Population pharmacokinetic analysis of vancomycin in pediatric continuous renal replacement therapy

A Review of Vancomycin, Gentamicin, and Amikacin Population Pharmacokinetic Models in Neonates and Infants

Population pharmacokinetic (popPK) models are an essential tool when implementing therapeutic drug monitoring (TDM) and to overcome dosing challenges in neonates in clinical practice. Since vancomycin, gentamicin, and amikacin are among the most prescribed antibiotics for the neonatal population, we aimed to characterize the popPK models of these antibiotics and the covariates that may influence the pharmacokinetic parameters in neonates and infants with no previous pathologies. We searched the PubMed, Embase, Web of Science, and Scopus databases and the bibliographies of relevant articles from inception to the beginning of February 2024. The search identified 2064 articles, of which 68 met the inclusion criteria (34 for vancomycin, 21 for gentamicin, 13 for amikacin). A one-compartment popPK model was more frequently used to describe the pharmacokinetics of the three antibiotics (91.2% vancomycin, 76.9% gentamicin, 57.1% amikacin). Pharmacokinetic parameter (mean ± standard deviation) values calculated for a "typical" neonate weighing 3 kg were as follows: clearance (CL) 0.34 ± 0.80 L/h for vancomycin, 0.27 ± 0.49 L/h for gentamicin, and 0.19 ± 0.07 L/h for amikacin; volume of distribution (Vd): 1.75 ± 0.65 L for vancomycin, 1.54 ± 0.53 L for gentamicin, and 1.67 ± 0.27 L for amikacin for one-compartment models. Total body weight, postmenstrual age, and serum creatinine were common predictors (covariates) for describing the variability in CL, whereas only total body weight predominated for Vd. A single universal popPK model for each of the antibiotics reviewed cannot be implemented in the neonatal population because of the significant variability between them. Body weight, renal function, and postmenstrual age are important predictors of CL in the three antibiotics, and total body weight for Vd. TDM represents an essential tool in this population, not only to avoid toxicity but to attain the desired pharmacokinetic/pharmacodynamic index. The characteristics of the neonatal population, coupled with the lack of prospective studies and external validation of most models, indicate a need to continue investigating the pharmacokinetics of these antibiotics in neonates.

Drug dosing optimization in critically ill children under continuous renal replacement therapy: from basic concepts to the bedside model informed precision dosing

INTRODUCTION

Optimizing drug dosage in critically ill children undergoing Continuous Renal Replacement Therapy (CRRT) is mandatory and challenging, given the many factors impacting pharmacokinetics and pharmacodynamics coupled with the vulnerability of this population.

AREAS COVERED

A good understanding of the mechanisms that determine drug elimination via the CRRT technique is useful to avoid prescription pitfalls, however limited by the high between and within subject variability. The developments of population pharmacokinetic and physiologically based pharmacokinetic models derived from in-vivo and in-vitro studies, are challenging, but remain the most appropriate tool to suggest adjusted dosage regimens for every patient, throughout treatment. We searched PubMed using the search string: 'pediatrics OR children' AN 'continuous renal replacement therapy' AND 'pharmacokinetics' AND 'model informed precision dosing' AND, 'physiologically based pharmacokinetics,' AND 'therapeutic drug monitoring' until January 2024, regardless of language or publication status.

EXPERT OPINION

Familiarizing the pediatric intensivists with the therapeutic drug monitoring and providing clinicians the individualized prescribing software such as Model Informed Precision Dosing would be a significant step forward. The clinical benefit for patients remains to be demonstrated.

The impact of extracorporeal support on antimicrobial pharmacokinetics in critically ill neonatal and paediatric patients: A systematic review

OBJECTIVES

Infections represent a major risk for critically ill neonatal and paediatric patients requiring extracorporeal life-saving support such as extracorporeal membrane oxygenation (ECMO) and/or continuous renal replacement therapies (CRRT). Patient outcomes rely on achieving target antimicrobial concentrations. In critically ill adults on extracorporeal support, suboptimal antimicrobial concentrations have been shown to be common. Our objective was to systematically review antimicrobial pharmacokinetic studies in critically ill term neonatal and paediatric patients receiving ECMO and/or CRRT and compare them to similar cohorts of patients not receiving ECMO or CRRT.

