Influences of renal function descriptors on population pharmacokinetic modeling of vancomycin in Chinese adult patients

Evaluation of Vancomycin Dose Needed to Achieve 24-Hour Area Under the Concentration-Time Curve to Minimum Inhibitory Concentration Ratio Greater Than or Equal to 400 Using Pharmacometric Approaches in Pediatric Intensive Care Patients

OBJECTIVES

To investigate which independent factor(s) have an impact on the pharmacokinetics of vancomycin in critically ill children, develop an equation to predict the 24-hour area under the concentration-time curve from a trough concentration, and evaluate dosing regimens likely to achieve a 24-hour area under the concentration-time curve to minimum inhibitory concentration ratio (AUC24/MIC) greater than or equal to 400.

DESIGN

Prospective population pharmacokinetic study of vancomycin.

SETTING

Critically ill patients in quaternary care PICUs.

PATIENTS

Children 90 days old or older to younger than 18 years who received IV vancomycin treatment, irrespective of the indication for use, in the ICUs at the University of Maryland Children's Hospital and Texas Children's Hospital were enrolled.

INTERVENTIONS

Vancomycin was prescribed at doses and intervals chosen by the treating clinicians.

MEASUREMENTS AND MAIN RESULTS

A median of four serum levels of vancomycin per patient were collected along with other variables for up to 7 days following the first administration. These data were used to characterize vancomycin pharmacokinetics and evaluate the factors affecting the variability in achieving AUC24/MIC ratio greater than or equal to 400 in PICU patients who are not on extracorporeal therapy. A total of 302 children with a median age of 6.0 years were enrolled. A two-compartment model described the pharmacokinetics of vancomycin with the clearance of 2.76 L/hr for a typical patient weighing 20 kg. The glomerular filtration rate estimated using either the bedside Schwartz equation or the chronic kidney disease in children equation was the only statistically significant predictor of clearance among the variables evaluated, exhibiting equal predictive performance. The trough levels achieving AUC24/MIC = 400 were 5.6-10.0 μg/mL when MIC = 1 μg/mL. The target of AUC24/MIC greater than or equal to 400 was achieved in 60.4% and 36.5% with the typical dosing regimens of 15 mg/kg every 6 and 8 hours (q6h and q8h), respectively.

CONCLUSIONS

The pharmacokinetics of vancomycin in critically ill children were dependent on the estimated glomerular filtration rate only. Trough concentrations accurately predict AUC24. Typical pediatric vancomycin dosing regimens of 15 mg/kg q6h and q8h will often lead to AUC24/MIC under 400.

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.

Selecting the Best Pharmacokinetic Models for a Priori Model-Informed Precision Dosing with Model Ensembling

BACKGROUND AND OBJECTIVE

When utilizing population pharmacokinetic (popPK) models for a priori dosage individualization, selecting the best model is crucial to obtain adequate doses. We developed and evaluated several model-selection and ensembling methods, using external evaluation on the basis of therapeutic drug monitoring (TDM) samples to identify the best (set of) models per patient for a priori dosage individualization.

METHODS

PK data and models describing both hospitalized patients (n = 134) receiving continuous vancomycin (26 models) and patients (n = 92) receiving imatinib in an outpatient setting (12 models) are included. Target attainment of four model-selection methods was compared with standard dosing: the best model based on external validation, uninformed model ensembling, model ensembling using a weighting scheme on the basis of covariate-stratified external evaluation, and model selection using covariates in decision trees that were subsequently ensembled.

RESULTS

Overall, the use of PK models improved the proportion of patients exposed to concentrations within the therapeutic window for both cohorts. Relative improvement of proportion on target for best model, unweighted, weighted, and decision trees were - 7.0%, 2.3%, 11.4%, and 37.0% (vancomycin method-development); 23.2%, 7.9%, 15.6%, and, 77.2% (vancomycin validation); 40.7%, 50.0%, 59.5%, and 59.5% (imatinib method-development); and 19.0%, 28.5%, 38.0%, and 23.8% (imatinib validation), respectively.

CONCLUSIONS

The best (set of) models per patient for a priori dosage individualization can be identified using a relatively small set of TDM samples as external evaluation. Adequately performing popPK models were identified while also excluding poor-performing models. Dose recommendations resulted in more patients within the therapeutic range for both vancomycin and imatinib. Prospective validation is necessary before clinical implementation.

