Practice guidelines for therapeutic drug monitoring of vancomycin: a consensus review of the Japanese Society of Chemotherapy and the Japanese Society of Therapeutic Drug Monitoring

Time-to-recovery from severe pneumonia and its predictors among children 2-59 months of age admitted to the pediatric ward of Jimma University Medical Center, Southwest Ethiopia, 2023: A retrospective cohort study

BACKGROUND

Pneumonia is an inflammation of lung parenchyma. The World Health Organization estimated 156 million cases of pneumonia occur annually. Out of them, 20 million cases severe enough to require hospitalization, and each year 1.2 million deaths occur among under-five children. Despite studies and initiatives aimed at reducing pneumonia related deaths in children, Ethiopia is ranked sixth among top fifteen countries in terms of pneumonia related morbidity and mortality.

OBJECTIVES

This study aimed to assess the time to recovery from severe pneumonia and its predictors among children aged 2-59 months admitted to the pediatric ward of Jimma University Medical Center; Southwest, Ethiopia, 2023.

METHODS

A facility-based retrospective cohort study was carried out among 426 children aged between 2 and 59 months. Five years of medical records, from 2018-2022, were reviewed. A simple random sampling technique was used. Data entry was done in Epidata version 4.6 and exported to and analyzed by STATA version 15. Variables with p-value <  0.25 at Bivariable Cox regression analysis were selected for the multivariable Cox proportional model. A multivariable Cox regression model with 95% confidence interval and Adjusted Hazard Ratio was used to identify a significant predictor of time to recovery at a p-value <  0.05.

RESULT

The median recovery time was 4 days (IQR: 3, 7). Incidence rate of recovery was 15.78 per 100-person day (95% CI 14.2-17.5). The presence of co-morbidity (AHR; 0.7, 95% CI (0.54-0.91)), being treated with Ceftazidime and Vancomycin (AHR; 0.29, 95% CI (0.14-0.60)), antibiotic change (AHR; 0.74, 95% CI (0.58-0.95)) and late presentation to the Hospital (AHR; 0.58, 95% CI (0.43-0.78)) were statistically significant predictors that prolong recovery time.

CONCLUSION

The median recovery time was longer than other similar studies. Therefore, due attention should be given to the identified predictors of the recovery time.

Clinical validation of an innovative dried whole-blood spot method to quantify simultaneously vancomycin and creatinine in adult patients

BACKGROUND

A drawback of vancomycin use is the need for therapeutic drug monitoring and renal function monitoring. Traditional blood sampling involves drawing blood through a venepuncture. An alternative method, dried blood spot (DBS) sampling allows for self-sampling at home.

OBJECTIVES

To clinically validate a DBS method for simultaneous monitoring of vancomycin and creatinine.

METHODS

Hospitalized adults treated with intravenous vancomycin were included (trial registration NCT05257070). Blood sampling consisted of one venepuncture and one finger prick. Whole-blood DBS samples from patients were obtained by applying one drop of whole blood onto Whatman 903 filtrate paper. Bland-Altman analyses were used to assess the agreement and bias between the two measurements. Patients were asked to state their preferences for one of the two sampling methods.

RESULTS

The study involved a final analysis of 39 patient samples for the clinical validation of vancomycin and 46 patient samples for the clinical validation of creatinine. The difference between plasma and DBS concentrations was ≤20% for 77% of the vancomycin samples, the mean bias was -0.1379% (95% limit of agreement -5.899-5.623). The difference between plasma and DBS concentrations was ≤20% for 89% of the creatinine samples, the mean bias was 2.656% (95% limit of agreement -26.16-31.47). Most patients (18 out of 31) preferred a finger prick over a venepuncture and 12 patients indicated no preference.

CONCLUSIONS

This is the first study that successfully clinically validated a DBS sampling method for simultaneous measurement of vancomycin and creatinine, allowing for direct use in (outpatient) practice.

A case of meningitis treated with intraventricular vancomycin in an infant

There is limited evidence for vancomycin (VCM) ventriculoperitoneal (VP) administration. We report a 3-month-old female with congenital hydrocephalus who developed a fever and was admitted to the hospital with a suspected VP shunt infection; she was being managed as an outpatient following VP shunt placement. Methicillin-resistant Staphylococcus aureus was detected on the removed catheter tip, and VCM treatment was initiated. Intravenous administration was ineffective, so intraventricular administration was initiated. Therapeutic drug monitoring (TDM) of cerebrospinal fluid (CSF) drug concentration showed a high trough level (30.9-50.0 μg/mL) at 2 mg daily dosing. Dose adjustment was implemented considering CSF drainage volume, and administration was changed to every other day. This case suggests that performing TDM and considering the amount of CSF drainage when establishing a detailed dosing regimen are important when administering VCM intraventricularly.

Mitigating Risk of Acute Kidney Injury Among Children With Methicillin-resistant Staphylococcus aureus Osteomyelitis

OBJECTIVE

Children with acute hematogenous osteomyelitis (AHO) from methicillin-resistant Staphylococcus aureus (MRSA) are treated with vancomycin despite the risk of acute kidney injury (AKI). This study evaluates the rate of AKI and resource utilization for children with or without AKI when vancomycin is used in this setting.

METHODS

Children with MRSA AHO treated with vancomycin were retrospectively studied. AKI was assessed by clinical diagnosis and Kidney Disease Improving Global Outcomes (KDIGO) criteria. Cohorts of children with or without AKI were compared for differences in treatment, resource utilization, and outcomes. Multivariate logistic regression analysis assessed factors associated with risk for AKI. Cost analysis was performed using the Pediatric Health Information System and Healthcare Cost and Utilization Project databases.

RESULTS

Among 85 children studied, 14 (16.5%) had chart-diagnosed AKI and 24 (28.2%) met KDIGO criteria. Children with AKI had more febrile days and higher thrombosis rates. They had longer vancomycin treatment (8 vs 5 d), higher troughs (27.8 vs 17.5 mg/L), and prolonged hospitalization (19.9 vs 11.1 d). Multivariate analysis found a maximum vancomycin trough level (odds ratio: 1.05, P = 0.003) with a cutoff of 21.7 mg/L predicted AKI.Only 2 of 20 (10%) children who had MRSA isolates with a minimum inhibitory concentration of 2 achieved therapeutic vancomycin levels. Pediatric Health Information System data of 3133 children with AHO treated with vancomycin identified 75 (2.4%) with AKI who had significantly longer lengths of stay (13 vs 7 d) and higher billed charges ($117K vs $51K) than children without AKI.

CONCLUSIONS

Chart documentation of AKI (16.5%) grossly underestimated KDIGO-defined occurrence (28.2%). This study showed that vancomycin-associated AKI required substantially greater resource utilization and higher health care costs. Lowering the targeted trough range, shortening the duration of vancomycin therapy, and considering alternative antibiotics when minimum inhibitory concentration ≥2 will reduce the risk and cost of AKI among children with MRSA AHO.

LEVEL OF EVIDENCE

Level III-retrospective comparative therapeutic study.

Factors Affecting Vancomycin Trough Concentration; a Population Pharmacokinetic Model in Non-Critical Care Saudi Patients

Background and Objective

Vancomycin is commonly prescribed in treatment of methicillin-resistant Staphylococcus aureus infections. While, vancomycins' pharmacokinetic vary among older patients, there is a paucity of data regarding specific characteristics influencing pharmacokinetics in Saudi adult patients. This study aims to establish a population-pharmacokinetic (Pop-PK) model for vancomycin in patients admitted to medical wards, with the focus on identification of patient characteristics influencing vancomycin trough concentrations.

Methods

A multicenter retrospective study was conducted involving patients aged ≥40 years admitted to medical wards in the Eastern Province, Saudi Arabia and initiated on vancomycin, between January to December 2022. Non-linear mixed-effects modelling (Monolix) was employed to develop the Pop-PK model. A base model was selected based on the Akaike information criterion. Covariates considered included age, sex, body weight, C-reactive protein (CRP), serum creatinine, creatinine clearance (CrCl), and albumin levels. A P-value of <0.05 was considered statistically significant for inclusion of covariates in the final model by stepwise addition. The simulation performance of the model was assessed by visual predictive check plot. The final model was simulated using Simulx software to assess the effect of the included covariates on vancomycin trough concentration.

Results

A total of 172 vancomycin trough concentrations from 124 patients were analyzed. The final Pop-PK model characterized vancomycin trough concentrations was one compartment distribution with linear elimination. CrCl and CRP were the only covariates included in the final model, as they reduced the between-subject variability (BSV) for clearance (from 173% to 81%). The simulated model demonstrated that high CRP value and low CrCl contributed to increased vancomycin trough concentrations.

Conclusion

This study highlights large BSV in trough concentrations among patients and emphasizes the influencing of CrCl and CRP on vancomycin pharmacokinetics in medical care settings.

Identification of Patients Who Require Two-Point Blood Sampling for the Peak and Trough Values Rather Than One-Point Blood Sampling for the Trough Value for the Evaluation of AUC of Vancomycin Using Bayesian Estimation

OBJECTIVES

It is recommended to adjust the dose of vancomycin (VCM) with a target area under the concentration-time curve (AUC) of 400-600 μg·h/mL. Factors that affect the deviation between AUCs are estimated from the trough value alone and the trough and peak values using practical AUC-guided therapeutic drug monitoring (PAT) for vancomycin. In this study, factors that affect AUC were evaluated.