METHODS

Studies published between 1990 and 2022 were identified through systematic searches in PUBMED, Embase, Web of Science, Medline, Google Scholar and CINAHL. Studies were included which provided antimicrobial pharmacokinetic parameters (volume of distribution and clearance) in the neonatal and paediatric patients receiving ECMO and/or CRRT. Studies were excluded if no antimicrobial pharmacokinetic parameters were described or could be calculated.

RESULTS

Forty-four pharmacokinetic studies were identified describing 737 patients, with neonatal patients recruited in 70% of the ECMO studies and <1% of the CRRT studies. Of all the studies, 50% were case reports or case series. The pharmacokinetics were altered for gentamicin, daptomycin, ceftolozane, micafungin, voriconazole, cefepime, fluconazole, piperacillin, and vancomycin, although considerable patient variability was described.

CONCLUSION

Significant gaps remain in our understanding of the pharmacokinetic alterations in neonatal and paediatric patients receiving ECMO and CRRT support.

Dose optimization and target attainment of vancomycin in children

Vancomycin is a glycopeptide antibiotic that has been adopted in clinical practice to treat gram-positive infections for more than 70 years. Despite vancomycin's long history of therapeutic use, optimal dose adjustments and pharmacokinetic/pharmacodynamic (PK/PD) target attainment in children are still under debate. Therapeutic drug monitoring (TDM) has been widely integrated into pediatric clinical practice to maximize efficacy and safety of vancomycin treatment. Area under the curve (AUC)-guided TDM has been recently recommended instead of trough-only TDM to ensure PK/PD target attainment of AUC0-24h/minimal inhibitory concentration (MIC) > 400 to 600 and minimize acute kidney injury risk. Bayesian forecasting in pediatric patients allows estimation of population PK to accurately predict individual vancomycin concentrations over time, and consequently total vancomycin exposure. AUC-guided TDM for vancomycin, preferably with Bayesian forecasting, is therefore suggested for all pediatric age groups and special pediatric populations. In this review we aim to analyze the current literature on the pediatric use of vancomycin and summarize the current knowledge on dosing optimization for target attainment in special patient populations.

Cefepime pharmacokinetics in critically ill children and young adults undergoing continuous kidney replacement therapy

OBJECTIVES

Cefepime is an antibiotic commonly used to treat sepsis and is cleared by renal excretion. Cefepime dosing requires adjustment in patients with decreased kidney function and in those receiving continuous kidney replacement therapy (CKRT). We aimed to characterize cefepime PK in a diverse cohort of critically ill paediatric patients on CKRT.

METHODS

Patients were identified from an ongoing pharmacokinetic/pharmacodynamic (PK/PD) study of beta-lactam antibiotics, and were included if they had received at least two cefepime doses in the ICU and were on CKRT for at least 24 h. PK parameters were estimated using MwPharm++ with Bayesian estimation and a paediatric population PK model. Target attainment was assessed as time of free cefepime concentrations above minimum inhibitory concentration (fT > 1× or 4 × MIC).

RESULTS

Seven patients were included in the study (ages 2 to 20 years). CKRT indications included liver failure (n = 1), renal failure (n = 4) and fluid overload (n = 2). Total effluent flow rates ranged from 1833 to 3115 (mean 2603) mL/1.73 m2/h, while clearance was 2.11-3.70 (mean 3.0) L/h/70 kg. Effluent flows were lower, but clearance and fT > MIC were similar to paediatric data published previously. Using Pseudomonas aeruginosa MIC breakpoints, all patients had 100% of dosing interval above MIC, but only one had 100% of dosing interval above 4× MIC.

CONCLUSIONS

Since most patients failed to attain stringent targets of 100% fT > 4×  MIC, model-informed precision dosing may benefit such patients.

Evaluation of Dosing Regimens of Vancomycin and Aminoglycosides in Pediatric Patients on Continuous Renal Replacement Therapy

OBJECTIVE

To determine the optimal empiric dosing regimen to achieve therapeutic serum concentrations of vancomycin and aminoglycosides in pediatric patients who are receiving continuous renal replacement therapy (CRRT).