Age-Related Differences in Vancomycin-Associated Nephrotoxicity and Efficacy in Methicillin-Resistant Staphylococcus aureus Infection: A Comparative Study between Elderly and Adult Patients

Elderly patients (age ≥ 65 years) are susceptible to methicillin-resistant Staphylococcus aureus (MRSA) infections, with potential for more adverse treatment outcomes or complications compared to younger adults (18-64 years). This study compared vancomycin-associated nephrotoxicity and efficacy in elderly and adult patients and investigated the correlation between vancomycin pharmacokinetic/pharmacodynamic (PK/PD) indices and clinical outcomes. A prospective study was conducted in 10 hospitals in Shanghai from October 2012 to November 2019. A total of 164 patients with MRSA infections were enrolled, including 83 elderly and 81 adult patients. Vancomycin therapeutic drug monitoring (TDM) was performed in all patients, indicating significantly higher vancomycin trough concentrations (Ctrough), 24-h area under the curve (AUC24) values, and AUC24/minimum inhibitory concentration (AUC24/MIC) values in elderly patients compared to adult patients. The incidence of vancomycin-associated nephrotoxicity was nearly three times higher in elderly patients (18.1% vs. 6.2%, p = 0.020), despite similar clinical and microbiological efficacy. Of particular importance, a Ctrough > 20 mg/L was found as an independent factor of nephrotoxicity in elderly patients. Further analysis of patients with an estimated glomerular filtration rate (eGFR) > 60 mL/min/1.73 m2 also revealed that elderly patients had significantly higher vancomycin-related PK/PD indices and more nephrotoxicity than adult patients. In conclusion, elderly patients receiving vancomycin therapy face a higher risk of nephrotoxicity, which requires close vancomycin TDM, especially when the Ctrough exceeds 20 mg/L.

Population pharmacokinetics of antibacterial agents in the older population: a literature review

INTRODUCTION

Older individuals face an elevated risk of developing bacterial infections. The optimal use of antibacterial agents in this population is challenging because of age-related physiological alterations, changes in pharmacokinetics (PK) and pharmacodynamics (PD), and the presence of multiple underlying diseases. Therefore, population pharmacokinetics (PPK) studies are of great importance for optimizing individual treatments and prompt identification of potential risk factors.

AREA COVERED

Our search involved keywords such as 'elderly,' 'old people,' and 'geriatric,' combined with 'population pharmacokinetics' and 'antibacterial agents.' This comprehensive search yielded 11 categories encompassing 28 antibacterial drugs, including vancomycin, ceftriaxone, meropenem, and linezolid. Out of 127 studies identified, 26 (20.5%) were associated with vancomycin, 14 (11%) with meropenem, and 14 (11%) with piperacillin. Other antibacterial agents were administered less frequently.

EXPERT OPINION

PPK studies are invaluable for elucidating the characteristics and relevant factors affecting the PK of antibacterial agents in the older population. Further research is warranted to develop and validate PPK models for antibacterial agents in this vulnerable population.

Reconsideration of the current models of estimated kidney function-based drug dose adjustment in older adults: The role of biological age

Human lifespan has increased from a median of 46.5 years in 1950 to 71.7 years in 2022. As people age, one of the inevitable consequences is a decline in kidney function and glomerular filtration rate (GFR) which can have direct or indirect effects on the pharmacokinetic and pharmacodynamic profiles of many drugs. Numerous equations have been developed to generate estimated GFR (eGFR) using the two principal biomarkers: serum creatinine and serum cystatin C. However, the trajectory of changes with aging is dissimilar in these equations. In addition, there is recognition that chronological age (lifespan) often does not reflect biological age (healthspan) as an essential parameter in kidney function equations. In the past decade, there has been an increasing interest in quantifying biological age and new commercially available assays have entered the marketplace. In this narrative review, we illustrate how dominant equations of eGFR model the fractional change in this parameter very differently across chronological age. In addition, we review various biological age indicators (aging clocks) and challenges to their application in clinical practice. Importantly, by comparing vancomycin's mean clearance as a drug with limited metabolism and unchanged elimination between two age milestones in some recent population pharmacokinetic models, we show how efforts to quantify kidney function in older adults optimally remain under-explored, particularly those at the upper end of their lifespan. We also propose considering new models that integrate biological age as a new pathway to improve precision drug dosing in older adults.

Individualized Delivery of Vancomycin by Model-Informed Bayesian Dosing Approach to Maintain an AUC24 Target in Critically Ill Patients

INTRODUCTION

Monitoring of AUC24 was updated recommendation in the guideline for the therapeutic drug monitoring (TDM) of vancomycin in Chinese pharmacological society published in 2020. Vancomycin pharmacokinetic profiles are diverse and unique in critically ill patients because of the drastic variability of the patients' physiological parameters, while the study for population pharmacokinetic (PPK) models in Chinese critically ill patients has been rarely reported. The objectives of this study were to construct a PPK model to describe the pharmacokinetic characteristics of vancomycin in critically ill patients and to individualize vancomycin dosing by model-informed Bayesian estimation for maintenance of AUC24 target at 400-650 mg h/L recommended by the 2020 guideline.

