Population pharmacokinetics of continuous-infusion ceftazidime in febrile neutropenic children undergoing HSCT: implications for target attainment for empirical treatment against Pseudomonas aeruginosa

Pharmacokinetic variability and significance of therapeutic drug monitoring for broad-spectrum antimicrobials in critically ill patients

Critically ill patients are susceptible to serious infections due to their compromised conditions and extensive use of medical devices, often requiring empiric broad-spectrum antimicrobial therapy. Failure of antimicrobial therapy in this vulnerable population has a direct impact on the patient's survival; hence, selecting the optimal dosage is critical. This population, however, exhibits complex and diverse disease-related physiological changes that can markedly alter antimicrobial disposition. Inflammatory cytokines overexpressed in the systemic inflammatory response syndrome increase vascular permeability, leading to higher volume of distribution for hydrophilic antimicrobials. These cytokines also downregulate metabolic enzyme activities, reducing the clearance of their substrates. Hypoalbuminemia can increase the volume of distribution and clearance of highly protein-bound antimicrobials. Acute kidney injury decreases, while augmented renal clearance increases the clearance of antimicrobials primarily excreted by the kidneys. Furthermore, continuous renal replacement therapy and extracorporeal membrane oxygenation used in critical illness substantially affect antimicrobial pharmacokinetics. The complex interplay of multiple factors observed in critically ill patients poses a significant challenge in predicting the pharmacokinetics of antimicrobials. Therapeutic drug monitoring is the most effective tool to address this issue, and is proactively recommended for vancomycin, teicoplanin, aminoglycosides, voriconazole, β-lactams, and linezolid in critically ill patients. To streamline this process, model-informed precision dosing is expected to promote personalized medicine for this population.

Population pharmacokinetics and dose optimization of ceftazidime in critically ill children

Objective

The aim of this study was to develop a population pharmacokinetic model for ceftazidime in critically ill children in the pediatric intensive care unit (PICU) and optimize an appropriate dosing regimen for this population.

Methods

We performed a prospective pharmacokinetic study on critically ill children aged 0.03-15 years. A population pharmacokinetic model was developed using the NLME program. Statistical and graphical methods were used to assess the stability and predictive performance of the model. Monte Carlo simulations were conducted to determine the optimal ceftazidime dosing regimen to achieve 70% fT > minimum inhibitory concentration (MIC).

Results

This study included 88 critically ill children and 100 ceftazidime serum concentrations. The pharmacokinetic characteristics of ceftazidime were best described by a one-compartment linear elimination model. The weight and estimated glomerular filtration rate (eGFR) were determinant covariates for the clearance (CL) of ceftazidime. The recommended ceftazidime dosage regimens achieved a probability of target attainment (PTA) >90% for critically ill children at MIC values of 2, 4, and 8 mg/L. For bacterial infection at an MIC of 16 mg/L, it is difficult to achieve effective pharmacodynamic (PD) targets in vivo with the commonly used dose of ceftazidime.

Conclusion

The population pharmacokinetic model of ceftazidime was established in critically ill children. Based on this model, we recommend evidence-based, individualized dosing regimens for subgroups with different weights and renal functions. The current daily dosage for children adequately meets the treatment requirements for MICs of 2, 4, and 8 mg/L, while for bacterial infection at an MIC of 16 mg/L, an elevated dosage regimen may be required.

Clinical Trial Registration

https://www.medicalresearch.org.cn/login, Identifier MR-42-22-000220.