METHODS

This retrospective study investigated pediatric patients (<18 years old) who received at least one dose of an aminoglycoside and/or vancomycin while on CRRT and who had at least one serum concentration assessed during the study period. Rates of culture clearance and discontinuation of renal replacement therapy, pharmacokinetic variables (i.e., volume of distribution [Vd], half-life [t½], rate of elimination [ke]), and correlations between patient's age and weight in regard to the empiric dosing regimen were evaluated.

RESULTS

Forty-three patients were included in this study. The median dose required to reach therapeutic serum concentrations for vancomycin was 17.6 mg/kg (12.8-20.4 mg/kg) every 12 hours (6-30 hours) in continuous venovenous hemodialysis (CVVHD) patients and 16.3 mg/kg (13.9-21.4 mg/kg) every 12 hours (6-24 hours) in continuous venovenous hemodiafiltration (CVVHDF) patients. The median dose for aminoglycosides was unable to be determined. In CVVHD patients, the median vancomycin ke was 0.04 hr^-1, t½ was 18 hours, and Vd was 1.6 L/kg. In CVVHDF patients, the median vancomycin ke was 0.05 hr^-1, t½ was 14 hours, and Vd was 0.6 L/kg. No correlation was found between age and weight with regard to effective dosing regimen.

CONCLUSIONS

To achieve therapeutic trough concentrations in pediatric patients on CRRT, vancomycin should be dosed at approximately 17.5 mg/kg administered every 12 hours.

Population Pharmacokinetics and Pharmacodynamics of Vancomycin in Pediatric Patients With Various Degrees of Renal Function

OBJECTIVE

Although vancomycin dosage recommendations in the pediatric setting for methicillin-resistant Staphylococcus aureus (MRSA) infection indicate that ≥60 mg/kg/day is correlated to a desired area under the vancomycin concentration time curve from 0 to 24 hours to minimum inhibitory concentration ratio (AUC0–24 hr/MIC) ≥400, for some patients this dosage is inadequate or relates to toxicity. This study purposed to explore vancomycin dosing for pediatrics with various degrees of renal function.

METHODS

Routine monitoring data were retrospectively collected from patients, aged 1 month to 18 years. Population pharmacokinetic analysis was performed by using non-linear mixed-effect model with NONMEM software, and Monte Carlo simulation was conducted by using Crystal Ball software.

RESULTS

Two hundred twelve patients with 348 vancomycin serum concentrations were included. Median age was 3.5 years (IQR, 0.9–10.9), median weight was 14.0 kg (IQR, 7.2–30.4), with baseline estimated glomerular filtration rate (eGFR) ranging from 15.5 to 359.3 mL/min/1.73 m2. A 1-compartment model with first-order elimination sufficiently described vancomycin PK. The dosing targeting AUC0–24hr/MIC ≥400 and AUC0–24hr &lt;800 mg•h/L for pediatric patients with eGFRs of 15 to 29, 30 to 59, 60 to 89, 90 to 129, and 130 to 160 mL/min/1.73 m2 was 12.5, 25, 40, 60, and 70 mg/kg/day, respectively. All vancomycin dosing obtained &gt;85% of the cumulative fraction of response across the MIC distribution of MRSA.

CONCLUSIONS

Vancomycin dosing of 12.5, 25, 40, 60, and 70 mg/kg/day is suggested for pediatric patients with eGFRs of 15 to 29, 30 to 59, 60 to 89, 90 to 129, and 130 to 160 mL/min/1.73 m2, respectively.

Implementation of Vancomycin Therapeutic Monitoring Guidelines: Focus on Bayesian Estimation Tools in Neonatal and Pediatric Patients

BACKGROUND

The 2020 consensus guidelines for vancomycin therapeutic monitoring recommend using Bayesian estimation targeting the ratio of the area under the curve over 24 hours to minimum inhibitory concentration as an optimal approach to individualize therapy in pediatric patients. To support institutional guideline implementation in children, the objective of this study was to comprehensively assess and compare published population-based pharmacokinetic (PK) vancomycin models and available Bayesian estimation tools, specific to neonatal and pediatric patients.

