The kinetic profile of vancomycin in neonates

Optimization of Vancomycin Initial Dosing Regimen in Neonates Using an Externally Evaluated Population Pharmacokinetic Model

BACKGROUND

Vancomycin therapeutic monitoring guidelines were revised in March 2020, and a population pharmacokinetics-guided Bayesian approach to estimate the 24-hour area under the concentration-time curve to the minimum inhibitory concentration ratio has since been recommended instead of trough concentrations. To comply with these latest guidelines, we evaluated published population pharmacokinetic models of vancomycin using an external dataset of neonatal patients and selected the most predictive model to develop a new initial dosing regimen.

METHODS

The models were identified from the literature and tested using a retrospective dataset of Canadian neonates. Their predictive performance was assessed using prediction- and simulation-based diagnostics. Monte Carlo simulations were performed to develop the initial dosing regimen with the highest probability of therapeutic target attainment.

RESULTS

A total of 144 vancomycin concentrations were derived from 63 neonates in the external population. Five of the 28 models retained for evaluation were found predictive with a bias of 15% and an imprecision of 30%. Overall, the Grimsley and Thomson model performed best, with a bias of -0.8% and an imprecision of 20.9%; therefore, it was applied in the simulations. A novel initial dosing regimen of 15 mg/kg, followed by 11 mg/kg every 8 hours should favor therapeutic target attainment.

CONCLUSIONS

A predictive population pharmacokinetic model of vancomycin was identified after an external evaluation and used to recommend a novel initial dosing regimen. The implementation of these model-based tools may guide physicians in selecting the most appropriate initial vancomycin dose, leading to improved clinical outcomes.

Bayesian Vancomycin Model Selection for Therapeutic Drug Monitoring in Neonates

BACKGROUND AND OBJECTIVE

Pharmacokinetic models can inform drug dosing of vancomycin in neonates to optimize therapy. However, the model selected needs to describe the intended population to provide appropriate dose recommendations. Our study aims to identify the population pharmacokinetic (PopPK) model(s) with the best performance to predict vancomycin exposure in neonates in our hospital.

METHODS

Relevant published PopPK models for vancomycin in neonates were selected based on demographics and vancomycin dosing strategy. The predictive performance of the models was evaluated in Tucuxi using a local cohort of 69 neonates. Mean absolute error (MAE), relative bias (rBias) and relative root mean square error (rRMSE) were used to quantify the accuracy and precision of the predictive performance of each model for three different approaches: a priori, a posteriori, and Bayesian forecasting for the next course of therapy based on the previous course predictions. A PopPK model was considered clinically acceptable if rBias was between ± 20 and 95% confidence intervals included zero.

RESULTS

A total of 25 PopPK models were identified and nine were considered suitable for further evaluation. The model of De Cock et al. 2014 was the only clinically acceptable model based on a priori [MAE 0.35 mg/L, rBias 0.8 % (95% confidence interval (CI) - 7.5, 9.1%), and rRMSE 8.9%], a posteriori [MAE 0.037 mg/L, rBias - 0.23% (95% CI - 1.3, 0.88%), and rRMSE 6.02%] and Bayesian forecasting for the next courses [MAE 0.89 mg/L, rBias 5.45% (95% CI - 8.2, 19.1%), and rRMSE 38.3%) approaches.

CONCLUSIONS

The De Cock model was selected based on a comprehensive approach of model selection to individualize vancomycin dosing in our neonates.

Population Pharmacokinetic Models of Vancomycin in Paediatric Patients: A Systematic Review

BACKGROUND

Vancomycin is commonly used to treat gram-positive bacterial infections in the paediatric population, but dosing can be challenging. Population pharmacokinetic (popPK) modelling can improve individualization of dosing regimens. The primary objective of this study was to describe popPK models of vancomycin and factors that influence pharmacokinetic (PK) variability in paediatric patients.

METHODS

Systematic searches were conducted in the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, International Pharmaceutical Abstracts and the grey literature without language or publication status restrictions from inception to 17 August 2020. Observational studies that described the development of popPK models of vancomycin in paediatric patients (< 18 years of age) were included. Risk of bias was assessed using the National Heart, Lung and Blood Institute Study Quality Assessment Tool for Case Series Studies.