METHODS

Vancomycin with different dosing was administered intravenously over 1 h for critically ill patients, TDM was started at 48 h or 72 h since initiation of vancomycin therapy for patients. Blood samples were collected from patients for trough concentrations or Cmax. Vancomycin concentrations were determined by high-performance liquid chromatography method with ultraviolet detection. PPK model was performed using the nonlinear mixed-effect model (NONMEM®). Individual PK parameters for critically ill patients treated with vancomycin were estimated using a post hoc empirical Bayesian method based on the final PPK model. AUC24 was calculated as the total daily dose divided by the clearance (L/h).

RESULTS

The PPK of vancomycin was determined by a one-compartment model with creatinine clearance as fixed effects. The PK estimates in the final model generally agreed with the median estimates and were contained within the 95% CI generated from the bootstrap results, indicating good precision and stability in the final model. The visual predictive check plots showed the adequate predictive performance of the final PK model and supported a good model fit. The model-informed Bayesian estimation was used to predict the AUC24 of critically ill patient by the acquired TDM results, and the dosing adjustment by maintenance of AUC24 at 400-650 mg h/L had made a great therapeutic effect for the case.

CONCLUSION

This study established a PPK model of vancomycin in Chinese critically ill patients, and individualized dosing of vancomycin by model-informed Bayesian estimation to maintain an AUC24 target at 400-650 mg h/L has been successfully applied in clinic. This result supports the continued use of model-informed Bayesian estimation to vancomycin treatment in critically ill patients.

Two Innovative Approaches to Optimize Vancomycin Dosing Using Estimated AUC after First Dose: Validation Using Data Generated from Population PK Model Coupled with Monte-Carlo Simulation and Comparison with the First-Order PK Equation Approach

The revised consensus guidelines for optimizing vancomycin doses suggest that maintaining the area under the concentration-time curve to minimal inhibitory concentration ratio (AUC/MIC) of 400–600 mg·h/L is the target pharmacokinetic/pharmacodynamic (PK/PD) index for efficacy. AUC-guided dosing approach uses a first-order pharmacokinetics (PK) equation to estimate AUC using two samples obtained at steady state and one-compartment model, which can cause inaccurate AUC estimation and fail to achieve the effective PK/PD target early in therapy (days 1 and 2). To achieve an efficacy target from the third or fourth dose, two innovative approaches (Method 1 and Method 2) to estimate vancomycin AUC at steady state (AUCSS) using two-compartment model and three or four levels after the first dose are proposed. The feasibility of the proposed methods was evaluated and compared with another published dosing algorithm (Method 3), which uses two samples and a one-compartment approach. Monte Carlo simulation was performed using a well-established population PK model, and concentration-time profiles for virtual patients with various degrees of renal function were generated, with 1000 subjects per group. AUC extrapolated to infinity (AUC0–∞) after the first dose was estimated using the three methods, whereas reference AUC (AUCref) was calculated using the linear-trapezoidal method at steady state after repeated doses. The ratio of AUC0–∞: AUCref and % bias were selected as the indicators to evaluate the accuracy of three methods. Sensitivity analysis was performed to examine the influence of change in each sampling time on the estimated AUC0–∞ using the two proposed approaches. For simulated patients with various creatinine clearance, the mean of AUC0–∞: AUCref obtained from Method 1, Method 2 and Method 3 ranged between 0.98 to 1, 0.96 to 0.99, and 0.44 to 0.69, respectively. The mean bias observed with the three methods was −0.10% to −2.09%, −1.30% to −3.59% and −30.75% to −55.53%, respectively. The largest mean bias observed by changing sampling time while using Method 1 and Method 2 were −4.30% and −10.50%, respectively. Three user-friendly and easy-to-use excel calculators were built based on the two proposed methods. The results showed that our approaches ensured sufficient accuracy and achieved target PK/PD index early and were superior to the published methodologies. Our methodology has the potential to be used for vancomycin dose optimization and can be easily implemented in clinical practice.

Model-informed precision dosing of vancomycin via continuous infusion: a clinical fit-for-purpose evaluation of published PK models

BACKGROUND

Model-informed precision dosing (MIPD) is an innovative approach used to guide bedside vancomycin dosing. The use of Bayesian software requires suitable and externally validated population pharmacokinetic (popPK) models.