METHODS

PubMed and Embase databases were searched from January 1994 to December 2020 for studies in which a vancomycin population PK model was developed to determine clearance and volume of distribution in neonatal and pediatric populations. Available Bayesian software programs were identified and assessed from published articles, software program websites, and direct communication with the software company. In the present review, 14 neonatal and 20 pediatric models were included. Six programs (Adult and Pediatric Kinetics, BestDose, DoseMeRx, InsightRx, MwPharm++, and PrecisePK) were evaluated.

RESULTS

Among neonatal models, Frymoyer et al and Capparelli et al used the largest PK samples to generate their models, which were externally validated. Among the pediatric models, Le et al used the largest sample size, with multiple external validations. Of the Bayesian programs, DoseMeRx, InsightRx, and PrecisePK used clinically validated neonatal and pediatric models.

CONCLUSIONS

To optimize vancomycin use in neonatal and pediatric patients, clinicians should focus on selecting a model that best fits their patient population and use Bayesian estimation tools for therapeutic area under the -curve-targeted dosing and monitoring.

Determinants of Vancomycin Trough Concentration in Patients Receiving Continuous Veno-Venous Hemodialysis

BACKGROUND

Vancomycin pharmacokinetics are altered in the critically ill and are further distorted by renal replacement therapy. Limited literature is available evaluating vancomycin dosing in continuous veno-venous hemodialysis (CVVHD).

OBJECTIVE

The goal of this analysis was to identify factors that affect vancomycin trough concentration in patients on CVVHD and to determine an appropriate dosing strategy.

METHODS

This was a single-center, retrospective cohort study of adult inpatients admitted to the Cleveland Clinic from May 2016-December 2017. Patients in the intensive care unit who received ≥ 2 doses of vancomycin during CVVHD were included. Patients with interruptions of CVVHD inappropriately timed troughs, a change in dialysate rate, and those who received different vancomycin dosages were excluded. Multivariable linear regression including age, sex, weight, Sequential Organ Failure Assessment score, albumin, 24-hour urine output (UOP), dialysate rate, filter type, and vancomycin dose was run to determine predictors of vancomycin concentration.

RESULTS

A total of 160 patients were included. The median vancomycin dose was 12.6 mg/kg with a trough of 24.6 mcg/mL. Weight, 24-hour UOP, vancomycin dose (mg/kg), and dialysate rate (mL/kg/h) were all determined to be independent predictors of vancomycin trough level. Patients who received <10 mg/kg doses of vancomycin (N=18) achieved a median trough of 21.5 mcg/mL, with 83% being therapuetic. In patients who received >10 mg/kg (N=142), the median trough was 25.5 mcg/mL, with 47% being therapeutic.

CONCLUSION AND RELEVANCE

Vancomycin dose, dialysate rate, UOP, and weight are independently associated with vancomycin trough concentration. In CVVHD patients, vancomycin dosed at 10 mg/kg every 24 hours may be an appropriate recommendation.

Pharmacokinetics of Commonly Used Medications in Children Receiving Continuous Renal Replacement Therapy: A Systematic Review of Current Literature

BACKGROUND AND OBJECTIVE

The use of continuous renal replacement therapy (CRRT) for renal support has increased substantially in critically ill children compared with intermittent modalities owing to its preferential effects on hemodynamic stability. With the expanding role of CRRT, the quantification of extracorporeal clearance and the effect on primary pharmacokinetic parameters is of the utmost importance. Within this review, we aimed to summarize the current state of the literature and compare published pharmacokinetic analyses of commonly used medications in children receiving CRRT to those who are not.

METHODS

A systematic search of the literature within electronic databases PubMed, EMBASE, Cochrane Library, and Web of Science was conducted. Published studies that were included contained relevant information on the use of commonly administered medications to children, from neonates to adolescents, receiving CRRT. Pharmacokinetic parameters that were analyzed included volume of distribution, total clearance, extracorporeal clearance, area under the curve, and elimination half-life. Information regarding CRRT circuit, flow rates, and membrane components was analyzed to investigate differences in pharmacokinetics between each modality.