Spanish Society of Hospital Pharmacy and the Spanish Society of Pediatric Infectious Diseases (SEFH-SEIP) National Consensus Guidelines for therapeutic drug monitoring of antibiotic and antifungal drugs in pediatric and newborn patients

Therapeutic monitoring of antibiotics and antifungals based on pharmacokinetic and pharmacodynamic parameters, is a strategy increasingly used for the optimization of therapy to improve efficacy, reduce the occurrence of toxicities, and prevent the selection of antimicrobial resistance, particularly in vulnerable patients including neonates and the critical or immunocompromised host. In neonates and children, infections account for a high percentage of hospital admissions and anti-infectives are the most used drugs. However, pediatric pharmacokinetic and pharmacodynamic studies and the evidence regarding the efficacy and safety of some newly marketed antibiotics and antifungals -usually used off-label in pediatrics- to determine the optimal drug dosage regimens are limited. It is widely known that this population presents important differences in the pharmacokinetic parameters (especially in drug clearance and volume of distribution) in comparison with adults that may alter antimicrobial exposure and, therefore, compromise treatment success. In addition, pediatric patients are more susceptible to potential adverse drug effects and they need closer monitoring. The aim of this document, developed jointly between the Spanish Society of Hospital Pharmacy (SEFH) and the Spanish Society of Pediatric Infectious Diseases (SEIP), is to describe the available evidence on the indications for therapeutic drug monitoring of antibiotics and antifungals in newborn and pediatric patients and to provide practical recommendations for therapeutic drug monitoring in routine clinical practice to optimize pharmacokinetic and pharmacodynamic parameters, efficacy and safety of antibiotics and antifungals in the pediatric population.

[Translated article] Therapeutic Drug Monitoring of antibiotic and antifungical drugs in paediatric and newborn patients. Consensus Guidelines of the Spanish Society of Hospital Pharmacy (SEFH) and the Spanish Society of Paediatric Infectious Diseases (SEIP)

Therapeutic monitoring of antibiotics and antifungals based on pharmacokinetic and pharmacodynamic (PK/PD) parameters is a strategy increasingly used for the optimization of therapy to improve efficacy, reduce the occurrence of toxicities, and prevent the selection of antimicrobial resistance, particularly in vulnerable patients including neonates and the critical or immunocompromised paediatric host. In neonates and children, infections account for a high percentage of hospital admissions, and anti-infectives are the most used drugs. However, paediatric PK/PD studies and the evidence regarding the efficacy and safety of some newly marketed antibiotics and antifungals-usually used off-label in paediatrics-to determine the optimal drug dosage regimens are limited. It is widely known that this population presents important differences in the PK parameters (especially in drug clearance and volume of distribution) in comparison with adults that may alter antimicrobial exposure and, therefore, compromise treatment success. In addition, paediatric patients are more susceptible to potential adverse drug effects and they need closer monitoring. The aim of this document, developed jointly by the Spanish Society of Hospital Pharmacy and the Spanish Society of Paediatric Infectious Diseases, is to describe the available evidence on the indications for therapeutic drug monitoring (TDM) of antibiotics and antifungals in newborn and paediatric patients, and to provide practical recommendations for TDM in routine clinical practice to optimise their dosing, efficacy and safety. Of antibiotics and antifungals in the paediatric population.

Loading Dose of Ceftazidime Needs to Be Increased in Critically Ill Patients: A Retrospective Study to Evaluate Recommended Loading Dose with Pharmacokinetic Modelling

To rapidly achieve ceftazidime target concentrations, a 2 g loading dose (LD) is recommended before continuous infusion, but its adequacy in critically ill patients, given their unique pharmacokinetics, needs investigation. This study included patients from six ICUs in Saint-Etienne and Paris, France, who received continuous ceftazidime infusion with plasma concentration measurements. Using MONOLIX and R, a pharmacokinetic (PK) model was developed, and the literature on ICU patient PK models was reviewed. Simulations calculated the LD needed to reach a 60 mg/L target concentration and assessed ceftazidime exposure for various regimens. Among 86 patients with 223 samples, ceftazidime PK was best described by a one-compartment model with glomerular filtration rate explaining clearance variability. Typical clearance and volume of distribution were 4.45 L/h and 88 L, respectively. The literature median volume of distribution was 37.2 L. Simulations indicated that an LD higher than 2 g was needed to achieve 60 mg/L in 80% of patients, with a median LD of 4.9 g. Our model showed a 4 g LD followed by 6 g/day infusion reached effective concentrations within 1 h, while a 2 g LD caused an 18 h delay in achieving target steady state.

