms. We selected 566 publications. The latest findings tend to confirm previous observations in real-life clinical settings. The pharmacokinetic variability related to special populations is not specific but must be considered. AF benefit-to-risk ratio, drug-drug interaction (DDI) profiles, and minimal inhibitory concentrations for pathogens must be known to manage at-risk situations and patients. Itraconazole has replaced ketoconazole in healthy volunteers DDI studies. Physiologically based pharmacokinetic modeling is widely used to assess metabolic azole DDI. AF prophylactic use was studied more for Aspergillus spp. and Mucorales in oncohematology and solid organ transplantation than for Candida (already studied). Emergence of central nervous system infection and severe infections in immunocompetent individuals both merit special attention. TDM is more challenging for azoles than amphotericin B and echinocandins. Fewer TDM requirements exist for fluconazole and isavuconazole (ISZ); however, ISZ is frequently used in clinical situations in which TDM is recommended. Voriconazole remains the most challenging of the AF, with toxicity limiting high-dose treatments. Moreover, alternative treatments (posaconazole tablets, ISZ) are now available.

CONCLUSIONS

TDM seems to be crucial for curative and/or long-term maintenance treatment in highly variable patients. TDM poses fewer cost issues than the drugs themselves or subsequent treatment issues. The integration of clinical pharmacology into multidisciplinary management is now increasingly seen as a part of patient care.

Dosing Common Medications in Hospitalized Pediatric Patients with Obesity: A Review

Medication management in children and adolescents with obesity is challenging because both developmental and pathophysiological changes may impact drug disposition and response. Evidence to date indicates an effect of obesity on drug disposition for certain drugs used in this population. This work identified published studies evaluating drug dosing, pharmacokinetics (PK), and effect in pediatric patients with obesity, focusing on 70 common medications used in a pediatric network of 42 US medical centers. A PubMed search revealed 33 studies providing PK and/or effectiveness data for 23% (16 of 70) of medications, 44% of which have just one study and can be considered exploratory. This work appraising 4 decades of literature shows several promising approaches: greater use of PK models applied to prospective clinical studies, dosing recommendations derived from both PK and safety, and multiyear effectiveness data on drugs for chronic conditions (e.g., asthma). Most studies make dose recommendations but are weakened by retrospective study design, small study populations, and no controls or historic controls. Dosing decisions continue to rely on extrapolating knowledge, including targeting systemic drug exposure typically achieved in adults. Optimal weight-based dosing strategies vary by drug and warrant prospective, controlled studies incorporating PK and modeling and simulation to complement clinical assessment.

Vancomycin Dosing in Children With Overweight or Obesity: A Systematic Review and Meta-analysis

CONTEXT

Vancomycin is a medication with potential for significant harm with both overdosing and underdosing. Obesity may affect vancomycin pharmacokinetics and is increasingly common among children.

OBJECTIVE

We aimed to determine if children with overweight or obesity have increased vancomycin trough concentrations with total body weight (TBW) dosing compared with children with normal weight.

DATA SOURCES

We conducted a search of Medline and Medline In-Process & Other Non-Indexed Citations from 1952 (the year vancomycin was discovered) to November 2017.

STUDY SELECTION

Search terms included vancomycin, body weight, and body composition terms and were limited to children. Studies were reviewed and screened by ≥2 reviewers.

DATA EXTRACTION

The primary outcome was vancomycin level. Data were extracted by 2 reviewers. We performed quality assessment using the Newcastle-Ottawa quality assessment scale.

RESULTS

We identified 271 records. After abstract and full-text screening, we identified 7 studies for full review. Six of the 7 studies used a matched case-control design, although there was significant variation in study methodology. Four of the 7 studies were included in a meta-analysis, which revealed a small but significant difference in vancomycin trough levels between children with normal weight and children with overweight or obesity when dosed by using TBW (N = 521; mean difference 2.2 U [95% confidence interval: 1.0-3.4]).