RESULTS

Forty-five studies met the final inclusion criteria within this systematic review, totaling 833 pediatric patients, with 586 receiving CRRT. Antimicrobials were the most common pharmacological class represented within the literature, representing 81% (35/43) of studies analyzed. Children receiving CRRT largely had similar volume of distribution and total clearance to critically ill children not receiving CRRT, suggesting reno-protective dose adjustments may lead to subtherapeutic dosing regimens in these patients. Overall, there was a tendency for hydrophilic agents, with a low protein binding to undergo elevated total clearance in these children. However, results should be interpreted with caution because of the large variability amongst patient populations and heterogeneity with CRRT modalities, flow rates, and use of extracorporeal membrane oxygenation within studies. This review was able to identify that variation in solute removal, or CRRT modalities, properties (i.e., flow rates), and membrane composition, may have differing effects on the pharmacokinetics of commonly administered medications.

CONCLUSIONS

The current state of the literature regarding medications administered to children receiving CRRT largely focuses on antimicrobials. Significant gaps remain with other commonly used medications such as sedatives and analgesics. Overall reporting of patient clinical characteristics, CRRT settings, and circuit composition was poor, with only 10% of articles including all relevant information to assess the impact of CRRT on total clearance. Changes in pharmacokinetics because of CRRT often required higher than labeled doses, suggesting renally adjusted or reno-protective doses may lead to subtherapeutic dosing regimens. A thorough understanding of the interplay between patient, drug, and CRRT-circuit factors are required to ensure adequate delivery of dosing regimens to this vulnerable population.

Contribution of diafiltration and adsorption to vancomycin clearance in a continuous hemodiafiltration circuit model in vitro

BACKGROUND

Vancomycin (VCM) is eliminated mainly by diafiltration under continuous hemodiafiltration (CHDF), but the contribution of adsorption to CHDF clearance (CL_CHDF ) of VCM using a polyacrylonitrile and sodium methallyl sulfonate copolymer membrane coated with polyethylenimine (AN69ST) or a polymethylmethacrylate (PMMA) membrane is unknown. This study sought to investigate the contribution of diafiltration and adsorption to the CL_CHDF of VCM using AN69ST and PMMA membranes in vitro.

METHODS

An in vitro CHDF circuit model was developed. The initial concentration of VCM was 50 μg/mL and human serum albumin (HSA) was prepared at a concentration of 0, 2.5, or 5.0 g/dL. The effluent flow rate (Qe) was set at 800, 1500, or 3000 mL/h. The CL_CHDF , diafiltration rate, and adsorption rate of VCM were calculated.

RESULTS

Total CL_CHDF of VCM using the AN69ST membrane increased and decreased with increasing Qe and HSA concentration, respectively. Diafiltration and adsorption rates were 82.1 ± 9.8% and 12.1 ± 6.1% under all conditions, respectively. Total CL_CHDF using the PMMA membrane increased with increasing Qe. Diafiltration and adsorption rates were 89.2 ± 20.4% and 4.6 ± 17.0% under all conditions, respectively. The observed CL_CHDF values significantly correlated with the predicted CL_CHDF , calculated according to a previous study as the product of Qe and the plasma unbound fraction.

CONCLUSIONS

Diafiltration predominantly contributed to CL_CHDF of VCM using AN69ST and PMMA membranes. When diafiltration rather than adsorption mainly contributes to the CL_CHDF of VCM, the CL_CHDF could be predicted from the Qe and HSA concentration, at least in vitro.

Establishment and application of population pharmacokinetics model of vancomycin in infants with meningitis

BACKGROUND

To establish a population pharmacokinetics (PPK) model of vancomycin (VCM) for dose individualization in Chinese infants with meningitis.

METHODS

We collected the data of 82 children with meningitis in hospital from July 2014 to June 2016. The initial vancomycin dosage regimen for children was 10 or 15 mg/kg for q12 h, q8 h or q6 h. Serum concentrations were determined by Viva-E Analyzer before and after the fifth administration. The PPK model was developed by nonlinear mixed-effect model software, assessed by the bootstrap method and then tested in 20 infant patients.

RESULTS

The VCM clearance (CL) was increased by body weight (WT) and decreased by blood urea nitrogen (BUN). Pharmacokinetic parameters of VCM were not influenced by co-administered drugs. The trough concentrations of VCM were accurately predicted by the PPK model, with the prediction errors less than 32%.

CONCLUSION

A new individual strategy for VCM regimens was proposed and validated by the PPK model.