OBJECTIVES

Therefore, we aimed to identify suitable popPK models for a priori prediction and a posteriori forecasting of vancomycin in continuous infusion. Additionally, a model averaging (MAA) and a model selection approach (MSA) were compared with the identified popPK models.

METHODS

. Clinical PK data were retrospectively collected from patients receiving continuous vancomycin therapy and admitted to a general ward of three large Belgian hospitals. The predictive performance of the popPK models, identified in a systematic literature search, as well as the MAA/MSA was evaluated for the a priori and a posteriori scenarios using bias, root mean square errors, normalized prediction distribution errors and visual predictive checks.

RESULTS

The predictive performance of 23 popPK models was evaluated based on clinical data from 169 patients and 923 therapeutic drug monitoring samples. Overall, the best predictive performance was found using the Okada model (bias < -0.1 mg/L), followed by the Colin model. The MAA/MSA predicted with a constantly high precision and low inaccuracy and were clinically acceptable in the Bayesian forecasting.

CONCLUSION

This study identified the two-compartmental models of Okada et al. and Colin et al. as most suitable for non-ICU patients to forecast individual exposure profiles after continuous vancomycin infusion. The MAA/MSA performed equally good as the individual popPK models. Both approaches could therefore be used in clinical practice to guide dosing decisions.

Population pharmacokinetic modeling and clinical application of vancomycin in Chinese patients hospitalized in intensive care units

Management of vancomycin administration for intensive care units (ICU) patients remains a challenge. The aim of this study was to describe a population pharmacokinetic model of vancomycin for optimizing the dose regimen for ICU patients. We prospectively enrolled 466 vancomycin-treated patients hospitalized in the ICU, collected trough or approach peak blood samples of vancomycin and recorded corresponding clinical information from July 2015 to December 2017 at Tai Zhou Hospital of Zhejiang Province. The pharmacokinetics of vancomycin was analyzed by nonlinear mixed effects modeling with Kinetica software. Internal and external validation was evaluated by the maximum likelihood method. Then, the individual dosing regimens of the 92 patients hospitalized in the ICU whose steady state trough concentrations exceeded the target range (10–20 μg/ml) were adjusted by the Bayes feedback method. The final population pharmacokinetic model show that clearance rate (CL) of vancomycin will be raised under the conditions of dopamine combined treatment, severe burn status (Burn-S) and increased total body weight (TBW), but reduced under the conditions of increased serum creatinine (Cr) and continuous renal replacement therapy status; Meanwhile, the apparent distribution volume (V) of vancomycin will be enhanced under the terms of increased TBW, however decreased under the terms of increased age and Cr. The population pharmacokinetic parameters (CL and V) according to the final model were 3.16 (95%CI 2.83, 3.40) L/h and 60.71 (95%CI 53.15, 67.46). The mean absolute prediction error for external validation by the final model was 12.61% (95CI 8.77%, 16.45%). Finally, the prediction accuracy of 90.21% of the patients’ detected trough concentrations that were distributed in the target range of 10–20 μg/ml after dosing adjustment was found to be adequate. There is significant heterogeneity in the CL and V of vancomycin in ICU patients. The constructed model is sufficiently precise for the Bayesian dose prediction of vancomycin concentrations for the population of ICU Chinese patients.

Physiologically based pharmacokinetic model of renally cleared antibacterial drugs in Chinese renal impairment patients

To preliminarily develop physiologically based population models for Chinese renal impairment patients and to evaluate the prediction performance of new population models by renally cleared antibacterial drugs. First, demographic data and physiological parameters of Chinese renal impairment patients were collected, and then the coefficients of the relative demographic and physiological equation were recalibrated to construct the new population models. Second, drug‐independent parameters of ceftazidime, cefodizime, vancomycin, and cefuroxime were collected and verified by Chinese healthy volunteers, Caucasian healthy volunteers, and Caucasian renal impairment population models built in Simcyp. Finally, the newly developed population models were applied to predict the plasma concentration of four antibacterial drugs in Chinese renal impairment patients. The new physiologically based pharmacokinetic (PBPK) population models can predict the main pharmacokinetic parameters, including area under the plasma concentration–time curve extrapolated to infinity (AUC_inf), renal clearance (CL_r), and peak concentration (C_max), of ceftazidime, cefodizime, vancomycin, and cefuroxime following intravenous administrations with less than twofold error in mild, moderate, and severe Chinese renal impairment patients. The accuracy and precision of the predictions were improved compared with the Chinese healthy volunteers and Caucasian renal impairment population models. The PBPK population models were preliminarily developed and the first‐step validation results of four antibacterial drugs following intravenous administration showed acceptable accuracy and precision. The population models still need more systematic validation by using more drugs and scenarios in future studies to support their applications on dosage recommendation for Chinese renal impairment patients.