RESULTS

Sixty-four observational studies (1 randomized controlled trial, 13 prospective studies and 50 retrospective studies of 9019 patients with at least 25,769 serum vancomycin concentrations) were included. The mean age was 2.5 years (range 1 day-18 years), serum creatinine was 47.1 ± 33.6 µmol/L, and estimated creatinine clearance was 97.4 ± 76 mL/min/1.73m². Most studies found that vancomycin PK was best described by a one-compartment model (71.9%). There was a wide range of clearance and volume of distribution (V_d) values (range 0.014-0.27 L/kg/h and 0.43-1.46 L/kg, respectively) with interindividual variability as high as 49.7% for clearance and 136% for V_d, proportional residual variability up to 37.5% and additive residual variability up to 17.5 mg/L. The most significant covariates for clearance were weight, age, and serum creatinine or creatinine clearance, and weight for V_d. Variable dosing recommendations were suggested.

CONCLUSION

Numerous popPK models of vancomycin were derived, however external validation of suggested dosing regimens and analyses in subgroup paediatric populations such as dialysis patients are still needed before a popPK model with best predictive performance can be applied for dosing recommendations. Significant intraindividual and interindividual PK variability was present, which demonstrated the need for ongoing therapeutic drug monitoring and derivation of PK models for vancomycin for certain subgroup populations, such as dialysis patients.

Larger Dose Reductions of Vancomycin Required in Neonates with Patent Ductus Arteriosus Receiving Indomethacin versus Ibuprofen

Ibuprofen and indomethacin are commonly used to induce ductus arteriosus closure in preterm neonates. Our group previously reported that ibuprofen decreased vancomycin clearance by 16%. In this study, we quantified the impact of indomethacin coadministration on vancomycin clearance by extending our vancomycin population pharmacokinetic model with a data set containing vancomycin concentrations measured in preterm neonates comedicated with indomethacin. The modeling data set includes concentration-time data of vancomycin administered alone or in combination with either ibuprofen or indomethacin collected in the neonatal intensive care units of UZ Leuven (Leuven, Belgium) and São Francisco Xavier Hospital (Lisbon, Portugal). The derived vancomycin pharmacokinetic model was subsequently used to propose dose adjustments that yield effective vancomycin exposure (i.e., area under the concentration-time curve from 0 to 24 h [AUC_0-24] between 300 to 550 mg·h/liter, with a probability of <0.1 of subtherapeutic exposure) in preterm neonates with patent ductus arteriosus. We found that indomethacin coadministration reduced vancomycin clearance by 55%. Model simulations showed that the most recent vancomycin dosing regimen, which was based on an externally validated model, requires 20% and 60% decreases of the loading and maintenance doses of vancomycin, respectively, when aiming for optimized exposure in the neonatal population. By analyzing vancomycin data from preterm neonates comedicated with indomethacin, we found a substantial decrease in vancomycin clearance of 55% versus a previously reported 16% for ibuprofen. This decrease in clearance impacts vancomycin dosing, and we anticipate that other drugs eliminated by glomerular filtration are likely to be affected to a similar extent as vancomycin.

Renal Function Descriptors in Neonates: Which Creatinine-Based Formula Best Describes Vancomycin Clearance?

Growth and maturational changes have been identified as significant covariates in describing variability in clearance of renally excreted drugs such as vancomycin. Because of immaturity of clearance mechanisms, quantification of renal function in neonates is of importance. Several serum creatinine (SCr)-based renal function descriptors have been developed in adults and children, but none are selectively derived for neonates. This review summarizes development of the neonatal kidney and discusses assessment of the renal function regarding estimation of glomerular filtration rate using renal function descriptors. Furthermore, identification of the renal function descriptors that best describe the variability of vancomycin clearance was performed in a sample study of a septic neonatal cohort. Population pharmacokinetic models were developed applying a combination of age-weight, renal function descriptors, or SCr alone. In addition to age and weight, SCr or renal function descriptors significantly reduced variability of vancomycin clearance. The population pharmacokinetic models with Léger and modified Schwartz formulas were selected as the optimal final models, although the other renal function descriptors and SCr provided reasonably good fit to the data, suggesting further evaluation of the final models using external data sets and cross validation. The present study supports incorporation of renal function descriptors in the estimation of vancomycin clearance in neonates.

External Evaluation of Population Pharmacokinetic Models of Vancomycin in Neonates: The transferability of published models to different clinical settings

BACKGROUND

Vancomycin is one of the most evaluated antibiotics in neonates using modeling and simulation approaches. However no clear consensus on optimal dosing has been achieved. The objective of the present study was to perform an external evaluation of published models, in order to test their predictive performances in an independent dataset and to identify the possible study-related factors influencing the transferability of pharmacokinetic models to different clinical settings.