Antimicrobial Dosing Recommendations in Pediatric Continuous Renal Replacement Therapy: A Critical Appraisal of Current Evidence

OBJECTIVES

Continuous renal replacement therapy (CRRT) is commonly employed in critically ill children and is known to affect antimicrobial pharmacokinetics. There is a lack of readily available, evidence-based antimicrobial dosing recommendations in pediatric CRRT. This study aims to quantify commonly used antimicrobial drugs in pediatric CRRT and identify gaps between contemporary literature-based dosing recommendations and those presented in a frequently used dosing reference.

METHODS

The Pediatric Health Information System (PHIS) database was queried from July 1, 2018 through June 30, 2021 to identify admissions in which antimicrobials were billed on the same day as CRRT. Drugs of interest were selected if at least 10% of admission involved administration on at least one CRRT day, with additional clinically important antimicrobials selected by the authors. A comprehensive literature search was performed to identify antimicrobial pharmacokinetic (PK) studies in children for each selected drug. For identified articles, dosing recommendations were extracted and compared to those in a popular tertiary dosing reference (Lexi-Comp Online database). The level of agreement of the dosing recommendations was assessed.

RESULTS

77 unique antimicrobial agents were identified amongst 812 admissions from 20 different PHIS hospitals. Fifteen antimicrobials were billed on the same day as CRRT in ≥10% of admissions, with 4 additional drugs deemed clinically relevant by the authors. Twenty PK studies were identified for these 19 drugs, and dosing recommendations were included in 8 (42.1%) of them. Seventeen agents (89.5%) had some type of CRRT-specific dosing guidance in Lexi-Comp, with only 1 directly based on a pediatric CRRT study. For the 8 agents with PK data available, Lexi-Comp recommendations matched primary literature dosing guidance in 3 (37.5%). Two (25%) lacked agreement between the Lexi-Comp and primary literature, and the remaining 3 (37.5%) had partial agreement with multiple dosing regimens suggested in the primary literature and at least one of these regimens recommended by Lexi-Comp.

CONCLUSION

Significant gaps exist in the data supporting antimicrobial dosing recommendations for children receiving CRRT. Future studies should focus on antimicrobial dosing in pediatric CRRT, emphasizing provision of robust data from which dosing recommendations can be promptly incorporated into tertiary dosing references.

Patient-centered outcomes in pediatric continuous kidney replacement therapy: new morbidity and worsened functional status in survivors

BACKGROUND

Ongoing measures to improve pediatric continuous kidney replacement therapy (CKRT) have lowered mortality rates, shifting the focus to survivor functional status. While septic acute kidney injury generates new morbidity in pediatric critically ill patients, acquired morbidities and functional status of CKRT population are unknown. We predicted that CKRT survivors are at risk for new morbidity and would have worse functional status at PICU discharge compared to baseline, and aimed to describe associated factors.

METHODS

Retrospective cohort study over 24 months of CKRT patients surviving to PICU discharge in a quaternary children's hospital. Functional outcome was determined by Functional Status Scale (FSS).

RESULTS

FSS scores were higher at PICU and hospital discharge compared to baseline. Of 45 CKRT survivors, 31 (69%) had worse FSS score at PICU discharge and 51% had new morbidity (≥3 increase in FSS); majority qualified as moderate to severe disability (FSS ≥10). Four patients (9%) had new tracheostomy, 3 (7%) were ventilator dependent, and 10 (22%) were dialysis dependent. Most (23/45, 51%) required outpatient rehabilitation. Cumulative days on sedation, controlled for illness severity, were independently associated with worse FSS at PICU discharge (aOR 25.18 (3.73, 169.92)). In adjusted analyses, duration of sedation was associated with new morbidity, while neurologic comorbidity, percent fluid overload at CKRT start, and nonrenal comorbidity were associated with moderate to severe disability at PICU discharge when controlled for baseline FSS.

CONCLUSIONS

CKRT survivors, with new morbidity and worse functional outcomes at PICU discharge, are a newly described vulnerable population requiring targeted follow-up. Deliberate decrease of sedation exposure in patients with decreased clearance due to organ dysfunction needs to be studied as a modifiable risk factor.