CONCLUSIONS

High-quality data to guide vancomycin dosing in children with obesity are lacking. More studies evaluating dosing strategies in children with obesity are warranted because using TBW to dose vancomycin may lead to higher vancomycin concentrations and potential toxicity.

Impact of obese levels on the hepatic expression of nuclear receptors and drug-metabolizing enzymes in adult and offspring mice

The prevalence of obesity-associated conditions raises new challenges in clinical medication. Although altered expression of drug-metabolizing enzymes (DMEs) has been shown in obesity, the impacts of obese levels (overweight, obesity, and severe obesity) on the expression of DMEs have not been elucidated. Especially, limited information is available on whether parental obese levels affect ontogenic expression of DMEs in children. Here, a high-fat diet (HFD) and three feeding durations were used to mimic different obese levels in C57BL/6 mice. The hepatic expression of five nuclear receptors (NRs) and nine DMEs was examined. In general, a trend of induced expression of NRs and DMEs (except for Cyp2c29 and 3a11) was observed in HFD groups compared to low-fat diet (LFD) groups. Differential effects of HFD on the hepatic expression of DMEs were found in adult mice at different obese levels. Family-based dietary style of an HFD altered the ontogenic expression of DMEs in the offspring older than 15 days. Furthermore, obese levels of parental mice affected the hepatic expression of DMEs in offspring. Overall, the results indicate that obese levels affected expression of the DMEs in adult individuals and that of their children. Drug dosage might need to be optimized based on the obese levels.

Optimizing Antibiotic Drug Therapy in Pediatrics: Current State and Future Needs

The selection of the right antibiotic and right dose necessitates clinicians understand the contribution of pharmacokinetic variability stemming from age-related physiologic maturation and the pharmacodynamics to optimize drug exposure for clinical response. The complexity of selecting the right dose arises from the multiplicity of pediatric age groups, from premature neonates to adolescents. Body size and age (which relate to organ function) must be incorporated to optimize antibiotic dosing in this vulnerable population. In the effort to optimize and individualize drug dosing regimens, clinical pharmacometrics that incorporate population-based pharmacokinetic modeling, Bayesian estimation, and Monte Carlo simulations are utilized as a quantitative approach to understanding and predicting the pharmacology and clinical and microbiologic efficacy of antibiotics. In addition, opportunistic study designs and alternative blood sampling strategies can serve as practical approaches to ensure successful conduct of pediatric studies. This review article examines relevant literature on optimization of antibiotic pharmacotherapy in pediatric populations published within the last decade. Specific pediatric antibiotic data, including beta-lactam antibiotics, aminoglycosides, and vancomycin, are critically evaluated.

Drug Dose Selection in Pediatric Obesity: Available Information for the Most Commonly Prescribed Drugs to Children

Obesity rates continue to rise in children, and little guidance exists regarding the need for adjustment away from total body weight-based doses for those prescribing drugs to this population of children. A majority of drugs prescribed to children with obesity result in either sub-therapeutic or supra-therapeutic concentrations, placing these children at risk for treatment failure and drug toxicities. In this review, we highlight available obesity-specific pharmacokinetic and dosing information for the most frequently prescribed drugs to children in the inpatient and outpatient clinical settings. We also comment on available dosing recommendations for drugs prescribed to treat common pediatric obesity-related comorbidities. This review highlights that there is no safe or proven 'rule of thumb,' for dosing drugs for children with obesity, and a striking lack of pharmacokinetic data to support the creation of dosing guidelines for children with obesity for the most commonly prescribed drugs. It is important that those prescribing for children with obesity are aware of these gaps in knowledge and of potential drug treatment failure or adverse events related to drug toxicity as a result of these knowledge gaps. Until more data are available, we recommend close monitoring of drug response and adverse events in children with obesity receiving commonly prescribed drugs.

Perioperative considerations for airway management and drug dosing in obese children

PURPOSE OF REVIEW

Childhood obesity, a phenomenon that is increasing globally, holds substantial relevance for pediatric anesthesia. In particular, understanding the nuances of airway management and drug dosing in obese children can be daunting.