Dose optimization of β-lactam antibiotics in children: from population pharmacokinetics to individualized therapy

INTRODUCTION

β-Lactams are the most widely used antibiotics in children. Their optimal dosing is essential to maximize their efficacy, while minimizing the risk for toxicity and the further emergence of antimicrobial resistance. However, most β-lactams were developed and licensed long before regulatory changes mandated pharmacokinetic studies in children. As a result, pediatric dosing practices are poorly harmonized and off-label use remains common today.

AREAS COVERED

β-Lactam pharmacokinetics and dose optimization strategies in pediatrics, including fixed dose regimens, therapeutic drug monitoring, and model-informed precision dosing are reviewed.

EXPERT OPINION/COMMENTARY

Standard pediatric doses can result in subtherapeutic exposure and non-target attainment for specific patient subpopulations (neonates, critically ill children, e.g.). Such patients could benefit greatly from more individualized approaches to dose optimization, beyond a relatively simple dose adaptation based on weight, age, or renal function. In this context, Therapeutic Drug Monitoring (TDM) and Model-Informed Precision Dosing (MIPD) emerge as particularly promising avenues. Obstacles to their implementation include the lack of strong evidence of clinical benefit due to the paucity of randomized clinical trials, of standardized assays for monitoring concentrations, or of adequate markers for renal function. The development of precision medicine tools is urgently needed to individualize therapy in vulnerable pediatric subpopulations.

Ceftazidime-related neurotoxicity in a patient with renal impairment: a case report and literature review

PURPOSE

We present the case of a 67-year-old woman with severely reduced renal clearance suffering from ceftazidime-induced encephalopathy. Subsequently, we search the literature to review and describe the neurotoxicity of ceftazidime.

METHODS

A search string was developed to search PubMed for relevant cases from which relevant information was extracted. Using the collected data a ROC analysis was performed in R to determine a neurotoxicity threshold.

RESULTS

Our patient suffered from progressive loss of consciousness and myoclonic seizures, with improvements noted a few days after discontinuation of treatment. The dose was not appropriately reduced to take into account her reduced renal function. The highest ceftazidime concentration recorded was 234.9 mg/mL. Using the Naranjo score we found a probable relationship between our patient's encephalopathy and ceftazidime administration. In the literature we found a total of 32 similar cases, most of which also had some form of renal impairment. Using our collected data and ceftazidime concentrations provided in the literature, a ROC analysis provided a neurotoxicity threshold of 78 mg/L for ceftazidime neurotoxicity.

CONCLUSION

Ceftazidime-related neurotoxicity is a known issue, especially in patients with severe renal impairment. Yet no concrete toxicity threshold has been reported so far. We propose the first toxicity threshold for ceftazidime of 78 mg/L. Future prospective studies are needed to validate and optimize the neurotoxicity threshold as upper limit for ceftazidime therapeutic drug monitoring.

Ceftazidime Plasma Concentrations and Neurotoxicity: The Importance of Therapeutic Drug Monitoring in Patients Undergoing Different Modalities of Renal Replacement Therapy. A Grand Round

ABSTRACT

Ceftazidime-avibactam (CTZ-AVM) is a novel cephalosporin/beta-lactamase inhibitor with broad-spectrum activity against multidrug-resistant Pseudomonas aeruginosa . Ceftazidime-induced neurotoxicity is a well-described adverse effect, particularly in patients with renal insufficiency. However, appropriate dosing of ceftazidime-avibactam in patients undergoing renal replacement therapy (RRT) is sparsely investigated, and therapeutic drug monitoring to guide dosing remains lacking. Furthermore, when dose adjustment for impaired renal function is based on CTZ-AVM product information, inferior cure rates have been obtained compared with those with the standard therapy for intra-abdominal infections. Maintaining an effective dose while avoiding toxicity in these patients is challenging. Here, the authors describe the case of a critically ill patient, undergoing 2 modalities of RRT, who developed ceftazidime-induced neurotoxicity as confirmed using ceftazidime therapeutic drug monitoring. This case illustrates a therapeutic drug monitoring-based approach for guiding ceftazidime-avibactam dosing in this context and in diagnosing the cause of neurological symptoms and signs.