Dose Tailoring of Vancomycin Through Population Pharmacokinetic Modeling Among Surgical Patients in Pakistan

Background: Vancomycin is a narrow therapeutic agent, and it is necessary to optimize the dose to achieve safe therapeutic outcomes. The purpose of this study was to identify the significant covariates for vancomycin clearance and to optimize the dose among surgical patients in Pakistan. Methods: Plasma concentration data of 176 samples collected from 58 surgical patients treated with vancomycin were used in this study. A population pharmacokinetic model was developed on NONMEM^® using plasma concentration-time data. The effect of all available covariates was evaluated on the pharmacokinetic parameters of vancomycin by stepwise covariate modeling. The final model was evaluated using bootstrap, goodness-of-fit plots, and visual predictive checks. Results: The pharmacokinetics of vancomycin followed a one-compartment model with first-order elimination. The vancomycin clearance (CL) and volume of distribution (Vd) were 2.45 L/h and 22.6 l, respectively. Vancomycin CL was influenced by creatinine clearance (CRCL) and body weight of the patients; however, no covariate was significant for its effect on the volume of distribution. Dose tailoring was performed by simulating dosage regimens at a steady state based on the CRCL of the patients. The tailored doses were 400, 600, 800, and 1,000 mg for patients with a CRCL of 20, 60, 100, and 140 ml/min, respectively. Conclusion: Vancomycin CL is influenced by CRCL and body weight of the patient. This model can be helpful for the dose tailoring of vancomycin based on renal status in Pakistani patients.

An Update on Population Pharmacokinetic Analyses of Vancomycin, Part II: In Pediatric Patients

Vancomycin is widely used in pediatric patients, however, large inter- and intraindividual variability are observed in vancomycin pharmacokinetics, affecting proper therapeutic monitoring. This review aimed at providing a comprehensive synthesis of the population pharmacokinetic models of vancomycin in pediatric patients and identifying potential factors responsible for the variability observed in various subpopulations. We conducted a literature search of the PubMed and EMBASE databases to obtain population pharmacokinetic studies for vancomycin published between January 2011 and January 2020, which resulted in a total of 33 studies. Vancomycin pharmacokinetics were generally characterized using a one-compartment model (n = 27), while a two-compartment model was used in six studies. The median (interquartile range) of the typical vancomycin clearance (CL) and the total volume of distribution adjusted to the median or mean body weight of the respective study was 0.103 L/h/kg (0.071-0.125) and 0.64 L/kg (0.59-1.03), respectively. Median weight-adjusted CL between different child age groups, such as infants and adolescents, did not appear to vary significantly, although the sample size for many age groups was very small. Examples of the conditions with relatively abnormal vancomycin pharmacokinetic values include renal insufficiency, sepsis, hematological and solid malignancy, and hypothermia treatment. Factors influencing pediatric vancomycin pharmacokinetics after adjusting for size and maturation include various renal function descriptors and some case-specific variables such as dialysate flow rate, ultrafiltrate output, and hypothermia. This review was able to document possible variables explaining the high variability observed in certain subpopulations and contrast vancomycin pharmacokinetics in different pediatric subpopulations.

Pharmacokinetics of Antibiotics in Pediatric Intensive Care: Fostering Variability to Attain Precision Medicine

Children show important developmental and maturational changes, which may contribute greatly to pharmacokinetic (PK) variability observed in pediatric patients. These PK alterations are further enhanced by disease-related, non-maturational factors. Specific to the intensive care setting, such factors include critical illness, inflammatory status, augmented renal clearance (ARC), as well as therapeutic interventions (e.g., extracorporeal organ support systems or whole-body hypothermia [WBH]). This narrative review illustrates the relevance of both maturational and non-maturational changes in absorption, distribution, metabolism, and excretion (ADME) applied to antibiotics. It hereby provides a focused assessment of the available literature on the impact of critical illness—in general, and in specific subpopulations (ARC, extracorporeal organ support systems, WBH)—on PK and potential underexposure in children and neonates. Overall, literature discussing antibiotic PK alterations in pediatric intensive care is scarce. Most studies describe antibiotics commonly monitored in clinical practice such as vancomycin and aminoglycosides. Because of the large PK variability, therapeutic drug monitoring, further extended to other antibiotics, and integration of model-informed precision dosing in clinical practice are suggested to optimise antibiotic dose and exposure in each newborn, infant, or child during intensive care.