Population Pharmacokinetics of Vancomycin in Kidney Transplant Recipients: Model Building and Parameter Optimization

Background

Depending on the renal function of patients and many other influencing factors, studies on vancomycin pharmacokinetics show significant inter- and intra-individual variability. The present study was conducted using a population pharmacokinetics method to investigate the pharmacokinetic parameters and identified their influencing covariates for intravenous vancomycin in adult kidney transplant recipients.

Methods

The drug monitoring data included 56 adult renal transplant recipients who received intravenous vancomycin as prophylactic medication. The analysis was performed by a population approach with NONMEM. Data were collected mainly during the first week after transplantation. Monitoring of vancomycin trough concentration in blood was initiated mainly 3–5 days after the initial administration.

Results

The one-compartment open model was optimal and adequately described the data. Body weight (WT) and estimated glomerular filtration rate (GFR) were identified as significant covariates of the pharmacokinetic parameters CL and V of intravenous vancomycin in the kidney transplant patients. The typical values of vancomycin CL and V were 2.08 L h^-1 and 63.2 L, respectively. A dosage strategy scheme according to model results was also designed.

Conclusion

Both WT and GFR of the kidney transplant patients positively influence the pharmacokinetic parameters CL and V for intravenous vancomycin. Our population pharmacokinetic model provides a reference for vancomycin dosage adjustment in kidney transplant recipients.

Ardakani Y, Rajabi M, Namazi S. Evaluation of the Association between Trough and Area Under the Curve to Minimum Inhibitory Concentration Ratio (AUC24/MIC) of Vancomycin in Infected Patients with Methicillin Resistant Staphylococcus aureus (MRSA)

Background: The recent studies emphasized on the correlation of vancomycin antibacterial effect with pharmacokinetics properties such as the area under the curve/minimum inhibitory concentration (AUC24/MIC) ≥400 and serum trough level 15-20 mg /L in the patients with severe infection with methicillin-resistant Staphylococcus aureus (MRSA). The purpose is to assay the vancomycin pharmacokinetic properties in our population and evaluates the correlation between AUC24/MIC and trough serum level of vancomycin in given patients. Methods: The patients with a positive MRSA culture, treated with vancomycin, were enrolled in this cross-sectional study. Three plasma samples were obtained during the study including 30 min before fourth and the fifth dose as trough levels and 1 hour after the fourth dose as peak level to determine AUC24. E-TEST determined the MIC of vancomycin. Results: Thirty-eight patients with an average age of 48.33±16.44 were enrolled in this study. The mean ± SD of MIC was 0.99±0.30 mg/L. Thirty-four patients reached the adequate therapeutic range of AUC24/MIC ≥ 400 due to the standard vancomycin dosing method. In comparison, only 7 and 10 patients had the first and second trough levels in target intervals of 15-20 mg/L, respectively. Due to the receiver operating characteristic curve test (ROC test), the trough level after the fourth dose had a strong correlation with target AUC24/MIC with a sensitivity of 94.1%and specificity of 75.0%. Conclusion: This study concluded using only a trough level is not appropriate for therapeutic drug monitoring (TDM) of vancomycin. In our population, target AUC24/MIC (≥ 400) had a reasonably strong correlation with the trough level before the fifth dose which achieved with trough level ≥10.81 mg/L and MIC< 1 mg/L.

Comparison of the Predictive Performance Between Cystatin C and Serum Creatinine by Vancomycin via a Population Pharmacokinetic Models: A Prospective Study in a Chinese Population

BACKGROUND

Most of the current published population pharmacokinetic (PopPK) models are based on serum creatinine, but we often encounter an underestimation of its concentration in our clinical work. Therefore, we established a cystatin C-based model of vancomycin.

OBJECTIVES

The purpose of this study was to externally verify the PopPK model of vancomycin based on the glomerular filtration rate (GFR) estimated by serum cystatin C in our previous study and to compare the prediction performance of cystatin C (Cys C) and serum creatinine (SCR)-based models.