RECENT FINDINGS

Respiratory adverse events and challenges in managing the airway may be anticipated. In addition, drug-dosing strategies for the obese child are complex and poorly understood although recent advances have clarified the optimal dosing for anesthetics in these children.

SUMMARY

Theoretical knowledge, practical skills, meticulous risk stratification and optimal drug regimens are crucial to ensure the safe conduct of anesthesia for obese children.

Inconsistencies in dosage practice in children with overweight or obesity: A retrospective cohort study

Obesity can affect the pharmacokinetics of most drugs, which may result in under- or overdosing if traditional pediatric dosing strategies are used. To investigate currently applied dosage strategies in children with overweight or obesity (overweight/obesity), in a clinical treatment facility. In particular, whether dosing guidelines were available and metrics of body size applied. A retrospective cohort study of 200 patients admitted to the Danish Children's Obesity Clinic. Data were collected from 2007 to 2015. Overweight/obese children 3-18 years were included if they had at least one drug prescription. Overall there were 658 prescriptions, primarily analgesics, psychotropics, asthma medications, and antibiotics. Except for one prescription, guidelines for dosage of overweight/obese children were not available in the clinic. In one prescription of gentamicin, the dose was adjusted by a metric body size. Otherwise dose was predominately prescribed either by total body weight or as fixed dose by age, in accordance with the recommendations of normal weight children. In drugs with a narrow therapeutic interval, we found large interindividual variations in dosing regimens, that is, for gentamicin, paracetamol, and prednisolone. Reduction of dose to the maximum recommended adult dose was common practice, when the dose calculated by total body weight (ie, mg/kg) exceeded this maximum. This study highlights the shortage of dosing guidelines in overweight/obese children. We found a large interindividual variability in dosage regimens, even in drugs with narrow therapeutic intervals. The clinicians rely on "best practice", as evidence-based dosage regimens are missing for many drugs prescribed during childhood.

Systemic fluoroquinolone prescriptions for hospitalized children in Belgium, results of a multicenter retrospective drug utilization study

BACKGROUND

Fluoroquinolones (FQ) are increasingly prescribed for children, despite being labeled for only a limited number of labeled pediatric indications. In this multicenter retrospective drug utilization study, we analyzed indications for systemic FQ prescriptions in hospitalized children and the appropriateness of the prescribed dose.

METHODS

Using data obtained from electronic medical files, the study included all children who received a systemic FQ prescription in two Belgian university children's hospitals between 2010 and 2013. Two authors reviewed prescribed daily doses. Univariate and multivariate logistic regression models were used to analyze risk factors for inadequately dosing. Results262 FQ prescriptions for individual patients were included for analysis. 16.8% of these prescriptions were for labeled indications, and 35.1% were guided by bacteriological findings. Prescribed daily dose was considered to be inappropriate in 79 prescriptions (30.2%). Other FQ than ciprofloxacin accounted for 9 prescriptions (3.4%), of which 8 were correctly dosed. Underdosing represented 45 (56.9%) dosing errors. Infants and preschool children were at particular risk for dosing errors, with associated adjusted OR of 0.263 (0.097-0.701) and 0.254 (0.106-0.588) respectively.

CONCLUSIONS

FQ were often prescribed off-label and not guided by bacteriological findings in our study population. Dosing errors were common, particularly in infants and preschool children. FQ prescriptions for children should be improved by specific pediatric antimicrobial stewardship teams. Furthermore, pharmacokinetic studies should optimise dosing recommendations for children.

Drug Dosing in Obese Children: Challenges and Evidence-Based Strategies

With the alarming increase of obesity in children, pediatricians are increasingly being confronted with difficult dosing decisions. Many drug labels do not provide specific dosing instructions for children who are obese. In this article, we describe the physiologic parameters altered by obesity and their influences on drug disposition and effect. We review the principles of allometry, and the key pharmacokinetic parameters that can be used to derive age appropriate dosing regimens. Last, we illustrate how appropriate weight descriptors can be selected, and how important PK parameters can be extrapolated for dosing in obese children when pediatric pharmacokinetic information is available.