Superiority of ceftazidime off-label high-dose regimen in PK/PD target attainment during treatment of extensively drug-resistant Pseudomonas aeruginosa infections in cancer patients

AIM

The objective of this study was to evaluate off-label high-dose ceftazidime population pharmacokinetics in cancer patients with suspected or proven extensively drug-resistant (XDR) Pseudomonas aeruginosa infections and then to compare the achievement of the pharmacokinetic/pharmacodynamic (PK/PD) target after standard and off-label high-dose regimens using population model-based simulations. A further aim was to clinically observe the occurrence of adverse effects during the off-label high-dose ceftazidime treatment.

METHODS

In patients treated with off-label high-dose ceftazidime (3 g every 6 h), blood samples were collected and ceftazidime serum levels measured using LC-MS/MS. A pharmacokinetic population model was developed using a nonlinear mixed-effects modelling approach and Monte Carlo simulations were then used to compare standard and high-dose regimens for PK/PD target attainment.

RESULTS

A total of 14 cancer patients with serious infection suspected of XDR P. aeruginosa aetiology were eligible for PK analysis. XDR P. aeruginosa was confirmed in 10 patients as the causative pathogen. Population ceftazidime volume of distribution was 13.23 L, while clearance started at the baseline of 1.48 L/h and increased by 0.0076 L/h with each 1 mL/min/1.73 m² of eGFR. High-dose regimen showed significantly higher probability of target attainment (i.e., 86% vs. 56% at MIC of 32 mg/L). This was translated into a very low mortality rate of 20%. Only one case of reversible neurological impairment was observed.

CONCLUSION

We proved the superiority of the ceftazidime off-label high-dose regimen in PK/PD target attainment with very low occurrence of adverse effects. The off-label high-dose regimen should be used to optimize treatment of XDR P. aeruginosa infections.

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.

Therapeutic Drug Monitoring of Antibiotics in Critically Ill Children: An Observational Study in a Pediatric Intensive Care Unit

BACKGROUND

Septic critically ill children are at a high risk of inadequate antibiotic exposure, requiring them to undergo therapeutic drug monitoring (TDM). The aim of this study was to describe the use of TDM for antibiotics in critically ill children.

METHODS

The authors conducted a single-center observational study between June and December 2019, with all children treated with antibiotics in a pediatric intensive care unit located in a French university hospital. Standard clinical and laboratory data were recorded. Blood samples were collected for routine laboratory tests, and plasma antibiotic levels were assayed using validated analytical methods.

RESULTS

A total of 209 children received antibiotics. TDM was performed in 58 patients (27.8%) who had a greater mean organ dysfunction (according to the International Pediatric Sepsis Consensus Conference) (3 versus 1 in the non-TDM group; P < 0.05) and were treated with antibiotics for longer. A total of 208 samples were analyzed. The median [interquartile range] assay turnaround time was 3 (1-5) days, and 48 (46.2%) of the 104 initial antibiotic concentration values were below the pharmacokinetic/pharmacodynamic targets. A total of 34 (46%) of the 74 off-target TDM measurements available before the end of the antibiotic treatment prompted dose adjustment. This dose adjustment increased the proportion of on-target TDM measurements (70% versus 20% without adjustment). Subsequent measurements of the minimum inhibitory concentration showed that the use of the European Committee on Antimicrobial Susceptibility Testing's epidemiological cutoff values led to underestimation of pharmacokinetic/pharmacodynamic target attainment in 10 cases (20%).

CONCLUSIONS

TDM seems to be an effective means of optimizing antibiotic exposure in critically ill children. This requires timely plasma antibiotic assays and minimum inhibitory concentration measurements. It is important to define which patients should undergo TDM and how this monitoring should be managed.