METHODS

AUCs were estimated from a single trough value and trough and peak values, and the patients were classified into those who showed a 10% or greater deviation (deviation group) and those in whom the deviation was less than 10% (no-deviation group). Risk factors related to ≥ 10% deviation of AUC were identified by univariate and multivariate analysis.

RESULTS

As a result of univariate and multivariate analysis of 30 patients in the deviation group and 344 patients in the no-deviation group, a creatinine clearance (CLcr) of ≥ 110 mL/min (odds ratio (OR) = 3.697, 95% confidence interval (CI) = 1.616-8.457, p = 0.002), heart failure with a brain natriuretic peptide (BNP) of ≥ 300 pg/mL (OR = 4.854, 95%CI = 1.199-19.656, p = 0.027), and the concomitant use of angiotensin converting enzyme inhibitor or angiotensin II receptor blocker (ACE-I/ARB) (OR = 2.544, 95%CI = 1.074-6.024, p = 0.034) were identified as risk factors of ≥ 10% deviation of AUC.

CONCLUSIONS

Estimation of AUC by two-point blood sampling for the trough and peak values rather than one-point blood sampling for the trough value is suggested to improve the prediction accuracy in patients with enhanced renal function, severe heart failure, and patients using ACE-I/ARB.

Impact of the First Twenty-Four-Hour Area Under the Concentration-Time Curve/Minimum Inhibitory Concentration of Vancomycin on Treatment Outcomes in Patients With Methicillin-Resistant Staphylococcus aureus Bacteremia

Background

Vancomycin regimens are designed to achieve an area under the concentration-time curve/minimum inhibitory concentration (AUC/MIC) ratio ranging between 400 and 600 µg·h/mL in the steady state. However, in cases of critical infections such as bacteremia requiring an early treatment approach, the clinical course may be affected by the AUC/MIC before reaching the steady state, that is, the AUC/MIC values 24 h after the first dose (first 24-h AUC/MIC). This study evaluated the relationship between the first 24-h AUC/MIC and the clinical course of methicillin-resistant Staphylococcus aureus (MRSA) infection.

Methods

We retrospectively reviewed the records of patients with MRSA bacteremia in a university hospital between 2015 and 2022. The first 24-h AUC/MIC cutoff was set at 300 µg·h/mL based on the results of early response, and eligible patients were divided into groups with a first 24-h AUC/MIC either < 300 µg·h/mL (< 300 group, n = 32) or ≥ 300 µg·h/mL (≥ 300 group, n = 38). The primary endpoint was the rate of treatment efficacy, and the secondary endpoints were time to clinical and bacteriological improvement and 30-day survival rate.

Results

Treatment efficacy and 30-day survival rates were not significantly different between the two groups (78.1% vs. 79.0%, P = 0.933 and 83.9% vs. 87.2%, P = 0.674, respectively). Among patients who showed treatment efficacy, the median time to clinical and bacteriological improvement was 11.5 days and 8.0 days in the < 300 and ≥ 300 groups, respectively; compared to the ≥ 300 group, the < 300 group had a significantly longer time to improvement (P = 0.001).

Conclusions

The first 24-h AUC/MIC had no effect on the treatment efficacy and 30-day survival rates. However, the time to clinical and bacteriological improvement was significantly prolonged in the < 300 group, indicating that the first 24-h AUC/MIC does not affect the rate of therapeutic efficacy but may affect the treatment period.

Optimizing vancomycin therapeutic drug monitoring compliance in pediatric oncology: towards personalized medication management

Aim: Vancomycin, a crucial treatment for Gram-positive bacteria, necessitates therapeutic drug monitoring (TDM) to prevent treatment failures. We investigated the healthcare professional's compliance toward TDM of vancomycin recommendations and follow-up levels. Materials & methods: We collected data from 485 patients who received vancomycin in the Children's Cancer Hospital Egypt 57357 medical records system (Cerner) over 4 months, from January to April 2020. Results: Our data shows that only 54% of patients had TDM requests from healthcare professionals for the total patients who received vancomycin treatment. The healthcare professionals' compliance with the recommendations was 91.7%, while the follow-up levels were 66.7%. Conclusion: While overall adherence to recommendations is strong, enhancing compliance with follow-up levels remains a priority for improvement.

Predictive Value of Vancomycin AUC24/MIC Ratio for 30-day Mortality in Patients with Severe or Complicated Methicillin-Resistant Staphylococcus aureus Infections: A Multicenter Retrospective Study

BACKGROUND

Although vancomycin is typically employed against methicillin-resistant Staphylococcus aureus (MRSA) infections, the optimal ratio of 24-h area under the concentration-time curve to minimum inhibitory concentration (AUC24/MIC) for severe or complicated infections lacks clear guideline recommendations. This study aimed to determine the target AUC24/MIC ratio associated with treatment outcomes of infections treated with vancomycin.

METHODS

This retrospective multicenter cohort study included adult patients receiving ≥ 5 days of vancomycin for severe/complicated MRSA infections (e.g., osteoarticular, pulmonary, endocarditis, etc.) between January 2018 and December 2023. The primary outcome was 30-day mortality, with secondary outcomes including clinical success, microbiological eradication, and nephrotoxicity. Receiver operating characteristic (ROC) curve analysis was used to identify the AUC24/MIC cutoff for 30-day mortality. Multivariate regression analysis was used to determine association between AUC24/MIC and outcomes.

RESULTS

This study included 82 patients. ROC identified a target AUC24/MIC of ≥ 505 for 30-day mortality. The overall 30-day mortality rate (22.0%) was significantly higher for below average AUC24/MIC cutoff (34.1%) than for above AUC24/MIC cutoff group (9.8%). Multivariate analysis confirmed AUC24/MIC of < 505 as an independent predictor (adjusted odds ratio, 5.001; 95% confidence interval, 1.335-18.75). The clinical success rate differed significantly between below- and above-cutoff groups, whereas microbiological eradication tended to favor the above-cutoff group. The nephrotoxicity rates were comparable between groups.

CONCLUSIONS

In treating severe/complicated MRSA infections, vancomycin AUC24/MIC ratio ≥ 505 was independently associated with favorable 30-day mortality. Given the retrospective nature of this study, further prospective studies are essential to confirm the reliability of the target AUC24/MIC ratios.

Flowchart for predicting achieving the target area under the concentration-time curve of vancomycin in critically ill Japanese patients: A multicenter retrospective study

INTRODUCTION

In therapeutic drug monitoring (TDM) of vancomycin (VCM), the area under the concentration-time curve (AUC) is related to the clinical efficacy and toxicity. Therefore, herein, we examined the factors associated with achieving the target AUC at follow-up and developed a decision flowchart for achieving the target AUC in critically ill patients.

METHODS

This multicenter retrospective observational study was conducted at eight hospitals. We retrospectively analyzed data from patients who had received VCM in the intensive care unit from January 2020 to December 2022. Decision-tree (DT) analysis was performed using factors with p < 0.1 in univariate analysis as the independent variables. Case data were split up to two times, and four subgroups were included. The primary endpoint was achieving the target AUC at the follow-up TDM (AUCfollow-up) and target AUCfollow-up achievement was defined as an AUC of 400-600 μg‧h/mL. The initial AUC values were calculated with the 2-point concentrations (peak and trough) using the Bayesian estimation software Practical AUC-guided TDM (PAT).

RESULTS

Among 70 patients (median age [interquartile range], 66 [56, 79] years; 50 % women), the AUCfollow-up was achieved in 70 % (49/70). Three factors were selected for the decision flow chart: predicted AUCfollow-up of 400-600 μg‧h/mL, dosing at 12-h intervals, and CCr of 130 mL/min/1.73 m2 or higher; the accuracy was adequate (92 %, R2 0.52).

CONCLUSION

We successfully identified the factors associated with achieving the target AUC of VCM at follow-up TDM and developed a simple-to-use DT model. However, the validity of the findings needs to be evaluated.

Dried blood spot analysis for the quantification of vancomycin and creatinine using liquid chromatography - tandem mass spectrometry: Method development and validation

BACKGROUND

Vancomycin is a widely used antibiotic for the treatment of gram-positive bacterial infections, especially for methicillin-resistant Staphylococcus aureus (MRSA) infections. Due to a small therapeutic range and large inter-patient variability, therapeutic drug monitoring (TDM) of vancomycin is required to minimize toxicity and maximize treatment efficacy. Venous blood sampling is mostly applied for TDM of vancomycin, although this widely used sampling method is more invasive compared to less painful alternatives, such as the dried blood spot (DBS) method, which can be performed at home.

METHOD

We developed an UPLC-MS/MS method for the quantification of vancomycin and creatinine in DBS. A fast sample preparation and short analysis run time of 5.2 min were applied, which makes this method highly suitable for clinical settings. Validation was performed according to international (FDA and EMA) guidelines.

RESULTS

The validated concentration range was found linear for creatinine from 41.8 µmol/L to 722 µmol/L and for vancomycin from 3.8 mg/L to 76.6 mg/L (r2 > 0.990) and the inaccuracies, imprecisions, hematocrit effects, and recoveries were < 15 % for both compounds. No significant carryover effect was observed.

CONCLUSION

Hence, we successfully validated a quantification method for the simultaneous determination of creatinine and vancomycin in DBS.

