AUCs and 123s: a critical appraisal of vancomycin therapeutic drug monitoring in paediatrics

Vancomycin in Pediatric Patients with Cystic Fibrosis: Dose Optimization Using Population Pharmacokinetic Approach

BACKGROUND

An increase in Staphylococcus aureus infections has been reported in pediatric patients with cystic fibrosis (CF) over the last few years. This pathogen is commonly treated with vancomycin, an antibiotic for which therapeutic drug monitoring (TDM) is recommended. Updated guidelines were recently published regarding new targets of exposure for the TDM of vancomycin through a Bayesian approach, using population pharmacokinetic (popPK) models.

OBJECTIVES

This study aims to assess the predictive performance of vancomycin popPK models in pediatric patients with CF and to recommend optimal initial dosing regimens based on simulations.

METHODS

Patient data were collected from two centers in Canada, and a literature review was conducted to identify all published vancomycin popPK models for pediatric CF patients. External evaluation and simulations were performed according to patient and occasion of treatment.

RESULTS

A total of 53 vancomycin concentrations were collected from six pediatric CF patients. Only two popPK models of vancomycin for pediatric CF patients were identified through the literature review. The external evaluation results for both centers combined revealed a population bias of 28.1% and an imprecision of 33.7%. A re-estimation of parameters was performed to improve predictive performance. The optimal initial dosing regimen was 15 mg/kg/dose administered every 6 hours according to the per occasion remodel.

CONCLUSION

The predictive performance and identified optimal initial dosing regimens associated with the model were different depending on the data used, showing external evaluation's importance before implementing a model in clinical practice.

Effects of storage up to 1 year on the in vitro antimicrobial activity of preformulated antibiotic-impregnated calcium sulfate beads

OBJECTIVE

To compare antimicrobial activity as demonstrated by the zone of inhibition (ZOI) produced by antibiotic-impregnated calcium sulfate (CaSO4) beads after storage for 0, 3, 6, 9, and 12 months.

STUDY DESIGN

Controlled laboratory study.

SAMPLE POPULATION

Three-millimeter diameter CaSO4 beads impregnated with vancomycin (125 mg/mL), or amikacin (250 mg/mL), or without antibiotic (control).

METHODS

Calcium sulfate beads were created at the onset of the study. Individual beads were separated in sterile containers and stored in a closed cabinet at room temperature and humidity for 0, 3, 6, 9, or 12 months until testing. The ZOI against methicillin-resistant Staphylococcus pseudintermedius, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa was recorded with serial replating on a fresh lawn of bacteria every 24 h until beads failed to produce a ZOI. The ZOIs and their changes were compared with mixed-effects linear models. Eluted concentrations of vancomycin measured with high-performance liquid chromatography were reported.

RESULTS

At 24 h, ZOIs were comparable regardless of time since formulation, except vancomycin against P. aeruginosa, which failed to generate a ZOI. The daily changes of ZOI and duration of activity of antibiotics did not vary between storage length (p > .05). There was no consistent change in eluted drug concentration between storage length of beads.

CONCLUSION

Light protected storage at room temperature for up to 12 months did not impair the in vitro activity of antibiotic-impregnated CaSO4 beads, as demonstrated through ZOIs.

CLINICAL SIGNIFICANCE

When stored correctly, antibiotic-impregnated CaSO4 beads can be used at least up to 12 months after formulation.

Correlation of Calculated Vancomycin Trough Concentrations and Exposure: A Monte Carlo Simulation

BACKGROUND

Current recommendations are to dose vancomycin to target 24-hour area under the curve (AUC) of 400-600 mg·h/L to optimize efficacy and safety. Limited data support AUC monitoring, and some centers continue to use trough concentrations. A target of 10-20 mg/L has been proposed to reduce nephrotoxicity risk.

OBJECTIVE

To use previously published pharmacokinetic equations in a Monte Carlo simulation relating AUC exposure to trough concentrations when targeting an AUC between 400 and 600 mg·h/L.

METHODS

Previously published pharmacokinetic data were used as input parameters for a Monte Carlo simulation using previously published formulae to correlate AUC to simulated trough concentrations. Pharmacokinetic parameters were assumed to occur in a normal distribution pattern. We excluded irrelevant simulated cases. Maintenance doses of 15 mg/kg were rounded to the nearest 250 mg. Calculated trough concentrations for AUCs of both 400 and 600 mg·h/L were evaluated in each simulation.