A Review of Extended and Continuous Infusion Beta-Lactams in Pediatric Patients

Intravenous beta-lactam antibiotics are the most prescribed antibiotic class in US hospitalized patients of all ages; therefore, optimizing their dosing is crucial. Bactericidal killing is best predicted by the time in which beta-lactam drug concentrations are maintained above the organism's minimum inhibitory concentration (MIC), rather than achievement of a high peak concentration. As such, administration of beta-lactam antibiotics via extended or continuous infusions over a minimum of 3 hours, rather than standard infusions over approximately 30 minutes, has been associated with improved achievement of pharmacodynamic targets and improved clinical outcomes in adult medical literature. This review summarizes the pediatric medical literature. Applicable studies include pharmacodynamic models, case series, retrospective analyses, and prospective studies on the use of extended infusion and continuous infusion penicillins, cephalosporins, carbapenems, and monobactams in neonates, infants, children, and adolescents. Specialized patient populations with unique pharmacokinetics and high-risk infections (neonates, critically ill, febrile neutropenia, cystic fibrosis) are also reviewed. While more studies are needed to confirm prospective clinical outcomes, the current body of evidence suggests extended and continuous infusions of beta-lactam antibiotics are well tolerated in children and improve achievement of pharmacokineticpharmacodynamic targets with similar or superior clinical outcomes, particularly in infections associated with high MICs.

Assessment of a PK/PD Target of Continuous Infusion Beta-Lactams Useful for Preventing Microbiological Failure and/or Resistance Development in Critically Ill Patients Affected by Documented Gram-Negative Infections

BACKGROUND

Emerging data suggest that more aggressive beta-lactam PK/PD targets could minimize the occurrence of microbiological failure and/or resistance development. This study aims to assess whether a PK/PD target threshold of continuous infusion (CI) beta-lactams may be useful in preventing microbiological failure and/or resistance development in critically ill patients affected by documented Gram-negative infections.

METHODS

Patients admitted to intensive care units from December 2020 to July 2021 receiving continuous infusion beta-lactams for documented Gram-negative infections and having at least one therapeutic drug monitoring in the first 72 h of treatment were included. A receiver operating characteristic (ROC) curve analysis was performed using the ratio between steady-state concentration and minimum inhibitory concentration (C_ss/MIC) ratio as the test variable and occurrence of microbiological failure as the state variable. Area under the curve (AUC) and 95% confidence interval (CI) were calculated. Independent risk factors for the occurrence of microbiological failure were investigated using logistic regression.

RESULTS

Overall, 116 patients were included. Microbiological failure occurred in 26 cases (22.4%). A C_ss/MIC ratio ≤ 5 was identified as PK/PD target cut-off with sensitivity of 80.8% (CI 60.6-93.4%) and specificity of 90.5% (CI 74.2-94.4%), and with an AUC of 0.868 (95%CI 0.793-0.924; p < 0.001). At multivariate regression, independent predictors of microbiological failure were C_ss/MIC ratio ≤ 5 (odds ratio [OR] 34.54; 95%CI 7.45-160.11; p < 0.001) and Pseudomonas aeruginosa infection (OR 4.79; 95%CI 1.11-20.79; p = 0.036).

CONCLUSIONS

Early targeting of CI beta-lactams at C_ss/MIC ratio > 5 during the treatment of documented Gram-negative infections may be helpful in preventing microbiological failure and/or resistance development in critically ill patients.

Population pharmacokinetics of vancomycin in paediatric patients with febrile neutropenia and augmented renal clearance: development of new dosing recommendations

OBJECTIVES

The purpose of this study was to evaluate the influence of augmented renal clearance (ARC) on vancomycin clearance and provide dosage recommendations for paediatric patients with febrile neutropenia following HSCT.

METHODS

A population pharmacokinetic analysis was performed based on a two-compartment model structure using a non-linear mixed-effect modelling approach. Monte Carlo simulations were conducted as a target attainment analysis of AUC between 400 mg·h/L and 650 mg·h/L for MRSA at an MIC of 1 mg/L.