Antimicrobial Multidrug Resistance: Clinical Implications for Infection Management in Critically Ill Patients

The increasing incidence of antimicrobial resistance (AMR) worldwide represents a serious threat in the management of sepsis. Due to resistance to the most common antimicrobials prescribed, multidrug-resistant (MDR) pathogens have been associated with delays in adequate antimicrobial therapy leading to significant increases in mortality, along with prolonged hospital length of stay (LOS) and increases in healthcare costs. In response to MDR infections and the delay of microbiological results, broad-spectrum antibiotics are frequently used in empirical antimicrobial therapy. This can contribute to the overuse and misuse of antibiotics, further promoting the development of resistance. Multiple measures have been suggested to combat AMR. This review will focus on describing the epidemiology and trends concerning MDR pathogens. Additionally, it will explore the crucial aspects of identifying patients susceptible to MDR infections and optimizing antimicrobial drug dosing, which are both pivotal considerations in the fight against AMR. Expert commentary: The increasing AMR in ICUs worldwide makes the empirical antibiotic therapy challenging in septic patients. An AMR surveillance program together with improvements in MDR identification based on patient risk stratification and molecular rapid diagnostic tools may further help tailoring antimicrobial therapies and avoid unnecessary broad-spectrum antibiotics. Continuous infusions of antibiotics, therapeutic drug monitoring (TDM)-based dosing regimens and combination therapy may contribute to optimizing antimicrobial therapy and limiting the emergence of resistance.

Status and Quality of Guidelines for Therapeutic Drug Monitoring Based on AGREE II Instrument

BACKGROUND

With the progress of therapeutic drug monitoring (TDM) technology and the development of evidence-based medicine, many guidelines were developed and implemented in recent decades.

OBJECTIVE

The aim was to evaluate the current status of TDM guidelines and provide suggestions for their development and updates based on Appraisal of Guidelines for Research and Evaluation (AGREE) II.

METHODS

The TDM guidelines were systematically searched for among databases including PubMed, Embase, China National Knowledge Infrastructure, Wanfang Data, and the Chinese biomedical literature service system and the official websites of TDM-related associations. The search period was from inception to 6 April 2023. Four researchers independently screened the literature and extracted data. Any disagreement was discussed and reconciled by another researcher. The quality of guidelines was assessed using the AGREE II instrument.

RESULTS

A total of 92 guidelines were included, including 57 technical guidelines, three management guidelines, and 32 comprehensive guidelines. The number of TDM guidelines has gradually increased since 1979. The United States published the most guidelines (20 guidelines), followed by China (15 guidelines) and the United Kingdom (ten guidelines), and 23 guidelines were developed by international organizations. Most guidelines are aimed at adult patients only, while 28 guidelines include special populations. With respect to formulation methods, there are 23 evidence-based guidelines. As for quality evaluation results based on AGREE II, comprehensive guidelines scored higher (58.16%) than technical guidelines (51.36%) and administrative guidelines (50.00%).

CONCLUSION

The number of TDM guidelines, especially technical and comprehensive ones, has significantly increased in recent years. Most guidelines are confronted with the problems of unclear methodology and low quality of evidence according to AGREE II. More evidence-based research on TDM and high-quality guideline development is recommended to promote individualized therapy.

Population pharmacokinetic model and dosing optimization of vancomycin in hematologic malignancies with neutropenia and augmented renal clearance

AIM

Data on the pharmacokinetics (PK) and area under the curve (AUC)-based dosing strategy of vancomycin (VCM) in hematologic malignancies are limited. According to our preliminary narrative review, only a few population PK analyses in hematologic malignancies have been performed. Therefore, we aimed to develop a population PK model, investigate the factors influencing VCM PK, and propose an optimal dosing regimen for hematologic malignancies.

METHODS

A retrospective study was conducted in patients with underlying hematologic malignancies treated with VCM. A total of 148 patients were enrolled for population PK modeling. Simulation analyses were performed to identify dosing regimens achieving a target exposure of AUC_0-24 of 400-600 mg h/L at the steady-state.

RESULTS

The VCM PK data were best described with a one-compartment model. Significant covariates included creatinine clearance (Ccr), diagnosis of acute myeloid leukemia (AML) and neutropenia on VCM clearance (CL), and body weight (WT) on the volume of distribution (Vd). The typical values of CL and Vd were 3.09 L/h (normalized to Ccr value of 90 mL/min) and 122 L/70 kg, respectively. Concerning the effect on VCM dosing, AML patients required 15% higher doses than non-AML patients, independently of renal function. In contrast, for neutropenic patients, only those with augmented renal clearance (ARC, Ccr value ≥ 130 mL/min) required a 10% dose increase compared to non-neutropenic patients.

CONCLUSION

AML patients with neutropenia and ARC represent a critical population with a higher risk of VCM underexposure. Thus, individualized dosing adjustment and therapeutic drug monitoring are strongly recommended.

Development and Evaluation of a Novel Software Program, SAKURA-TDM, for Area Under the Concentration-Time Curve-Guided Vancomycin Dosing: A Short Communication

BACKGROUND

The area under the concentration-time curve (AUC)-guided dosing of vancomycin has been introduced in Japan; however, the optimal dosing method remains controversial. Here, a novel software program was developed for AUC-guided vancomycin dosing and to estimate the theoretical threshold of the steady-state AUC 24 that could reduce the risk of renal injury.

METHODS

A single-center, retrospective, observational study was conducted to develop a novel software program (SAKURA-TDM ver.1.0) for AUC-guided dosing. The estimation accuracy of pharmacokinetic parameters determined using SAKURA-TDM was compared with that of clinically available software programs and assessed with Bland-Altman analysis. In addition, theoretical cutoff points of the steady-state AUC 24 and the predicted trough values were estimated using Youden J statistic approach.

RESULTS

The estimation accuracy of pharmacokinetic parameters and AUC determined using SAKURA-TDM was comparable to that of other TDM software programs. Of note, despite a good relationship between the predicted AUC 24 and trough values, the correlation between the predicted AUC 24 and measured trough values was not strong. The cutoff values of the steady-state AUC 24 and the predicted trough value for reducing the probability of a measured trough value of >20 mcg/mL were 513.1 mg·h/L and 15.6 mcg/mL, respectively.

CONCLUSIONS

We demonstrated the equivalence of the estimated PK parameters between SAKURA-TDM and other TDM software programs available in Japan. Considering the threshold of both trough values and the steady-state AUC and monitoring of the AUC in a non-steady state, it would be possible to reduce the risk of vancomycin-associated renal injury.

High-Performance Liquid Chromatography for Ultra-Simple Determination of Plasma Voriconazole Concentration

Voriconazole is an antifungal drug used to treat invasive aspergillosis. Voriconazole exhibits nonlinear behavior and considerable individual variability in its pharmacokinetic profile. Invasive aspergillosis has a poor prognosis, and failure of treatment owing to low voriconazole blood levels is undesirable. Thus, therapeutic drug monitoring (TDM) of voriconazole is recommended. However, plasma voriconazole concentration is rarely measured in hospitals, and the TDM of voriconazole is not widely practiced in Japan. We aimed to develop an ultra-simple method to measure plasma voriconazole concentration. Ten microliters of plasma sample was extracted, and proteins were precipitated using methanol extraction. Voriconazole and ketoconazole (internal standard) were separated using high-performance liquid chromatography. A calibration curve was prepared, which was linear over plasma voriconazole concentrations of 0.125−12.5 µg/mL, with a coefficient of determination of 0.9999. The intra-day and inter-day validation coefficients were 0.9−2.2% and 1.3−6.1%, respectively. The assay accuracy was −4.2% to 1.6%, and recovery was >97.8%. Our ultra-simple, sensitive, and inexpensive high-performance liquid chromatography ultraviolet method to determine plasma voriconazole concentration will help improve the voriconazole TDM implementation rate and contribute to effective and safe voriconazole use.

Influence of pharmacists and infection control teams or antimicrobial stewardship teams on the safety and efficacy of vancomycin: A Japanese administrative claims database study

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) has a high mortality and requires effective treatment with anti-MRSA agents such as vancomycin (VCM). Management of the efficacy and safety of VCM has been implemented with the assignment of pharmacists in hospital wards and the establishment of teams related to infectious diseases. However, there are no reports evaluating the association between these factors and the efficacy and safety of VCM in large populations.

Methods

This study used the Japanese administrative claims database accumulated from 2010 to 2019. The population was divided into two groups, therapeutic drug monitoring (TDM) group and non-TDM group, and adjusted by propensity score matching. We performed multivariate logistic regression analysis to determine the influence of pharmacists and infection control teams or antimicrobial stewardship teams on acute kidney injury (AKI) and 30-day mortality.

Results

The total number of patients was 73 478 (TDM group, n = 55 269; non-TDM group, n = 18 209). After propensity score matching, 18 196 patients were matched in each group. Multivariate logistic regression analysis showed that pharmacological management for each patient contributed to the reduction of AKI (odds ratio [OR]: 0.812, 95% confidence interval [CI]: 0.723‒0.912) and 30-day mortality (OR: 0.538, 95% CI: 0.503‒0.575). However, the establishment of infectious disease associated team in facilities and the assignment of pharmacists in the hospital wards had no effect on AKI and 30-day mortality. In addition, TDM did not affect the reduction in AKI (OR: 1.061, 95% CI: 0.948‒1.187), but reduced 30-day mortality (OR: 0.873, 95% CI: 0.821‒0.929).