METHOD

Published neonatal vancomycin pharmacokinetic models were screened from the literature. The predictive performance of 6 models was evaluated using an independent dataset (112 concentrations from 78 neonates). The evaluation procedures used simulation-based diagnostics (visual predictive check [VPC] and normalized prediction distribution errors [NPDE]).

RESULTS

Differences in predictive performances of models for vancomycin pharmacokinetics in neonates were found. The mean of NPDE for 6 evaluated models were 1.35, -0.22, -0.36, 0.24, 0.66, 0.48, respectively. These differences were explained, at least partly, by taking into account the method used to measure serum creatinine concentrations. The adult conversion factor of 1.3 (enzymatic to Jaffé) was tested with an improvement in the VPC and NPDE, but it still need to be evaluated and validated in neonates. Differences were also identified between analytical methods for vancomycin.

CONCLUSION

The importance of analytical techniques for serum creatinine concentrations and vancomycin as a predictor of vancomycin concentrations in neonates has been confirmed. Dosage individualisation of vancomycin in neonates should consider not only patients' characteristics and clinical conditions, but also the methods used to measure serum creatinine and vancomycin.

Optimization of vancomycin dosing in very low-birth-weight preterm neonates

OBJECTIVE

To compare vancomycin serum trough concentrations and 24-hour area under the serum concentration-versus-time curve (AUC24) among very low-birth-weight (VLBW) premature infants before and after implementation of an institution-wide increase in neonatal vancomycin dosing.

STUDY DESIGN

We performed a retrospective analysis of vancomycin concentrations among preterm VLBW neonates before (2007-2010) and after (2010-2013) implementation of a new vancomycin dosing protocol consisting of increased vancomycin daily dose and frequency of administration.

RESULTS

Neonates weighing < 1,500 g and receiving the new vancomycin dosing regimen had lower rates of undetectable trough concentrations (24 vs. 50%, p = 0.04), higher median trough concentrations (10.8 vs. 5.9 µg/mL, p = 0.003), a higher proportion of goal trough concentrations of 10 to 20 µg/mL (35 vs. 4%, p = 0.005), and a significantly higher vancomycin AUC24 (438 vs. 320 mg·h/L, p = 0.004) compared with historical controls.

CONCLUSION

Increasing the vancomycin daily dose and dosing frequency led to an increase in vancomycin trough concentrations and AUC24, and a decrease in the proportion of undetectable (< 5.0 µg/mL) troughs, without an increase in toxicity among VLBW premature neonates.

Population pharmacokinetic analysis during the first 2 years of life: an overview

Three decades after its introduction, pharmacokinetic population approaches have become a reference method for drug modelling, particularly in paediatrics. The main practical limitation in this specific population is the collected blood volume. Pharmacokinetic population approaches using sparse sampling may resolve this issue. The pharmacokinetics of many drugs have been studied during the last 25 years using such methods. This review summarizes all of the published studies concerning population pharmacokinetic approaches in paediatric subjects from neonate to 2 years old. A literature search was conducted using the PubMed database, from 1985 to December 2010, using the following terms: pharmacokinetic(s), population, paediatric/pediatric and neonate(s). Articles were excluded if they were not pertinent according to our criteria. References of all relevant articles were also evaluated. Ninety-eight studies were included in this review. The following information was extracted from the articles: drug name, therapeutic class, population size, age of patients, number of samples per patient, covariates used for clearance and volume of distribution estimates, software used for modelling and validation methods. An increasing rate of publications over the years was observed; 44 different drugs were studied using a pharmacokinetic population approach. Antibacterials were the most studied class of drugs, including a large number of studies devoted to vancomycin and gentamicin. It must be underlined that few studies have been performed on anticonvulsant drugs and anaesthetics used in clinical daily practice conditions.

Clinical pharmacokinetics of vancomycin in the neonate: a review

Neonatal sepsis is common and is a major cause of morbidity and mortality. Vancomycin is the preferred treatment of several neonatal staphylococcal infections. The aim of this study was to review published data on vancomycin pharmacokinetics in neonates and to provide a critical analysis of the literature. A bibliographic search was performed using PubMed and Embase, and articles with a publication date of August 2011 or earlier were included in the analysis. Vancomycin pharmacokinetic estimates, which are different in neonates compared with adults, also exhibit extensive inter-neonatal variability. In neonates, several vancomycin dosing schedules have been proposed, mainly based on age (i.e., postmenstrual and postnatal), body weight or serum creatinine level. Other covariates [e.g., extracorporeal membrane oxygenation (ECMO), indomethacin or ibuprofen, and growth restriction] of vancomycin pharmacokinetics have been reported in neonates. Finally, vancomycin penetrates cerebrospinal fluid (range = 7-42%). Renal function drives vancomycin pharmacokinetics. Because either age or weight is the most relevant covariate of renal maturation, these covariates should be considered first in neonatal vancomycin dosing guidelines and further adjusted by renal dysfunction indicators (e.g., ECMO and ibuprofen/indomethacin). In addition to the prospective validation of available dosing guidelines, future studies should focus on the relevance of therapeutic drug monitoring and on the value of continuous vancomycin administration in neonates.