RESULTS

A total of 165 paediatric patients and 276 vancomycin serum concentrations were analysed in this study. Age, body weight, estimated glomerular filtration rate (eGFR) and fever (≥38.0°C) were identified as factors that significantly influenced vancomycin clearance. The median eGFR of the population was 143 mL/min/1.73 m2 and 34% of patients showed an eGFR ≥160 mL/min/1.73 m2, which may be classified as ARC. Our simulations showed that current dosing recommendations result in poor target attainment. In particular, children aged 6 months old to 6 years old with ARC require an initial vancomycin dose up to 35%-65% higher than the current dosing guidelines.

CONCLUSIONS

ARC is frequently observed in paediatric patients with post-HSCT febrile neutropenia, resulting in a significant increase in vancomycin clearance. We propose a vancomycin dosing strategy for children with febrile neutropenia following HSCT based on eGFR, age, weight and body temperature.

Population pharmacokinetics of ceftazidime in critically ill children: impact of cystic fibrosis

BACKGROUND

Pharmacokinetics data on ceftazidime are sparse for the paediatric population, particularly for children with cystic fibrosis (CF) or severe infections.

OBJECTIVES

To characterize the population pharmacokinetics of ceftazidime in critically ill children, identify covariates that affect drug disposition and evaluate the current dosing regimens.

METHODS

The study was registered with Clinicaltrials.gov (NCT01344512). Children receiving ceftazidime were selected in 13 French hospitals. Plasma concentrations were determined by UPLC-MS/MS. Population pharmacokinetic analyses were performed using NONMEN software.

RESULTS

One hundred and eight patients, aged 28 days to 12 years, with CF (n = 32), haematology and/or oncology disorders (n = 47) or severe infection (n = 29) were included. Ceftazidime was administered by continuous or intermittent infusions; 271 samples were available for analysis. A two-compartment model with first-order elimination and allometric scaling was developed and covariate analysis showed that ceftazidime pharmacokinetics were also significantly affected by CLCR and CF. Ceftazidime clearance was 82% higher in CF than in non-CF patients. Monte Carlo simulations showed that the percentage of target attainment (PTA) for the target of T>MIC = 65% was (i) lower in CF than in non-CF children with intermittent infusions and (ii) higher with continuous than intermittent infusion in all children.

CONCLUSIONS

The population pharmacokinetics model for ceftazidime in children was influenced by body weight, CLCR and CF. A higher PTA was obtained with continuous versus intermittent infusions. Further studies should explore the benefits of continuous versus intermittent infusion of ceftazidime, including current versus increased doses in CF children.

Optimizing Antibiotic Treatment Strategies for Neonates and Children: Does Implementing Extended or Prolonged Infusion Provide any Advantage?

Optimizing the use of antibiotics has become mandatory, particularly for the pediatric population where limited options are currently available. Selecting the dosing strategy may improve overall outcomes and limit the further development of antimicrobial resistance. Time-dependent antibiotics optimize their free concentration above the minimal inhibitory concentration (MIC) when administered by continuous infusion, however evidences from literature are still insufficient to recommend its widespread adoption. The aim of this review is to assess the state-of-the-art of intermittent versus prolonged intravenous administration of antibiotics in children and neonates with bacterial infections. We identified and reviewed relevant literature by searching PubMed, from 1 January 1 2000 to 15 April 2020. We included studies comparing intermittent versus prolonged/continuous antibiotic infusion, among the pediatric population. Nine relevant articles were selected, including RCTs, prospective and retrospective studies focusing on different infusion strategies of vancomycin, piperacillin/tazobactam, ceftazidime, cefepime and meropenem in the pediatric population. Prolonged and continuous infusions of antibiotics showed a greater probability of target attainment as compared to intermittent infusion regimens, with generally good clinical outcomes and safety profiles, however its impact in terms on efficacy, feasibility and toxicity is still open, with few studies led on children and adult data not being fully extendable.