Conclusion

Pharmacologic management for individual patients, rather than assignment systems at facilities, is effective to reduce AKI and 30-day mortality with VCM administration.

Assessment of an institutional guideline for vancomycin dosing and identification of predictive factors associated with dose and drug trough levels

OBJECTIVES

To evaluate the effectiveness of an antimicrobial guideline for vancomycin prescribing deployed using electronic prescribing aid and web/phone-based app. To define factors associated with guideline compliance and drug levels, and to investigate if antimicrobial dosing recommendations can be refined using routinely collected electronic healthcare record data.

METHODS

We used data from Oxford University Hospitals between 01-January-2016 and 01-June-2021 and multivariable regression models to investigate factors associated with dosing compliance, drug levels and acute kidney injury (AKI).

RESULTS

3767 patients received intravenous vancomycin for ≥24 h. Compliance with recommended loading and initial maintenance doses reached 84% and 70% respectively; 72% of subsequent maintenance doses were correctly adjusted. However, only 26% first and 32% subsequent levels reached the target range, and for patients with ongoing vancomycin treatment, 55-63% achieved target levels at 5 days. Drug levels were independently higher in older patients. Incidence of AKI was low (5.7%). Model estimates were used to propose updated age, weight and eGFR specific guidelines.

CONCLUSION

Despite good compliance with guidelines for vancomycin dosing, the proportion of drug levels achieving the target range remained suboptimal. Routinely collected electronic data can be used at scale to inform pharmacokinetic studies and could improve vancomycin dosing.

Review and evaluation of vancomycin dosing guidelines for obese individuals

INTRODUCTION

Vancomycin dosing decisions are informed by factors such as body weight and renal function. It is important to understand the impact of obesity on vancomycin pharmacokinetics and how this may influence dosing decisions. Vancomycin dosing guidelines use varied descriptors of body weight and renal function. There is uncertainty whether current dosing guidelines result in attainment of therapeutic targets in obese individuals.

AREAS COVERED

Literature was explored using PubMed, Embase and Google Scholar for articles from January 1980 to July 2021 regarding obesity-driven physiological changes, their influence on vancomycin pharmacokinetics and body size descriptors and renal function calculations in vancomycin dosing. Pharmacokinetic simulations reflective of international vancomycin dosing guidelines were conducted to evaluate the ability of using total, ideal and adjusted body weight, as well as Cockcroft-Gault and CKD-EPI equations to attain an area-under-the-curve to minimum inhibitory concentration ratio (AUC₂₄/MIC) target (400-650) in obese individuals.

EXPERT OPINION

Vancomycin pharmacokinetics in obese individuals remains debated. Guidelines that determine loading doses using total body weight, and maintenance doses adjusted based on renal function and adjusted body weight, may be most appropriate for obese individuals. Use of ideal body weight leads to subtherapeutic vancomycin exposure and underestimation of renal function.

Target Therapeutic Ranges of Anti-MRSA Drugs, Linezolid, Tedizolid and Daptomycin, and the Necessity of TDM

The target therapeutic ranges of vancomycin, teicoplanin, and arbekacin have been determined, and therapeutic drug monitoring (TDM) is performed in clinical practice. However, TDM is not obligatory for daptomycin, linezolid, or tedizolid. In this study, we examined whether TDM will be necessary for these 3 drugs in the future. There was no significant difference in therapeutic effects on acute bacterial skin and skin structure infection between linezolid and tedizolid by meta-analysis. Concerning the therapeutic effects on pneumonia, the rate of effectiveness after treatment with tedizolid was significantly lower than with linezolid. With respect to safety, the incidences of gastrointestinal adverse events and blood/lymphatic system disorders related to tedizolid were significantly lower than those related to linezolid. Linezolid exhibits potent therapeutic effects on pneumonia, but the appearance of adverse reactions is indicated as a problem. There was a dose-dependent decrease in the platelet count, and the target trough concentration (C_trough) was estimated to be 4-6 or 2-7 µg/mL in accordance with the patient's condition. The efficacy of linezolid may be obtained while minimizing the appearance of adverse reactions by performing TDM. The target therapeutic range of tedizolid cannot be achieved in immunocompromised or severe patients. Therefore, we concluded that TDM was unnecessary, considering step-down therapy with oral drugs, use in non-severe patients, and high-level safety. Concerning daptomycin, high-dose administration is necessary to achieve an area under the curve (AUC) of ≥666 as an index of efficacy. To secure its safety, C_trough (<20 µg/mL) monitoring is important. Therefore, TDM is necessary.

Antimicrobial safety considerations in critically ill patients: part I: focused on acute kidney injury

INTRODUCTION

Antibiotic prescription is a challenging issue in critical care settings. Different pharmacokinetic and pharmacodynamic properties, polypharmacy, drug interactions, and high incidence of multidrug-resistant microorganisms in this population can influence the selection, safety, and efficacy of prescribed antibiotics.

AREAS COVERED

In the current article, we searched PubMed, Scopus, and Google Scholar for estimating renal function in acute kidney injury, nephrotoxicity of commonly used antibiotics, and nephrotoxin stewardship in intensive care units.

EXPERT OPINION

Early estimation of kidney function with an accurate method may be helpful to optimize antimicrobial treatment in critically ill patients. Different antibiotic dosing regimens may be required for patients with acute kidney injury. In many low-resource settings, therapeutic drug monitoring is not available for antibiotics. Acute kidney injury may influence treatment effectiveness and patient outcome.

A Retrospective Study on the Effectiveness and Safety of Vancomycin versus Daptomycin in Hemodialysis Patients

Vancomycin or daptomycin is administered to hemodialysis patients infected with methicillin-resistant Staphylococcus and Enterococcus species. Although serious concerns regarding nephrotoxicity due to vancomycin have been raised, it might not be a critical issue in hemodialysis patients. Moreover, very few studies have investigated the effectiveness of vancomycin versus daptomycin in patients undergoing hemodialysis. Hence, we retrospectively evaluated the effectiveness and safety of vancomycin and daptomycin in patients undergoing hemodialysis. We investigated the following measures: mortality, clinical and microbiological effectiveness, and incidence of adverse events in hemodialysis patients who received vancomycin or daptomycin from 2014 to 2019. Moreover, we evaluated the covariates related to 30-day mortality. We found that 73 patients received vancomycin, while 34 received daptomycin for the treatment of infections due to methicillin-resistant Staphylococcus aureus, methicillin-resistant coagulase-negative Staphylococci, and Enterococcus faecium. Mortality after vancomycin treatment was significantly lower than daptomycin treatment (4.1% vs. 26.5%, p < 0.01). The clinical and microbiological effectiveness as well as the safety were not significantly different between the two treatments. Although daptomycin treatment with a loading dose was associated with lower mortality, the mortality of the treatment (8.3%) did not differ significantly compared to that of the vancomycin treatment (4.1%). Therefore, our findings suggest that vancomycin remains the first-line treatment for hemodialysis patients; however, a loading dose may be beneficial for patients receiving daptomycin.

Does the cytokine adsorber CytoSorb® reduce vancomycin exposure in critically ill patients with sepsis or septic shock? a prospective observational study

BACKGROUND

Hemadsorption of cytokines is used in critically ill patients with sepsis or septic shock. Concerns have been raised that the cytokine adsorber CytoSorb^® unintentionally adsorbs vancomycin. This study aimed to quantify vancomycin elimination by CytoSorb^®.

METHODS

Critically ill patients with sepsis or septic shock receiving continuous renal replacement therapy and CytoSorb^® treatment during a prospective observational study were included in the analysis. Vancomycin pharmacokinetics was characterized using population pharmacokinetic modeling. Adsorption of vancomycin by the CytoSorb^® was investigated as linear or saturable process. The final model was used to derive dosing recommendations based on stochastic simulations.

RESULTS

20 CytoSorb^® treatments in 7 patients (160 serum samples/24 during CytoSorb^®-treatment, all continuous infusion) were included in the study. A classical one-compartment model, including effluent flow rate of the continuous hemodialysis as linear covariate on clearance, best described the measured concentrations (without CytoSorb^®). Significant adsorption with a linear decrease during CytoSorb^® treatment was identified (p < 0.0001) and revealed a maximum increase in vancomycin clearance of 291% (initially after CytoSorb^® installation) and a maximum adsorption capacity of 572 mg. For a representative patient of our cohort a reduction of the area under the curve (AUC) by 93 mg/L*24 h during CytoSorb^® treatment was observed. The additional administration of 500 mg vancomycin over 2 h during CytoSorb^® attenuated the effect and revealed a negligible reduction of the AUC by 4 mg/L*24 h.

CONCLUSION

We recommend the infusion of 500 mg vancomycin over 2 h during CytoSorb^® treatment to avoid subtherapeutic concentrations. Trial registration NCT03985605. Registered 14 June 2019, https://clinicaltrials.gov/ct2/show/NCT03985605.