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.

Personalized Dosing of Intravenous Vancomycin Among Critically Ill Neonates in Hong Kong: Harnessing Electronic Health Records to Develop a Web-Based Dosing Interface (Preprint)

Background

Intravenous (IV) vancomycin is used in the treatment of severe infection in neonates. However, its efficacy is compromised by elevated risks of acute kidney injury. The risk is even higher among neonates admitted to the neonatal intensive care unit (NICU), in whom the pharmacokinetics of vancomycin vary widely. Therapeutic drug monitoring is an integral part of vancomycin treatment to balance efficacy against toxicity. It involves individual dose adjustments based on the observed serum vancomycin concentration (VC_s). However, the existing trough-based approach shows poor evidence for clinical benefits. The updated clinical practice guideline recommends population pharmacokinetic (popPK) model–based approaches, targeting area under curve, preferably through the Bayesian approach. Since Bayesian methods cannot be performed manually and require specialized computer programs, there is a need to provide clinicians with a user-friendly interface to facilitate accurate personalized dosing recommendations for vancomycin in critically ill neonates.

Objective

We used medical data from electronic health records (EHRs) to develop a popPK model and subsequently build a web-based interface to perform model-based individual dose optimization of IV vancomycin for NICU patients in local medical institutions.

Methods

Medical data of subjects prescribed IV vancomycin in the NICUs of Prince of Wales Hospital and Queen Elizabeth Hospital in Hong Kong were extracted from EHRs, namely the Clinical Information System, In-Patient Medication Order Entry, and electronic Patient Record. Patient demographics, such as body weight and postmenstrual age (PMA), serum creatinine (SCr), vancomycin administration records, and VC_s were collected. The popPK model employed a 2-compartment infusion model. Various covariate models were tested against body weight, PMA, and SCr, and were evaluated for the best goodness of fit. A previously published web-based dosing interface was adapted to develop the interface in this study.

Results

The final data set included EHR data extracted from 207 subjects, with a total of 689 VC_s measurements. The final model chosen explained 82% of the variability in vancomycin clearance. All parameter estimates were within the bootstrapping CIs. Predictive plots, residual plots, and visual predictive checks demonstrated good model predictability. Model approximations showed that the model-based Bayesian approach consistently promoted a probability of target attainment (PTA) above 75% for all subjects, while only half of the subjects could achieve a PTA over 50% with the trough-based approach. The dosing interface was developed with the capability to optimize individual doses with the model-based empirical or Bayesian approach.

Conclusions

Using EHRs, a satisfactory popPK model was verified and adopted to develop a web-based individual dose optimization interface. The interface is expected to improve treatment outcomes of IV vancomycin for severe infections among critically ill neonates. This study provides the foundation for a cohort study to demonstrate the utility of the new approach compared with previous dosing methods.

Effective treatment of vancomycin nephrotoxicity with continuous venous-venous haemodiafiltration (CVVHDF) in a paediatric patient

WHAT IS KNOWN AND OBJECTIVE

Vancomycin removal by dialysis uses methods that differ in type of dialysis membrane, dialysis fluxes and duration, ultrafiltration rate and Kt/V_urea (K = dialyser urea clearance, t = time on dialysis and V = total body water) in case of nephrotoxicity. We applied continuous venous-venous haemodiafiltration (CVVHDF) to treat a paediatric case of vancomycin nephrotoxicity caused by high serum trough concentrations.

CASE SUMMARY

We report the case of a 4-year and 7-month-old boy with serum trough concentration of vancomycin of 86.0 mg/L after a 2-day treatment with vancomycin. His serum creatinine increased from 13.3 μmol/L at baseline to 227.0 μmol/L. We discontinued vancomycin and performed a 22-hours CVVHDF with high-flux membrane. Vancomycin decreased by 69.4% (82.1-25.1 mg/L), and renal function improved.

WHAT IS NEW AND CONCLUSION

Therapeutic drug monitoring and laboratory indicator measurements should be performed early during vancomycin treatment in paediatric patients with nephrotoxicity risk factors. Vancomycin removal by CVVHDF can be effective in paediatric acute kidney injury (AKI) associated with vancomycin-associated nephrotoxicity (VAN).