METHODS

The external data set consists of adults receiving vancomycin treatment at The First Affiliated Hospital of Guangxi Medical University. We summarized and restored published models based on serum creatinine values from the literature and used our external data set for initial screening. Visual and external verifications were used to further select candidate models for comparison. The mean prediction error (ME), mean absolute error (MAE) and root mean squared error (RMSE) were the primary outcomes for the overall comparison. Group comparisons of patients with different glomerular filtration rates (GFRs), ages and body mass index (BMI) levels were obtained by the Bayesian method.

RESULTS

A total of 156 patients with 233 samples were collected as an external data set. Sixteen published models were summarized and restored. After screening, four candidate models suitable for the external data set were finally obtained for comparison. The cystatin C-based model has a smaller ME value in the overall comparison. In the group comparison, serum creatinine-based models were underestimated in the prediction for patient groups with age ≥ 60 years, abnormal BMI values and GFR < 90 ml/min/1.73 m², for which the cystatin C-based model could solve this problem.

CONCLUSION

After comparison, we suggest that cystatin C is a superior renal function marker to serum creatinine for vancomycin PopPK models.

Simultaneous separation and determination of vancomycin and its crystalline degradation products in human serum by ultra high performance liquid chromatography tandem mass spectrometry method and its application in therapeutic drug monitoring

A rapid and simple ultra high performance liquid chromatography with tandem mass spectrometry method was developed and validated for the simultaneous separation and determination of vancomycin and its crystalline degradation products in human serum. Vancomycin and two isomers of the degradants were extracted from human serum with a protein precipitation method. The compounds were separated on an Acquity BEH C18 column (2.1 × 50 mm, 1.7 μm) eluted with a gradient mixture of acetonitrile and 0.1% formic acid as the mobile phase. Norvancomycin was used as the internal standard. The linear ranges of vancomycin and two degradant isomers were 1.057-105.7, 0.1437-14.37, and 0.2540-25.40 μg/mL, respectively. The established methods were validated and successfully applied to a therapeutic drug monitoring study of vancomycin in patients with renal insufficiency.

The potential risk factors of nephrotoxicity during vancomycin therapy in Chinese adult patients

OBJECTIVE

To evaluate potential risk factors that may make patients susceptible to nephrotoxicity in those concomitantly receiving vancomycin in the hospital.

METHODS

This was a single-centre retrospective analysis of patients treated with vancomycin for gram-positive or mixed infections in the Renmin Hospital of Wuhan University from January 2017 to May 2018. All of them were treated for ≥48 hours and had no kidney disease. Nephrotoxicity refers to acute kidney diseases and disorders after the use of vancomycin, and includes acute kidney injury. Univariate analysis and binary logistic regression analysis with the forward stepwise method were used to assess the risk factors associated with nephrotoxicity.

RESULTS

Of the 790 patients treated with vancomycin, only 257 patients met the inclusion criteria, and 40 (15.6%) subjects developed nephrotoxicity. Significant differences (p<0.05) were seen in the number of combined antimicrobials (p=0.012), dose adjustment (p<0.001), more than three antimicrobials (p=0.015), monitoring trough concentrations (p=0.001), furosemide (p<0.001), torasemide (p<0.001), cefoperazone sodium tazobactam sodium (p=0.039), voriconazole (p=0.012) and ganciclovir (p=0.008). Regression analysis further indicated that furosemide (OR 7.983, p<0.001) and torasemide (OR 3.496, p<0.001) were risk factors for vancomycin nephrotoxicity. Diabetes mellitus (OR 3.062, p=0.035), voriconazole (OR 3.515, p=0.020) and fluconazole (OR 3.326, p=0.018) might be also risk factors.

CONCLUSION

Fluconazole and voriconazole might be potential risk factors for vancomycin nephrotoxicity, besides furosemide and torasemide. It is not recommended to use imipenem cilastatin sodium and vancomycin at the same time. If necessary, meropenem may be safer. Appropriate combination drugs, cautious initial dose or timely dose adjustment might reduce the occurrence of nephrotoxicity when using vancomycin.

The effect of body mass index and creatinine clearance on serum trough concentration of vancomycin in adult patients

Background

The aim of this study was to evaluate the influence of patient body mass index (BMI) and estimated creatinine clearance (CrCl) on serum vancomycin concentrations to define a possible optimal dosage regimen in overweight patients based on data obtained during therapeutic drug monitoring.

Methods

This retrospective study used data collected from January 2017 to January 2019. Adult patients (n = 204) received vancomycin treatment at a dose of 1000 mg every 12 h and underwent serum monitoring. Data collected included patient disease category, sex, age, height, weight, vancomycin concentrations, and serum creatinine. The CrCl values were estimated using the Cockcroft-Gault formula. In this study, statistical comparisons were performed on the results of patients according to serum vancomycin concentration.