Optimizing Antimicrobial Dosing for Critically Ill Patients with MRSA Infections: A New Paradigm for Improving Efficacy during Continuous Renal Replacement Therapy

The dosage regimen of vancomycin, teicoplanin and daptomycin remains controversial for critically ill patients undergoing continuous renal replacement therapy (CRRT). Monte Carlo simulation was applied to identify the optimal regimens of antimicrobial agents in patients with methicillin-resistant Staphylococcus aureus (MRSA) infections based on the mechanisms of different CRRT modalities on drug clearance. The optimal vancomycin dosage for patients received a CRRT doses ≤ 30 mL/kg/h was 20 mg/kg loading dose followed by 500 mg every 8 h, while 1 g every 12 h was appropriate when 35 mL/kg/h was prescribed. The optimal teicoplanin dosage under a CRRT dose ≤ 25 mL/kg/h was four loading doses of 10 mg/kg every 12 h followed by 10 mg/kg every 48 h, 8 mg/kg every 24 h and 6 mg/kg every 24 h for continuous veno-venous hemofiltration, continuous veno-venous hemodialysis and continuous veno-venous hemodiafiltration, respectively. When the CRRT dose increased to 30–35 mL/kg/h, the teicoplanin dosage should be increased by 30%. The recommended regimen for daptomycin was 6–8 mg/kg every 24 h under a CRRT dose ≤ 25 mL/kg/h, while 8–10 mg/kg every 24 h was optimal under 30–35 mg/kg/h. The CRRT dose has an impact on probability of target attainment and CRRT modality only influences teicoplanin.

Pharmacokinetics and pharmacodynamics of peptide antibiotics

Antimicrobial resistance is a major global health challenge. As few new efficacious antibiotics will become available in the near future, peptide antibiotics continue to be major therapeutic options for treating infections caused by multidrug-resistant pathogens. Rational use of antibiotics requires optimisation of the pharmacokinetics and pharmacodynamics for the treatment of different types of infections. Toxicodynamics must also be considered to improve the safety of antibiotic use and, where appropriate, to guide therapeutic drug monitoring. This review focuses on the pharmacokinetics/pharmacodynamics/toxicodynamics of peptide antibiotics against multidrug-resistant Gram-negative and Gram-positive pathogens. Optimising antibiotic exposure at the infection site is essential for improving their efficacy and minimising emergence of resistance.

A Systematic Review on Clinical Safety and Efficacy of Vancomycin Loading Dose in Critically Ill Patients

Background: The clinical significance of utilizing a vancomycin loading dose in critically ill patients remains unclear. Objective: The main aim of this systematic review is to evaluate the clinical safety and efficacy of the vancomycin loading dose in critically ill patients. Methods: We performed a systematic review using PRISMA guidelines. PubMed, the Web of Science, MEDLINE, Scopus, Google Scholar, the Saudi Digital Library and other databases were searched. Studies that reported clinical outcomes among patients receiving the vancomycin LD were considered eligible. Data for this study were collected using PubMed, the Web of Science, MEDLINE, Scopus, Google Scholar and the Saudi Digital Library using the following terms: “vancomycin”, “safety”, “efficacy” and “loading dose” combined with the Boolean operator “AND” or “OR”. Results: A total of 17 articles, including 2 RCTs, 11 retrospective cohorts and 4 other studies, met the inclusion/exclusion criteria out of a total 1189 studies. Patients had different clinical characteristics representing a heterogenous group, including patients in critical condition, with renal impairment, sepsis, MRSA infection and hospitalized patients for hemodialysis or in the emergency department. Conclusions: The study shows that the target therapeutic level is achieved more easily among patients receiving a weight-based LD as compared to patients received the usual dose without an increased risk of new-onset adverse drug reactions.

A Case of Persistent Bacillus cereus Bacteremia Responding to a Combination of Vancomycin and Gentamicin

A 56-year-old woman with a history of connective tissue disease developed fever, and Bacillus cereus (B. cereus) was detected in blood cultures. Therefore, treatment with vancomycin (VCM) was initiated. Since her blood cultures persistently detected B. cereus despite peripheral intravenous catheter replacement and VCM treatment, concomitant treatment with gentamicin (GM) was started. Blood cultures then became negative. Persistent B. cereus bacteremia responded to combination therapy with VCM and GM. This combination therapy may increase the risk of developing renal dysfunction, but the risk can be mitigated by appropriate therapeutic drug monitoring (TDM) and dose adjustments to achieve successful treatment.

Vancomycin in neonatal sepsis: predictive performance of a Chinese neonatal population pharmacokinetic model and clinical efficacy evaluation

BACKGROUND

In the neonatal population, individual calculation and adjustment of vancomycin (VCM) doses has been recommended based on population pharmacokinetics (PPK) methods.

OBJECTIVE

Our previous study established a Chinese neonatal VCM PPK model. The main goal of this study was to evaluate the predictive performance of this PPK model for VCM trough concentration.

METHODS

The data on neonatal severe infection patients treated with VCM were retrospectively collected. The predictive performance of this PPK model was expressed using mean prediction error (MPE), mean absolute prediction error (MAPE), sensitivity and specificity. Linear regression analysis was used to compare predicted and measured VCM concentrations. We drew the receiver operating characteristic (ROC) curve to evaluate the predictive efficacy of the ratio of area under the concentration-time curve over 24 hours to minimum inhibitory concentration (AUC0-24/MIC) and trough concentration for clinical efficacy.

RESULTS

A total of 40 neonates with Gram-positive bacterial sepsis were included. After VCM treatment, 32 (80%) neonates were clinically cured. Eight cases were a clinical failure: the trough concentrations and AUC0-24 were lower than that of the clinical cure patients (8.70±4.30 vs 14.30±4.50 mg/L, p=0.003; 404.30±122.80 vs 515.40±131.70, p=0.037). The measured and predicted trough concentration were 11.16 (5.96, 16.53) mg/L and 10.13 (6.61, 15.73) mg/L, respectively. The MPE and MAPE were 4.62% and 13.26% (5.30%, 25.88%), respectively. The proportion of MAPE <30% in the adjusted regimen was higher than the initial regimen (89.66% vs 65.00%, p=0.039). Predictions of sensitivity and specificity by this PPK model were 88.24% and 94.29%, respectively. The coefficients of determination of linear regression analysis were 0.9171 and 0.9009 for the initial and adjusted regimen, respectively. The AUC0-24 was correlated with the trough concentration (r=0.587, p<0.001). The ROC curve indicated that the optimal cut-off points for predicting clinical efficacy were AUC0-24/MIC >425.47 and trough concentration >9.45 mg/L.

CONCLUSION

This PPK model has good predictive performance in Chinese neonatal patients. Both AUC0-24/MIC and trough concentration can predict the clinical efficacy of antibacterial treatment.

Clinical Practice Guidelines for Therapeutic Drug Monitoring of Vancomycin in the Framework of Model-Informed Precision Dosing: A Consensus Review by the Japanese Society of Chemotherapy and the Japanese Society of Therapeutic Drug Monitoring

Background: To promote model-informed precision dosing (MIPD) for vancomycin (VCM), we developed statements for therapeutic drug monitoring (TDM). Methods: Ten clinical questions were selected. The committee conducted a systematic review and meta-analysis as well as clinical studies to establish recommendations for area under the concentration-time curve (AUC)-guided dosing. Results: AUC-guided dosing tended to more strongly decrease the risk of acute kidney injury (AKI) than trough-guided dosing, and a lower risk of treatment failure was demonstrated for higher AUC/minimum inhibitory concentration (MIC) ratios (cut-off of 400). Higher AUCs (cut-off of 600 μg·h/mL) significantly increased the risk of AKI. Although Bayesian estimation with two-point measurement was recommended, the trough concentration alone may be used in patients with mild infections in whom VCM was administered with q12h. To increase the concentration on days 1–2, the routine use of a loading dose is required. TDM on day 2 before steady state is reached should be considered to optimize the dose in patients with serious infections and a high risk of AKI. Conclusions: These VCM TDM guidelines provide recommendations based on MIPD to increase treatment response while preventing adverse effects.

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.

Using Japanese big data to investigate novel factors and their high-risk combinations that affect vancomycin-induced nephrotoxicity

AIMS

Several factors related to vancomycin-induced nephrotoxicity (VIN) have not yet been clarified. In the present study, we used Japanese big data to investigate novel factors and their high-risk combinations that influence VIN.

METHODS

We employed a large Japanese electronic medical record database and included patients who had been administered intravenous vancomycin between June 2000 and December 2020. VIN was defined as an increase in serum creatinine ≥0.5 mg/dL or 1.5-fold higher than the baseline. The outcomes were: (1) factors affecting VIN that were identified using multiple logistic regression analysis, and (2) combinations of factors that affect the risk of VIN according to a decision tree analysis, which is a typical machine learning method.

RESULTS

Of the 7,306 patients that were enrolled, VIN occurred in 14.2% of them (1,035). A multivariate analysis extracted 22 variables as independent factors. Concomitant ramelteon use (odds ratio; 0.701, 95% confidence interval; 0.512-0.959), ward pharmacy service (0.741, 0.638-0.861), duration of VCM <7 days (0.748, 0.623-0.899) and trough concentrations 10-15 mg/L (0.668, 0.556-0.802) reduce the risk of VIN. Meanwhile, concomitant piperacillin-tazobactam use (2.056, 1.754-2.409) and piperacillin use (2.868, 1.298-6.338) increase the risk. The decision tree analysis showed that a combination of vancomycin trough concentrations ≥20 mg/L and concomitant piperacillin-tazobactam use was associated with the highest risk.

CONCLUSIONS

We revealed that the concomitant ramelteon use and ward pharmacy service may decrease the risk of VIN, while the concomitant use of not only piperacillin-tazobactam but also piperacillin may increase the risk.