RESULTS

A total of 10 000 Monte Carlo simulations were performed. Targeting an AUC of 400 mg·h/L resulted in a mean trough concentration of 10.3 ± 0.8 mg/L. Targeting an AUC of 600 mg·h/L resulted in a mean trough concentration of 15.4 ± 1.2 mg/L.

CONCLUSION AND RELEVANCE

We demonstrate that a lower trough concentration range may be supported by an AUC of 400-600 mg·h/L, which may reduce risk and rates of nephrotoxicity without compromising previously established efficacious target trough concentrations.

Optimal Use and Need for Therapeutic Drug Monitoring of Teicoplanin in Children: A Systematic Review

BACKGROUND

Teicoplanin is a glycopeptide antimicrobial that treats serious invasive infections caused by gram-positive bacteria, such as the methicillin-resistant Staphylococcus aureus. Despite some comparable advantages, there is no guideline or clinical recommendation for teicoplanin in the pediatric population, unlike vancomycin where abundant studies and the recently revised guideline on therapeutic drug level monitoring (TDM) exist.

METHODS

The systematic review was performed in accordance with the preferred reporting items for systematic reviews. Two authors (JSC and SHY) searched PubMed, Embase, and Cochrane Library databases using relevant terms independently.

RESULTS

Fourteen studies were finally included with a total of 1,380 patients. TDM was available in 2,739 samples collected in the nine studies. Dosing regimens varied widely, and eight studies used recommended dosing regimens. Timing for measuring TDM was mostly 72-96 hours or longer after the initiation of the first dose, which was expected to be a steady-state. The majority of studies had target trough levels of 10 µg/mL or above. Three studies reported that the clinical efficacy and treatment success rate of teicoplanin was 71.4%, 87.5%, and 88%. Adverse events associated with teicoplanin use were described in six studies with a focus on renal and/or hepatic impairment. Except for one study, no significant relation was noted between the incidence of adverse events and trough concentration.

CONCLUSION

Current evidence on teicoplanin trough levels in pediatric populations is insufficient due to heterogeneity. However, target trough levels with favorable clinical efficacy are achievable by recommended dosing regimen in the majority of patients.

In Outpatients Receiving Parenteral Vancomycin, Dosing Adjustments Produced by Area Under the Curve-Based and Trough-Based Monitoring Differ Only at the Extremes of the Therapeutic Trough Range

Area under the curve (AUC)-based vancomycin dosing reduces nephrotoxicity but is burdensome. Reviewing 115 adults receiving ≥2 weeks of outpatient vancomycin, we found AUC-based and trough-based dose adjustments discordant only for troughs <12 or >16 mg/L. Selective versus universal outpatient AUC calculation would likely offer similar benefit with reduced workload.

Optimization of Vancomycin Initial Dose in Term and Preterm Neonates by Machine Learning

INTRODUCTION

Vancomycin is one of the antibiotics most used in neonates. Continuous infusion has many advantages over intermittent infusions, but no consensus has been achieved regarding the optimal initial dose. The objectives of this study were: to develop a Machine learning (ML) algorithm based on pharmacokinetic profiles obtained by Monte Carlo simulations using a population pharmacokinetic model (POPPK) from the literature, in order to derive the best vancomycin initial dose in preterm and term neonates, and to compare ML performances with those of an literature equation (LE) derived from a POPPK previously published.

MATERIALS AND METHODS

The parameters of a previously published POPPK model of vancomycin in children and neonates were used in the mrgsolve R package to simulate 1900 PK profiles. ML algorithms were developed from these simulations using Xgboost, GLMNET and MARS in parallel, benchmarked and used to calculate the ML first dose. Performances were evaluated in a second simulation set and in an external set of 82 real patients and compared to those of a LE.

RESULTS

The Xgboost algorithm yielded numerically best performances and target attainment rates: 46.9% in the second simulation set of 400-600 AUC/MIC ratio vs. 41.4% for the LE model (p = 0.0018); and 35.3% vs. 28% in real patients (p = 0.401), respectively). The Xgboost model resulted in less AUC/MIC > 600, thus decreasing the risk of nephrotoxicity.

CONCLUSION

The Xgboost algorithm developed to estimate the initial dose of vancomycin in term or preterm infants has better performances than a previous validated LE and should be evaluated prospectively.