Vancomycin: a review of population pharmacokinetic analyses

Despite nearly five decades of clinical use, vancomycin has retained a significant and uncontested niche in the antibacterial arsenal because of its consistent activity against almost all Gram-positive bacteria. Nevertheless, major vancomycin toxicities have been reported in the literature - in particular, nephrotoxicity and ototoxicity. Vancomycin pharmacokinetics have been described in numerous studies for 25 years. This review presents a synthesis of the reported population pharmacokinetic models of vancomycin. The objective was to determine if there was a consensus on a structural model and which covariates were identified. A literature search was conducted from the PubMed database, from its inception through December 2010, using the following terms: 'vancomycin', 'pharmacokinetic(s)', 'population', 'model(ling)' and 'nonlinear mixed effect'. Articles were excluded if they were not pertinent. The reference lists of all selected articles were also evaluated. Twenty-five articles were included in this review: 15 models concerned paediatric patients and ten models were conducted in adults. In neonates and infants, the pharmacokinetics of vancomycin were mainly described by a one-compartment model, whereas in adults, a two-compartment model was preferentially used. Various covariates were tested but only three (age, creatinine clearance [CL(CR)] and body weight) were included in almost all of the described models. After inclusion of these covariates, the mean (range) values of the interindividual variability in the clearance and volume of distribution were 30% (15.6-45%) and 23% (12.6-48%), respectively. The mean (range) value of the residual variability was 20% (7-39.6%). This review highlights the numerous population pharmacokinetic models of vancomycin developed in recent decades and concludes with relevant information for clinicians and researchers. To optimize vancomycin dosage, this review points out the relevant covariates according to the target population. In adults, dosage optimization depends on CL(CR) and body weight, while in children, it depends on age, body weight and CL(CR). For future population pharmacokinetic studies, a sensitive liquid chromatography-tandem mass spectrometry method could be used and new covariates such as cardiac output or possible renal transporters could be tested. Finally, we suggest that external evaluation should be the first step in a pharmacokinetic analysis of vancomycin rather than describing a new model.

Evaluation of the vancomycin dosage regimen based on serum creatinine used in the neonatal intensive care unit

BACKGROUND

Vancomycin is frequently used for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections; however, determining the optimal dosage for neonates is difficult because of their immature renal function.

METHODS

Serum creatinine-based dosing was introduced in Kumamoto City Hospital Neonatal Medical Center. Serum trough concentration and therapeutic efficacy of vancomycin were evaluated before and after the introduction of the creatinine-based dosing.

RESULTS

When the therapeutic range of serum trough concentration of vancomycin at steady state was set to 5-15 µg/mL, 20 trough concentrations (48.8%) were within the therapeutic range and 21 trough concentrations were outside the therapeutic range before the introduction of the serum creatinine-based dosing. After the introduction of serum creatinine-based dosing, 18 trough concentrations (81.8%) were within the therapeutic range and 4 trough concentrations were not, and there was an increase in the number of patients with trough concentrations in the therapeutic range (P= 0.01; Fisher's exact test).

CONCLUSIONS

The serum creatinine-based dosing of vancomycin is useful in maintaining the appropriate serum level of vancomycin in neonates.

The impact of ibuprofen or indomethacin on renal drug clearance in neonates

INTRODUCTION

Administration of ibuprofen or indomethacin in neonates is associated with a reduction of glomerular filtration, reflected in a reduction in the elimination of drugs dependent on renal function for clearance. However, the magnitude of these effects and potential differences between ibuprofen or indomethacin remain unclear.

METHODS

Observations collected in two population pharmacokinetic studies in preterm neonates investigating amikacin and vancomycin disposition were used to estimate (i) the impact of ibuprofen administration and (ii) the difference between ibuprofen and indomethacin on renal drug clearance.

RESULTS

Amikacin clearance was reduced by 21% and vancomcyin was reduced by 18% during co-administration of ibuprofen. In a vancomycin pooled pharmacokinetic study, it was documented that the impact of indomethacin was significantly higher compared to ibuprofen (46 and 28%, respectively).