The Thirty-Day Mortality Rate and Nephrotoxicity Associated With Trough Serum Vancomycin Concentrations During Treatment of Enterococcal Infections: A Propensity Score Matching Analysis

The objective of this study was to evaluate the relationship between vancomycin trough levels in patients with documented enterococcal infections and mortality, clinical outcomes, microbiological outcomes, and nephrotoxicity. We conducted a retrospective cohort study of patients with enterococcus infections who were prescribed vancomycin with therapeutic drug monitoring during January 2010 and December 2019 at Chiang Mai University Hospital (CMUH). The study enrolled 300 participants who met the inclusion criteria and were prescribed vancomycin with therapeutic drug monitoring. The results of this study showed that, after propensity score matching, a vancomycin trough of ≥15 mg/L was associated with significant differences in 30-days mortality compared to a vancomycin trough of <15 mg/L (aHR: 0.41, 95% CI: 0.21-0.82; p = 0.011). Likewise, a vancomycin trough of ≥15 mg/L was associated with significant differences in the clinical response (aHR: 0.49, 95% CI: 0.26-0.94; p = 0.032), microbiological response (aHR: 0.32, 95% CI: 0.12-0.87; p = 0.025) and nephrotoxicity (aHR: 3.17, 95% CI: 1.39-7.23; p = 0.006), compared with a vancomycin trough of <15 mg/L. However, sub-group analysis found that very high trough levels (>20 mg/L) were also associated with a high rate of nephrotoxicity (aHR: 3.55, 95% CI 1.57-8.07, p = 0.002), when compared with a vancomycin trough of <15 mg/L. The target vancomycin trough concentration was ≥15 mg/L and this target can be an optimal alternative to the use of area under the curve (AUC) values for monitoring the treatment of enterococcal infection.

Clinical Response and Hospital Costs of Therapeutic Drug Monitoring for Vancomycin in Elderly Patients

Cost-effectiveness analysis has been widely used to assess and compare the costs and benefits of a clinical service. The cost-effectiveness of vancomycin therapeutic drug monitoring (TDM) has not been studied in the elderly, who are susceptible to vancomycin-induced adverse effects. This study was performed to evaluate if vancomycin TDM is cost-effective in elderly patients in the Republic of Korea. Using the electronic medical records at a tertiary university hospital, we performed a retrospective observational study to evaluate the cost-effectiveness of vancomycin TDM in 850 elderly patients who underwent vancomycin TDM with an appropriate, recommended dosing regimen and 1094 elderly patients who did not. Cost-effectiveness variables such as clinical outcomes and medical expenses were evaluated using univariate and multivariate analyses. The TDM group spent significantly less than the non-TDM group per patient for total medical expenses (by USD 841.40) and medication expenses (by USD 16.70). However, no significant difference was noted between the TDM and non-TDM groups in clinical outcomes such as microbiological cure, prevention of nephrotoxicity, or reduced mortality, irrespective of admission to the intensive care unit. Vancomycin TDM in elderly patients was associated with economic benefits, but not with better clinical outcomes.

Validation of Vancomycin Area under the Concentration—Time Curve Estimation by the Bayesian Approach Using One-Point Samples for Predicting Clinical Outcomes in Patients with Methicillin-Resistant Staphylococcus aureus Infections

Area under the concentration–time curve (AUC)-guided vancomycin treatment is associated with decreased nephrotoxicity. It is preferable to obtain two samples to estimate the AUC. This study examined the usefulness of AUC estimation via trough concentration (C_min)-only sampling of 260 adults infected with methicillin-resistant Staphylococcus aureus (MRSA) who received vancomycin. The exact C_min sampling time was used for Bayesian estimation. A significantly higher early treatment response was observed in patients with a day 2 AUC ≥ 400 µg·h/mL than those with <400 µg·h/mL, and a significantly higher early nephrotoxicity rate was observed in patients with a day 2 AUC ≥ 600 µg·h/mL than those with <600 µg·h/mL. These AUC cutoff values constituted independent factors for each outcome. In sub-analysis, the discrimination ability for early clinical outcomes using these AUC cutoffs was confirmed only in patients with q12 vancomycin administration. A significant difference in early treatment response using the 400 µg·h/mL cutoff was obtained only in patients with low-risk infections. The usefulness of the vancomycin AUC target to decrease nephrotoxicity while assuring clinical efficacy was even confirmed with a single C_min measurement. However, assessment with two samples might be required in patients with q24 administration or high/moderate-risk MRSA infections.

Development of a decision flowchart to identify the patients need high-dose vancomycin in early phase of treatment

Background

The standard dose of vancomycin (VCM, 2 g/day) sometimes fails to achieve therapeutic concentration in patients with normal renal function. In this study, we aimed to identify factors to predict patients who require high-dose vancomycin (> 2 g/day) to achieve a therapeutic concentration and to develop a decision flowchart to select these patients prior to VCM administration.

Methods

Patients who had an estimated creatinine clearance using the Cockcroft–Gault equation (eCCr) of ≥50 mL/min and received intravenous VCM were divided into 2 cohorts: an estimation set (n = 146, from April to September 2016) and a validation set (n = 126, from October 2016 to March 2017). In each set, patients requiring ≤2 g/day of VCM to maintain the therapeutic trough concentration (10–20 μg/mL) were defined as standard-dose patients, while those who needed > 2 g/day were defined as high-dose patients. Univariate and multivariate logistic regression analysis was performed to identify the predictive factors for high-dose patients and decision tree analysis was performed to develop decision flowchart to identify high-dose patients.

Results

Among the covariates analyzed, age and eCCr were identified as independent predictors for high-dose patients. Further, the decision tree analysis revealed that eCCr (cut off value = 81.3 mL/min) is the top predictive factor and is followed by age (cut off value = 58 years). Based on these findings, a decision flowchart was constructed, in which patients with eCCr ≥81.3 mL/min and age < 58 years were designated as high-dose patients and other patients were designated as standard-dose patients. Subsequently, we applied this decision flowchart to the validation set and obtained good predictive performance (positive and negative predictive values are 77.6 and 84.4%, respectively).

Conclusion

These results suggest that the decision flowchart constructed in this study provides an important contribution for avoiding underdosing of VCM in patients with eCCr of ≥50 mL/min.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40780-021-00231-w.

Index for the appropriate vancomycin dosing in premature neonates and infants

BACKGROUND

In neonates, vancomycin (VCM) is used to treat Gram-positive bacterial infections. However, VCM blood concentrations are affected by gestational age, bodyweight (BW), and renal function. The initial VCM dose adjustment can therefore be difficult, and few reports have evaluated this issue. In this study, we investigated the factors determining the appropriate VCM dosing schedule in neonates, especially premature infants.

METHODS

The VCM dosage and trough concentrations were retrospectively investigated from the initial treatment to maintenance therapy in neonatal intensive care unit patients who underwent therapeutic drug monitoring. We examined the average single-administration VCM dosage during maintenance therapy. We then compared the actual VCM dose with that calculated using an index comprising six items that influence the VCM daily dose (postnatal age, gestational age, BW, serum creatinine level, urine output, and lactate level).

RESULTS

Twenty premature infants were included. The average BW of patients at the initial VCM administration was 975 g. During maintenance therapy, the average VCM dose was 8.4 mg/kg, and the median trough concentration was 12.4 μg/mL. When we applied the six-item index, 18 of 20 patients (90%) had concordant results between the actual VCM dosing schedule and the VCM calculated using the index.

CONCLUSIONS

The average VCM dose and six-item index can facilitate the transition from the initial VCM dose to an appropriate dose in many cases and contribute to early treatment in low-birthweight infants with more variable BW, distribution volumes, and renal function. In conclusion, our six-item index may help standardize VCM administration in premature infants.

Case Report: Monitoring Vancomycin Concentrations and Pharmacokinetic Parameters in Continuous Veno-Venous Hemofiltration Patients to Guide Individualized Dosage Regimens: A Case Analysis

There are limited pharmacokinetic (PK) studies on vancomycin in patients treated with continuous renal replacement therapy (CRRT), and the results have been inconsistent. Because of individual differences, proposing a definite recommendation for the clinical regimen is not possible. Rapidly reaching target vancomycin concentrations will facilitate effective treatment for critically ill patients treated with CRRT. In this study, to understand the dynamic change in drug clearance rates in vivo, analyze the effect of PK changes on drug concentrations, and recommend loading and maintenance dosage regimens, we monitored the blood concentrations of vancomycin and calculated the area under the curve in two critically ill patients treated with vancomycin and continuous veno-venous hemofiltration (CVVH). On the basis of real-time therapeutic drug monitoring results and PK parameters, an individualized vancomycin regimen was developed for patients with CVVH. Good clinical efficacy was achieved, which provided support and reference for empirical vancomycin therapy in these patients.

Clinical evaluation of an authorized medical equipment based on high performance liquid chromatography for measurement of serum voriconazole concentration

BACKGROUND

Therapeutic drug monitoring for voriconazole is recommended for its optimum pharmacotherapy. Although the feedback of the measurement result of serum voriconazole concentration by outsourcing needs a certain time (days within a 1 week), there was no medical equipment for the measurement available in clinical practice. Recently, a medical equipment based on high performance liquid chromatography, named LM1010, has been developed and authorized for clinical use. In this study, to validate the clinical performance of LM1010, we compared the measured serum voriconazole concentrations by LM1010 with those by outsourcing measurement using liquid chromatography-tandem mass spectrometry.