Association of Vancomycin Trough Concentration and Clearance With Febrile Neutropenia in Pediatric Patients

BACKGROUND

Febrile neutropenia promotes renal drug excretion. Adult and pediatric patients with febrile neutropenia exhibit a lower vancomycin concentration/dose (relative to bodyweight) ratio than those with other infections. In pediatric patients, renal function relative to bodyweight varies depending on age, and vancomycin clearance is age dependent. This study aimed to analyze the effects of febrile neutropenia on the pharmacokinetics of vancomycin in age-stratified pediatric patients.

METHODS

This retrospective, single-center, observational cohort study analyzed 112 hospitalized pediatric patients who met the selection criteria and intravenously received vancomycin at the Department of Pediatrics of the Oita University Hospital between April 2011 and October 2019.

RESULTS

The febrile neutropenia (n = 46) cohort exhibited a significantly higher estimated glomerular filtration rate than the nonfebrile neutropenia (n = 66) cohort. Compared with those in the nonfebrile neutropenia cohort, the daily vancomycin dose relative to bodyweight and vancomycin clearance were significantly higher, and the vancomycin trough concentration and vancomycin concentration/dose ratio were significantly lower in the febrile neutropenia cohort. In the age groups of 1-6 and 7-12 years, compared with those in the nonfebrile neutropenia cohort, the vancomycin concentration/dose ratio was significantly lower, and vancomycin clearance was significantly higher in the febrile neutropenia cohort. Univariate and multivariate analyses identified febrile neutropenia as the independent factor influencing vancomycin concentration/dose ratio and clearance only in pediatric patients aged 1-6 years.

CONCLUSIONS

Increased initial dosage and therapeutic drug monitoring-guided dose optimization are critical for the therapeutic efficacy of vancomycin in pediatric patients with febrile neutropenia, especially in those aged 1-6 years.

Applicability of vancomycin, meropenem, and linezolid in capillary microsamples vs. dried blood spots: A pilot study for microsampling in critically ill children

INTRODUCTION

Therapeutic drug monitoring (TDM) has been shown to be clinically beneficial for critically ill patients. However, this is a burden for neonates or children with small circulating blood volumes. Here, we aimed to develop and validate a microsampling TDM platform (including dried blood spots (DBS) and capillary microsamples (CMS)) for the simultaneous quantification of vancomycin, meropenem, and linezolid.

METHODS

Paired DBS and CMS samples were obtained from an intensive care unit (ICU) to evaluate its clinical application. Estimated plasma concentrations (EPC) were calculated from DBS concentrations. Agreement between methods was evaluated using Deming regression and Bland-Altman difference plots.

RESULTS

The microsampling methods validation showed excellent reliability and compatibility with the analysis of the sample matrix and hematocrit range of the studied population. The DBS and CMS accuracy and precision results were within accepted ranges and samples were stable at room temperature for at least 2 days and 8 h, respectively. Hematocrit had no impact on CMS, but sightly impacted DBS measurements. The CMS and DBS antibiotic concentrations correlated well (r > 0.98). The drug concentration ratio in DBS samples to that in CMS was 1.39 for vancomycin, 1.34 for meropenem, and 0.94 for linezolid. The EPC calculated from the DBS using individual hematocrit ranges presented comparable absolute values for vancomycin (slope: 1.06) and meropenem (slope: 1.04), with a mean of 98% and 99% of the measured CMS concentrations, respectively.

DISCUSSION

This study provides a microsampling TDM platform validated for clinical use for a rapid quantification of three antibiotics and is suitable for real-time TDM-guided personalization of antimicrobial treatment in critically ill children.

Precision dosing of vancomycin: in defence of AUC-guided therapy in children

In 2020, new vancomycin guidelines were released, recommending the transition from trough-based to AUC24 monitoring for adult and paediatric patients. Given the resources required to achieve this transition, there has been debate about the costs and benefits of AUC24-based monitoring. A recent narrative review of vancomycin therapeutic drug monitoring in paediatrics claims to have uncovered the methodological weaknesses of the data that informed the guidelines and advises against premature adoption of AUC24-guided monitoring. In this article, we present supporting arguments for AUC24-guided monitoring in children, which include that: (i) troughs alone are inadequate surrogates for AUC24; (ii) vancomycin-associated nephrotoxicity has significant consequences that warrant optimization of dosing; (iii) a substantial portion of children receiving vancomycin are at high risk for poor outcomes and deserve targeted monitoring; and (iv) limited efficacy data in support of AUC24 is not a justification to revert to a less supported monitoring approach.