Results

Serum vancomycin concentration was significantly related to BMI (P <  0.001) and CrCl (P <  0.05) in adult patients. Furthermore, the trough serum vancomycin concentration showed a logarithmic correlation with BMI (R = − 0.5108, 95% CI: − 0.6082 to − 0.3982, P <  0.001) and CrCl (R = − 0.5739, 95% CI: − 0.6616 to − 0.4707, P <  0.001). The multivariate analysis showed that BMI and CrCl are independent contributors to the trough vancomycin concentration. Moreover, some of the patients with higher BMI (≥ 24 kg/m²) met the goal trough concentration after an adjustment from 1000 mg every 12 h to 1000 mg every 8 h.

Conclusions

Serum vancomycin concentration decreases progressively with increasing BMI and the augmentation in CrCl in adult patients. The trough concentration of vancomycin should be continuously monitored for patients with a BMI ≥ 24 kg/m², and the dosage regimen should be adjusted to reach the target trough concentration in these patients to reduce the impact of BMI.

A Prospective Multicenter Clinical Observational Study on Vancomycin Efficiency and Safety With Therapeutic Drug Monitoring

Background

Vancomycin is a first-line antibiotic used for the treatment of severe gram-positive bacterial infections. Clinical guidelines recommend that the vancomycin trough concentration be 10-15 mg/L for regular infections and 15-20 mg/L for severe infections. We investigated whether increasing the vancomycin concentration would result in better clinical outcomes with sustainable adverse effects (AEs) in the Chinese population.

Methods

A prospective, open, multicenter clinical observational study was performed in patients with gram-positive bacterial infections from 13 teaching hospitals. Patients received vancomycin therapeutic drug monitoring. Clinical, microbiological, and laboratory data were collected.

Results

In total, 510 patients were enrolled, and 470 were evaluable, of whom 370 were adults and 100 were children; 35.53% had methicillin-resistant Staphylococcus aureus infections (vancomycin 50% minimum inhibitory concentration [MIC50] = 1, 90% minimum inhibitory concentration [MIC90] = 1), and 23.19% had Enterococcus species infections (vancomycin MIC50 = 1, MIC90 = 2). The average trough concentration was 10.54 ± 8.08 mg/L in adults and 6.74 ± 8.93 mg/L in children. The infection was eradicated in 86.22% of adults and 96% of children. Thirty-six vancomycin-related nephrotoxicity cases were reported in the enrolled population. No severe AEs or deaths were related to vancomycin therapy. Logistic regression analysis showed that trough concentration had no relationship with clinical outcomes (adults P = .75, children P = .68) but was correlated with adult nephrotoxicity (P < .0001). Vancomycin trough concentration had an applicable cut point at 13 mg/L.

Conclusions

Our study shows that vancomycin trough concentration has no statistical correlation with clinical outcomes, and is an indicator of nephrotoxicity in the observed population. We found no evidence that increasing vancomycin trough concentration to 15-20 mg/L can benefit Chinese patients with complicated infections.

Clinical Trials Registration

ChiCTR-OPC-16007920.

Model-based Evaluation of the Clinical and Microbiological Efficacy of Vancomycin: A Prospective Study of Chinese Adult In-house Patients

Background

Our aims in this prospective study were to evaluate the correlations between pharmacokinetic/pharmacodynamic (PK/PD) indices and the clinical/microbiological efficacy of vancomycin and to identify an appropriate PK/PD target in the Chinese population to guide vancomycin treatment in the clinic.

Methods

Adult patients from 11 hospitals in China with gram-positive infections who received vancomycin therapy for ≥5 days and who were under therapeutic drug monitoring (TDM) were enrolled in this study. A 1-compartment population PK model was established and validated. The correlations between PK/PD indices (Cmin, Cmax, 0-24 hour area under the curve (AUC0-24), and AUC0-24/minimum inhibitory concentration (MIC) and clinical outcomes (clinical efficacy and bacterial eradication) were evaluated.

Results

In total, 402 adult Chinese patients were enrolled. Among them, 380 patients were evaluable for PK analysis, and 334 were evaluable for PK/PD analysis. In the final population PK model, creatinine clearance (CLCR) was the significant covariate on CL (typical value, 3.87 L/hour; between-subject variability (BSV), 12.5%), and age was the significant covariate on volume of distribution (V) (typical value, 45.1 L; BSV, 24.8%). The univariate analysis showed that Cmax, AUC0-24, and AUC0-24/MIC were significantly different or marginally significantly different (P values were 0.009, 0.0385, and 0.0509, respectively) between microbiological outcome groups with coagulase-negative Staphylococcus infections. However, there were no significant differences (P > .05) in the above PK parameters by multivariate logistic regression analysis, indicating there was no independently associated factor.