METHODS

We conducted the observational study approved by the institutional review board of Kumamoto University Hospital (No. 1786). Residual serum samples harvested for therapeutic drug monitoring were separated. Measured concentrations by LM1010 by the standard filter method (needs serum volume of > 400 μL) or the dilute method (needs serum volume of 150 μL) were compared with those by outsourcing, respectively. Acceptable measurement error range of 0.72-1.33 was considered. There were 69 serum samples, where the 35 or 34 samples were employed for evaluation of the standard filter method or the dilute method, respectively.

RESULTS

The measured concentration using the standard filter method/outsourcing was 2.22/2.10 μg/mL as the median, 1.57-3.40/1.53-3.62 as the interquartile range, < 0.2-10.76/< 0.2-11.46 μg/mL as the range, while those using the dilute method/outsourcing was 2.36/2.29 μg/mL as the median, 1.08-2.94/1.03-3.06 as the interquartile range, 0.24-10.00/< 0.2-10.85 μg/mL as the range. The regression line for the standard filter method or the dilute method were y = 0.935x + 0.154 or y = 0.933x + 0.162, respectively. The standard filter method or the dilute method showed 11.4% samples (4/35, 95%CI 3.2-26.7%) or 8.8% samples (3/34, 95%CI 1.9-23.7%) out of the acceptable measurement error range, respectively.

CONCLUSION

Measurement of serum voriconazole concentration by LM1010 can be acceptable in clinical TDM practice.

Clinical application of vancomycin population pharmacokinetics model in patients with hematological diseases and neutropenia

To explore the clinical application of a population pharmacokinetics (PPK) model of vancomycin in patients with hematological diseases and neutropenia. Patients with hematological diseases and neutropenia were included in the PPK model study. Nonlinear mixed effect modeling approach (NONMEM) was used for model establishment. Monte Carlo simulation was carried out. A total of 74 patients were divided into model group and non-model group for clinical application research. The model group was given the initial dose of 1g q8h, and the non-model group was given 1g q12h as an empiric initial dosage. The follow-up dose adjustments were made according to the concentration results. This two-compartment model showed good stability and accuracy. The first trough concentration (C0 ) and the compliance rate of the first C0 were much higher in the model group than that in the non-model group (14.30 ± 4.73 μg/ml and 59.38% vs. 8.02 ± 2.61 μg/ml, 35.71%). Less patients needed dose adjustments and fewer adjustment times in the model group than those in the non-model group (12.50% and 0.13 ± 0.34 times vs. 50.00% and 0.61 ± 0.66 times). This suggested that for those patients who had a Creatinine clearance rate (CLCR) ≥ 90 ml/min/1.73 m2 , the initial dose of 1g q8h may help to reach the target C0 (10∼20 μg/ml) quickly. It also helped to reduce the times and number of patients who need dose adjustments. Our PPK model of vancomycin in patients with hematologic diseases and neutropenia can be used to shorten the time to reach the target concentration and reduce the number of dose adjustments.Clinical trial registration: Not applicable (Retrospective study).

Analysis of Risk Factors Associated with Reduced Trough Concentrations of Vancomycin in Relation to Renal Function in a Tertiary Hospital in Japan

BACKGROUND

Low trough concentrations of vancomycin (VCM) are common in patients receiving the drug, because patients are often administered relatively low doses of VCM due to its high potential for renal toxicity. However, the clinical risk factors associated with low VCM trough concentration in relation to renal function are unclear.

METHODS

Patients at our hospital who received VCM intravenously from January 2018 to December 2020 were analyzed. The patients were divided into two groups based on their renal function: normal and lower renal function, such as estimated glomerular filtration rate (eGFR) ≧60 and <60 mL/min/1.73 m2, respectively. In each renal function group, patients' background characteristics, laboratory data and treatments were compared between lower VCM concentration (<10 mg/L) and appropriate VCM concentration (10-20 mg/L) subgroups.

RESULTS

Among 101 patients with normal renal function, 47 and 54 patients, respectively, showed lower and appropriate VCM trough concentrations. Elderly age, short stature, and higher C-reactive protein (CRP) level were significantly more common in the lower VCM concentration group compared with appropriate VCM concentration group. Among the 45 patients with renal dysfunction, 20 and 25 patients, respectively, showed lower and appropriate VCM trough concentrations. CRP levels were significantly higher in lower VCM concentration than appropriate VCM concentration subgroups. Multivariate analysis showed that insufficient total VCM doses and higher CRP might have affected the lower VCM trough concentration in patients with normal renal function.

CONCLUSION

The results of this study suggest that higher CRP might be one of the risk factors associated with lower VCM concentration in both normal and low renal function patients. Severely ill and emergency patients might receive a lower VCM dose due to underestimation of the acceptable VCM dose.

Initial Serum C-reactive Protein Level as a Predictor of Increasing Serum Vancomycin Concentration During Treatment

BACKGROUND

Vancomycin has a narrow therapeutic window, and an increase in its serum concentration-to-dose ratio during treatment can cause renal toxicity. Therefore, this study was aimed at finding a marker to identify patients at risk of increasing serum vancomycin during treatment.

METHODS

This was a retrospective cohort study of patients treated with vancomycin at Kanazawa University Hospital, Japan, from April 2012 to May 2015. Spearman correlation coefficients were calculated to determine the correlations between changes in vancomycin concentration-to-dose ratio and initial values or changes in laboratory data and other parameters. In addition, a multiple regression analysis was conducted.

RESULTS

One hundred ninety-nine patients for whom 2 or more points of data on therapeutic drug monitoring (TDM) of intravenous vancomycin treatment were available and did not undergo dialysis were included in the study. Changes in vancomycin concentration-to-dose ratio were associated with C-reactive protein (CRP) and sodium (Na) levels on the initial day of TDM and with changes in white blood cell count, Na, and estimated glomerular filtration rates (eGFRs). Multiple regression analysis helped identify CRP and Na levels on the initial day of TDM and change in eGFR as independent influencing variables.

CONCLUSIONS

A high serum CRP level on the initial day of TDM is an independent predictor of increasing vancomycin concentration-to-dose ratio in patients receiving intravenous vancomycin treatment, even if eGFR remains unchanged.

A Monocentric Retrospective Study of AUC/MIC Ratio of Vancomycin Associated with Clinical Outcomes and Nephrotoxicity in Patients with Enterococcal Infections

Vancomycin is an antibiotic commonly used for the treatment of enterococcal infections. However, there is no clear correlation regarding of vancomycin area under the curve/minimum inhibitory concentration (AUC/MIC) ratio and clinical outcomes for the treatment of enterococcal infections. The aims of this study were to evaluate the relationship of vancomycin AUC/MIC ratio in patients with clinical outcomes and nephrotoxicity for patients with documented enterococcal infections. A Bayesian technique was used to calculate the average vancomycin AUC_0–24. The MIC was determined using the VITEK 2 automated microbiology system, and the average AUC_0–24/MIC value was calculated for the first 72 h of therapy. All medical records of patients prescribed vancomycin with therapeutic drug monitoring were collected during January 2010–October 2020 at Chiang Mai University Hospital (CMUH). A retrospective single-center cohort of 312 participants were met the inclusion criteria. The results of this study showed that, a vancomycin AUC/MIC of ≥400 mg·h/L was associated with significant differences in clinical response compared to a vancomycin AUC/MIC of <400 mg·h/L (aHR: 0.50, 95% CI: 0.26–0.97; p = 0.042). Likewise, a vancomycin AUC/MIC of ≥400 mg·h/L was associated with significant differences in the microbiological response (aHR: 0.37, 95% CI: 0.14–0.94; p = 0.036), compared to a vancomycin AUC/MIC of <400 mg·h/L. However, nephrotoxicity in patients with a vancomycin AUC/MIC of ≥400 mg·h/L was higher than those with a vancomycin AUC/MIC of <400 mg·h/L (aHR: 3.96, 95% CI: 1.09–14.47; p = 0.037). Declining renal function may be a result of high vancomycin concentrations. In addition, declining renal function (e.g., failure to resolve the focus of infection, co-administration of other antibiotics) might result in higher AUC/MIC. We found a target vancomycin AUC/MIC of ≥400 mg·h/L and this AUC/MIC target value could be optimal for the use for monitoring treatment of enterococcal infections. Thus, vancomycin dosage must be adjusted to achieve the AUC/MIC target and closely monitored for renal function. These findings are not transferable to critically ill patients.