CONCLUSIONS

Both ibuprofen and indomethacin have a quantifiable impact on renal drug clearance. Compared to ibuprofen, the impact of indomethacin is more pronounced. Population modelling with covariate analysis can be a tool to disentangle the impact of various covariates, including ibuprofen or indomethacin, on renal drug clearance.

[Design and validation of a dosing algorithm for vancomycin in premature neonates]

INTRODUCTION

Inappropriate use of vancomycin contributes to the development of resistant bacteria and jeopardizes the safety and effectiveness of treatment. The aim of this article was to design and validate an empirical dosing algorithm for vancomycin in premature neonates according to their population-based pharmacokinetic characteristics.

PATIENTS AND METHODS

We performed a retrospective analysis of 129 serum samples from a cohort of 53 neonates. Homogeneous population groups were identified both from their individual pharmacokinetic parameters and from their biometric characteristics. The design of the dosing algorithm was based on simulation of the serum vancomycin concentration that would be reached with several different doses. The algorithm was validated in another cohort of 30 neonates and 108 serum samples.

RESULTS

Introduction of the algorithm significantly increased the percentage initial values obtained with correct minimum and maximum concentrations in the first monitoring round (p<0.05). The mean number of serum samples obtained per patient for treatment monitoring was significantly reduced (3.6+/-2 vs. 4.9+/-3).

CONCLUSIONS

The implantation of the dosing algorithm for vancomycin in premature neonates increased the efficiency of treatment, reduced monitoring requirements, and optimized serum vancomycin concentrations from the start of treatment.

Vancomycin

This review describes the use of vancomycin in neonates over the last three decades. Given the relation of late-onset neonatal septicaemia to outcome and the increase in coagulase-negative staphylococcal infection as causative organism, vancomycin remains an important antibacterial in the neonatal intensive care unit. The pharmacokinetic behaviour of vancomycin in neonates can be adequately described by a one- or two-compartment model and is mainly determined by postconceptional age and renal function. In neonates, a patent ductus arteriosus as well as treatment with indomethacin or extracorporeal membrane oxygenation (ECMO) leads to an increase in volume of distribution and a decrease in clearance. Microbiological studies in vitro have shown that an increase in vancomycin concentrations above the minimum inhibitory concentration does not result in more effective killing. The microbiological and clinical efficacy of vancomycin in neonates has only been studied explicitly in a restricted number of patients. There are no definitive data relating serum concentrations to effect in this patient group. Vancomycin-related nephrotoxicity and ototoxicity in neonates is rare, and no clear relation to serum concentrations has been demonstrated. Based on the pharmacokinetic profile of vancomycin in neonates, several administration regimens have been constructed. Recent guidelines have suggested that dosage can be independent of gestational age or postconceptional age in neonates without renal failure. In patients with renal failure, therapy can be adequately tailored by using a regimen based on serum creatinine. The usefulness of routine monitoring of peak serum concentrations is doubtful based on the current literature. Recent research demonstrates a shift towards taking only routine trough serum concentrations in order to optimise efficacy. Patients with renal failure and other special subpopulations, such as patients exposed to ECMO or indomethacin, need to be monitored more closely.

Dose regimen for vancomycin not needing serum peak levels?

AIM

To determine the safety, efficacy, and need to measure peak serum vancomycin concentrations in a neonatal population using a standard vancomycin dosage regimen.

METHOD

A total of 101 infants who were admitted to a regional neonatal intensive care unit and received vancomycin (15 mg/kg every 12 or 18 hours depending on postnatal age) were studied retrospectively. Infants who had been started on vancomycin before they were transferred to the unit were excluded. The proportion of infants was measured whose serum vancomycin concentrations were within a conservative therapeutic range of trough 5-10 mg/l, peak 20-40 mg/l, and a less conservative, but still safe, range of trough 5-12 mg/l, peak 15-60 mg/l.

RESULTS

Trough concentrations of 5-10 mg/l were achieved by 46.5% of infants, and 5-12 mg/l by 55.4%. Peak concentrations of 20-40 mg/l were found in 83.2% of infants, and 15-60 mg/l in 99.0%. Highest peak concentration was 47.2 mg/l. Some 89.4% of infants with trough concentrations of 5-10 mg/l had a peak concentration of 20-40 mg/l.

CONCLUSIONS

The vancomycin dosage regimen used in this study produces acceptable therapeutic serum vancomycin concentrations. Peak serum vancomycin concentrations do not need to be measured in neonates using this dosage regimen.