Conclusions

No significant correlations were identified between PK/PD indices and the clinical or microbiological efficacy of vancomycin in Chinese patients. The necessity of vancomycin TDM based on trough concentration and the current treatment target of AUC0-24/MIC ≥400 need to be further evaluated and confirmed in additional prospective studies.

Development and comparison of population pharmacokinetic models of vancomycin in neurosurgical patients based on two different renal function markers

WHAT IS KNOWN AND OBJECTIVES

Some previous studies have indicated that serum cystatin C (Cys C) is a better marker than serum creatinine (SCR) for assessing the glomerular filtering rate (GFR). However, in almost all population pharmacokinetic models of vancomycin, the GFR is usually estimated from SCR. Therefore, the aim of this study was to compare the GFR estimated from SCR (sGFR) with the GFR estimated from Cys C (cGFR) and investigate which one can describe the characteristics of vancomycin population pharmacokinetics better in Chinese neurosurgical adult patients.

METHODS

Patients from the Neurosurgery Department aged ≥18 years were enrolled retrospectively. Among these patients, the data from 222 patients were used to establish two population pharmacokinetic models based on sGFR and cGFR, separately. The data from another 95 patients were used for the external validation of these two models. Non-linear mixed-effect modelling (NONMEM) 7.4.3 was used for the population pharmacokinetic analysis.

RESULTS

We developed two one-compartment models with first-order absorption based on Cys C and SCR, separately. In the Cys C model, age, body weight and cGFR were significant covariates on the clearance rate (CL) of vancomycin (typical value, 6.4 L/hour). In the SCR model, age and sGFR were significant covariates on the CL (typical value, 6.46 L/hour). The external validation results showed that the predictive performance of the two models was similar.

WHAT IS NEW AND CONCLUSION

In this study, the predictive performance of two models was similar in neurosurgical patients. We did not find a significant improvement in the predictive performance of the model when GFR was estimated from Cys C.

A population pharmacokinetic model of vancomycin for dose individualization based on serum cystatin C as a marker of renal function

OBJECTIVES

This study aimed to establish a vancomycin population pharmacokinetics (PPK) model based on serum cystatin C and to optimize dosing for achieving targeted steady-state trough concentrations (C_ss ) of 10-15 and 15-20 mg/l.

METHODS

Patients aged ≥18 years were prospectively enrolled. A vancomycin PPK model was built with glomerular filtration rate (GFR) as a renal covariate estimated by cystatin C. A new group of patients were used for external evaluation. PPK analysis and Monte Carlo simulations were performed using nonlinear mixed effect modelling programme.

KEY FINDINGS

Two hundreds of patients with 514 samples were included. The final model was CL (L/h) = (5.07 × (GFR/105.5)^0.524 × (AGE/48.5)^-0.309 × (WT/60)^0.491 ); V (l) = 46.3. Internal and external evaluations demonstrated good stability and predictability. The average probability of target attainment (PTA) of optimal dosing regimens for targeted C_ss achieving 10-15 and 15-20 mg/l were 51.2% and 40.6%, respectively. An average PTA ≥71% for targeted concentration of 10-20 mg/l was obtained.

CONCLUSIONS

A vancomycin PPK model with cystatin C as the renal marker has good stability and predictability. The new proposed dosing regimens were predicted to achieve a good PTA.

Pharmacokinetics of Vancomycin in Patients with Different Renal Function Levels

There are many determinants of vancomycin clearance, but these have not been analyzed separately in populations with different levels of renal function, which could be why some important factors have been missed. The aim of our study was to compare the pharmacokinetic parameters and factors that may affect vancomycin pharmacokinetics in groups of patients with normal renal function and in those with chronic kidney failure. The study used a population pharmacokinetic modeling approach, based on plasma vancomycin concentrations and other data from 78 patients with chronic kidney failure and 32 patients with normal renal function. The model was developed using NONMEM software and validated by bootstrapping. The final model for patients with impaired kidney function was described by the following equation: CL (L/h) = 0.284 + 0.000596 x DD + 0.00194 x AST, and that for the patients with normal kidney function by: CL (L/h) = 0.0727 + 0.205 x FIB. If our results are confirmed by new studies on two similar populations, these factors could be considered when dosing vancomycin in patients with chronically damaged kidneys, as well as in patients with normal kidneys who frequently require high doses of vancomycin.