Relationship Between Mean Vancomycin Trough Concentration and Mortality in Critically Ill Patients: A Multicenter Retrospective Study

Background: It remains unclear whether the mean vancomycin trough concentration (VTC) derived from the entire course of therapy is of potential benefit for critically ill patients. This study was conducted to explore the association between mean serum VTC and mortality in intensive care units (ICUs). Methods: 3,603 adult patients with two or more VTC records after receiving vancomycin treatment in the eICU Collaborative Research Database were included in this multicenter retrospective cohort study. Mean VTC was estimated using all measured VTCs and investigated as a continuous and categorical variable. Patients were categorised into four groups according to mean VTC: <10, 10-15, 15-20, and >20 mg/L. Multivariable logistic regression and subgroup analyses were performed to investigate the relationship of mean VTC with mortality. Results: After adjusting for a series of covariates, logistic regression analyses indicated that mean VTC, as a continuous variable, was positively correlated with ICU (odds ratio, 1.038, 95% confidence interval, [1.014-1.063]) and hospital (1.025 [1.005-1.046]) mortalities. As a categorical variable, mean VTC of 10-15 mg/L was not associated with reduced ICU (1.705 [0.975-2.981]) and hospital (1.235 [0.829-1.841]) mortalities. Mean VTC of 15-20 mg/L was not correlated with a lower risk of hospital mortality (1.370 [0.924-2.029]). Moreover, mean VTCs of 15-20 and >20 mg/L were significantly associated with higher ICU mortality (1.924 [1.111-3.332]; 2.428 [1.385-4.258]), and mean VTC of >20 mg/L with higher hospital mortality (1.585 [1.053-2.387]) than mean VTC of <10 mg/L. Similar results were observed in patients with different Acute Physiology and Chronic Health Evaluation IV score, creatinine clearance, age, and body mass index subgroups. Conclusion: Mean VTC was not associated with reduced ICU/hospital related mortality. Our results suggested that VTC monitoring might not guarantee vancomycin efficacy for ICU patients.

Population Pharmacokinetics of Vancomycin Under Continuous Renal Replacement Therapy Using a Polymethylmethacrylate Hemofilter

BACKGROUND

Although continuous hemodiafiltration (CHDF) is often performed in critically ill patients during sepsis treatment, the pharmacokinetics of vancomycin (VCM) during CHDF with a polymethylmethacrylate hemofilter (PMMA-CHDF) have not been revealed. In this study, the authors aimed to describe the population pharmacokinetics of VCM in critically ill patients undergoing PMMA-CHDF and clarify its hemofilter clearance (CLhemofilter).

METHODS

This single-center, retrospective study enrolled patients who underwent intravenous VCM therapy during PMMA-CHDF at the intensive care unit of Chiba University Hospital between 2008 and 2016. A population analysis was performed, and CLhemofilter was assessed.

RESULTS

Twenty-five patients were enrolled. Median body weight (BW) and Sequential Organ Failure Assessment (SOFA) score were 63 kg and 15, respectively. Mean conditions for CHDF were 107.5 ± 18.3 mL/min for blood flow rate and 26.3 ± 6.3 mL/kg/h for effluent flow rate. The mean parameter estimates were distribution volume of the central compartment (V1), 59.1 L; clearance of the central compartment (CL1), 1.35 L/h; distribution volume of the peripheral compartment (V2), 56.1 L; and clearance of the peripheral compartment (CL2), 3.65 L/h. BW and SOFA score were significantly associated with V1 (P < 0.05) and CL1 (P < 0.05), respectively, and were thus selected as covariates in the final model. The estimated dosage of VCM to achieve a target area under the concentration-time curve/minimum inhibitory concentration ≥400 was 27.1 mg/kg for loading and 9.7 mg/kg every 24 hours for maintenance; these dosages were affected by BW and SOFA score. Mean CLhemofilter obtained from 8 patients was 1.35 L/h, which was similar to CL1.

CONCLUSIONS

The authors clarified the pharmacokinetics and CLhemofilter of VCM in PMMA-CHDF patients. The PK of VCM in patients undergoing CHDF appeared to vary not only with the CHDF setting and BW but also with SOFA score.

Evidence-based Guideline for Therapeutic Drug Monitoring of Vancomycin: 2020 Update by the Division of Therapeutic Drug Monitoring, Chinese Pharmacological Society

BACKGROUND

Clinical practice guidelines or recommendations often require timely and regular updating as new evidence emerges, because this can alter the risk-benefit trade-off. The scientific process of developing and updating guidelines accompanied by adequate implementation can improve outcomes. To promote better management of patients receiving vancomycin therapy, we updated the guideline for the therapeutic drug monitoring (TDM) of vancomycin published in 2015.

METHODS

Our updated recommendations complied with standards for developing trustworthy guidelines, including timeliness and rigor of the updating process, as well as the use of the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. We also followed the methodology handbook published by the National Institute for Health and Clinical Excellence and the Spanish National Health System.

RESULTS

We partially updated the 2015 guideline. Apart from adults, the updated guideline also focuses on pediatric patients and neonates requiring intravenous vancomycin therapy. The guideline recommendations involve a broadened range of patients requiring TDM, modified index of TDM (both 24-hour area under the curve and trough concentration), addition regarding the necessity and timing of repeated TDM, and initial dose for specific subpopulations. Overall, 1 recommendation was deleted and 3 recommendations were modified. Eleven new recommendations were added, and no recommendation was made for 2 clinical questions.

CONCLUSIONS

We updated an evidence-based guideline regarding the TDM of vancomycin using a rigorous and multidisciplinary approach. The updated guideline provides more comprehensive recommendations to inform rational and optimized vancomycin use and is thus of greater applicability.

An evaluation on the association of vancomycin trough concentration with mortality in critically ill patients: A multicenter retrospective study

To determine the impact of initial vancomycin trough concentration (VTC) on mortality in adult patients in the intensive care unit (ICU) undergoing vancomycin therapy. During their first ICU stay, patients with initial VTC records after vancomycin treatment were recruited from the eICU Collaborative Research Database to this multicenter retrospective cohort study, and classified into four groups according to VTC: less than 10, 10–15, 15–20, and greater than 20 mg/L. Multivariable logistic regression and sensitivity analyses were performed to explore the association of VTC, as a continuous and categorical variable, with mortality. This study enrolled 7220 patients from 335 different ICUs at 208 hospitals. Multivariable logistic regression models indicated that VTC was positively correlated with ICU (odds ratio [OR], 1.028, 95% confidence interval [CI], 1.019–1.037) and hospital (OR 1.028, 95% CI, 1.020–1.036) mortalities. Moreover, compared with VTC less than 10 mg/L, VTCs of 10–15, 15–20, and greater than 20 mg/L were associated with a higher risk of ICU mortality (OR, 1.330, 95% CI, 1.070–1.653; OR, 1.596, 95% CI, 1.265–2.015; abd OR, 1.875, 95% CI, 1.491–2.357, respectively), and VTCs of 15–20 and greater than 20 mg/L were also correlated with increased hospital mortality (OR, 1.482, 95% CI, 1.225–1.793; and OR, 1.831, 95% CI, 1.517–2.210, respectively). Similar results persisted in patients with different Acute Physiology and Chronic Health Evaluation Ⅳ scores, creatinine clearance levels, ages, and body mass indexes. Our findings indicated a potential relationship of initial VTC with ICU and hospital mortalities in patients in the ICU. However, due to the retrospective nature of this study, future prospective studies or randomized controlled trials are needed to validate those results.

Performance of Area under the Concentration-Time Curve Estimations of Vancomycin with Limited Sampling by a Newly Developed Web Application

PURPOSE

Therapeutic drug monitoring guided by the area under the concentration-time curve (AUC-guided TDM) is recommended for vancomycin. However, validated efficient software remains elusive to popularize AUC-guided TDM in Japan. The aim of this study was to validate a newly developed web application, PAT, for AUC estimation.

METHODS

PAT was developed on the R ver. 3.6.2 platform for use with mobile phones and personal computers. AUC estimated by PAT (AUC_PAT) was evaluated against the reference AUC (AUC_REF) calculated with the log-linear trapezoidal rule using eight measured concentrations, or against AUC (AUC_BM-P) calculated using an evaluated available software with clinical data.

RESULTS

Investigating the best sampling points with limited sampling, PAT produced the least bias using two concentrations at 1 h and 11 h after the end of infusion (slope 1.18, intercept -15.57, median AUC_PAT/AUC_REF 0.93 [range 0.81-1.24]), where only one estimation (6%) was out of the predetermined acceptable range of 0.8-1.2. Employment of only a trough concentration was more biased (AUC_PAT/AUC_REF range 0.73-1.30 for 11 h, AUC_PAT/AUC_REF range 0.62-1.40 for 23 h). In comparison with the evaluated software, AUC_PAT was not biased against the AUC_BM-P (slope 1.04, intercept -15.80, median AUC_PAT/AUC_BM-P 1.00 [range 0.86-1.10]).

CONCLUSIONS

The new application using two concentrations was appropriately validated and might be efficient in popularizing the AUC-guided TDM of vancomycin.

[Assessment of Renal Function and Simulation Using Serum Cystatin-C in an Elderly Patient with Uncontrollable Plasma Vancomycin Levels Due to Muscular Dystrophy: A Case Report]

Herein, we describe a case of an elderly patient with muscular dystrophy for whom control of the plasma vancomycin (VCM) concentration proved difficult when he developed a catheter-related bloodstream infection. The pharmacist initially carried out therapeutic drug monitoring using an estimate of the creatinine clearance (CL_cr) level, which was based on the serum creatinine (SCr) and serum cystatin-C (CysC) levels, but was ultimately unable to control the plasma VCM concentration. Therefore, the plasma VCM concentration was predicted ex post facto using population pharmacokinetic parameters as a covariate; that is, directly including the glomerular filtration rate (GFR_CysC) estimated from the CysC level, which is not affected by the muscle mass. As a result, the estimated VCM concentration was closer to the actual concentration than that predicted using CL_cr. Furthermore, the results of examining the predictive accuracy according to the assessment of renal function at the time of initial VCM administration suggested that estimation of the trough concentration using GFR_CysC might be useful in elderly patients with muscular dystrophy.