Adequacy of a Vancomycin Dosing Regimen in Patients Receiving High-Flux Hemodialysis

Vancomycin Dosing in Patients on Intermittent Hemodialysis-A Retrospective Study

PURPOSE

To determine the incidence of therapeutic target attainment using a three-times per week protocol for vancomycin therapy given during the last hour of intermittent hemodialysis (HD).

METHODS

A single-center retrospective cohort study was conducted of patient medical records in a remote dialysis center from January 2017 to July 2023. Adult patients with chronic kidney disease stage 5 on ≥3 months of intermittent HD who had received a course of vancomycin therapy with ≥1 serum vancomycin concentration recorded were included. Demographic and dosing data were collected. Clinician adherence with the dosing protocol and attainment of the therapeutic target (trough concentration within 15-20 mg/L) following the loading and maintenance doses were assessed. Factors associated with target nonattainment following the loading dose were analyzed, and the 48- and 72-h maintenance dosing intervals were analyzed for target nonattainment.

FINDINGS

A total of 98 vancomycin courses (67 patients) were available for analysis. Only 38% of the loading doses were prescribed as per protocol. Following the loading dose, 25% of trough concentrations achieved the therapeutic target concentration (15-20 mg/L), 25% returned a supra-therapeutic concentration (>20 mg/L) and 50% were sub-therapeutic (<15 mg/L). When compared with those achieving target, sub-therapeutic concentrations were associated with a lower loading dose (median 16.6 vs 20.0 mg/kg, P < 0.002), and supra-therapeutic concentrations had a shorter dosing interval between the loading dose and first maintenance dose (median 31.5 vs 39.0 h, P = 0.06). Of the 201 maintenance trough concentrations collected, 65% were therapeutic, 21% were sub-therapeutic and 14% were supra-therapeutic, with an overall median trough concentration of 17.3 mg/L. As the treatment duration increased, an increase was seen in the number of dose adjustments required to achieve the target trough concentration. The 48-h dosing interval was associated with more supra-therapeutic concentrations and the 72-h interval was associated with more sub-therapeutic concentrations (df = 2, P = 0.022).

IMPLICATIONS

We have identified a high rate of target nonattainment for HD patients on a three times a week vancomycin dosing regimen. We recommend a loading dose of 20 to 25 mg/kg irrespective of the indication and a better-defined dosing interval after the loading dose. A higher maintenance dose should be prescribed when the time to next dialysis session is 72 h. Further pharmacokinetic studies are needed to assess factors influencing target concentration attainment following the maintenance doses and to determine an optimal dosing regimen.

Do medical devices contribute to sustainability? The role of innovative polymers and device design

Sustainability of a medical device has not yet become a major issue in public discussions compared to other topics with impact to material performance, clinical application, production economy and environmental pollution. Due to their unique properties, polymers (plastics) allow for multiple, flexible applications in medical device technology. Polymers are part of the majority of disposable and single use medical device and contribute with 3% to the worldwide production of plastics. The global medical polymer market size was valued 19.9 billion US-$ in 2022 and its value projection for 2023 is expected to reach 43.03 billion US-$ Here, a wider concept of related sustainability is introduced for medical devices and their polymer components. A close look on medical device specification reveals that additional properties are required to provide sustainability, such as biodegradability, quality by device design (QbD), as well as an inbuild performance service for patients, healthcare professionals and healthcare providers. The increasing global numbers for chronic and non-communicable diseases require a huge demand for single use medical devices. A careful look at polymer specification and its performance properties is needed, including possible chemical modifications and degradation processes during waste disposal. Bioengineers in charge of design and production of medical devices will only be successful when they apply a holistic and interdisciplinary approach to medical device sustainability.

Vancomycin and daptomycin dosing recommendations in patients receiving home hemodialysis using Monte Carlo simulation

BACKGROUND

Few drug dosing recommendations for patients receiving home hemodialysis (HHD) have been published which has hindered the adoption of HHD. HHD regimens vary widely and differ considerably from conventional, thrice weekly, in-center hemodialysis in terms of treatment frequency, duration and blood and dialysate flow rates. Consequently, vancomycin and daptomycin clearances in HHD are also likely to be different, consequently HHD dosing regimens must be developed to ensure efficacy and minimize toxicity when these antibiotics are used. Many HHD regimens are used clinically, this study modeled ten common HHD regimens and determined optimal vancomycin and daptomycin dosing for each HHD regimen.

METHODS

Monte Carlo simulations using pharmacokinetic data derived from the literature and demographic data from a large HHD program treating patients with end stage kidney disease were incorporated into a one-compartment pharmacokinetic model. Virtual vancomycin and daptomycin doses were administered post-HHD and drug exposures were determined in 5,000 virtual patients receiving ten different HHD regimens. Serum concentration monitoring with subsequent dose changes was incorporated into the vancomycin models. Pharmacodynamic target attainment rates were determined for each studied dose. The lowest possible doses that met predefined targets in virtual patients were chosen as optimal doses.

RESULTS

HHD frequency, total dialysate volumes and HHD durations influenced drug exposure and led to different dosing regimens to meet targets. Antibiotic dosing regimens were identified that could meet targets for 3- and 7-h HHD regimens occurring every other day or 4-5 days/week. HHD regimens with 3-day interdialytic periods required higher doses prior to the 3-day period. The addition of vancomycin serum concentration monitoring allowed for calculation of necessary dosing changes which increased the number of virtual subjects meeting pharmacodynamic targets.

CONCLUSIONS

Doses of vancomycin and daptomycin that will meet desired pharmacodynamic targets in HHD are dependent on patient and HHD-specific factors. Doses used in conventional thrice weekly hemodialysis are unlikely to meet treatment goals. The antibiotic regimens paired with the HHD parameters studied in this analysis are likely to meet goals but require clinical validation.

Practices, Knowledge, and Attitudes of Nephrologists Towards Prescribing and Monitoring Vancomycin at Dialysis Centers

BACKGROUND

Vancomycin dosing protocols are varied in the literature for hemodialysis patients. This study sought to determine nephrologists' practices, knowledge, attitudes, and barriers toward prescribing and monitoring vancomycin at dialysis centers.

METHODS

A cross-sectional and multi-center study was conducted in Kuwait using a validated self-administered questionnaire among 168 nephrologists. Descriptive and comparative analyses were performed using SPSS (version 28).

RESULTS

The response rate was 75% (n = 126). Over half of nephrologists frequently prescribed a vancomycin loading dose of 1000 mg (53.2%) and a maintenance dose of 500 mg (51.6%) to all patients. Their overall median (IQR) percentage knowledge about the therapeutic monitoring of vancomycin was 66.7% (33.3) and was found to be higher in nephrologists aged ≤ 40 years and in registrars/senior registrars (p < 0.05). Their overall median (IQR) attitude score was 4.0 (1.0) [positive attitude]. Nephrologists with > 15 years of practice experience expressed higher attitudes (p < 0.05). The top two perceived barriers were a lack of clear local hospital/national guidelines (60.3%) for vancomycin dosing in dialysis and inconsistencies among different dosing references and guidelines (51.6%).

CONCLUSION

Findings showed that nephrologists have varying practices, moderate knowledge, and positive attitudes toward prescribing and monitoring vancomycin and highlight the need for interventions to overcome the perceived barriers.

An updated vancomycin dosing protocol for initiating therapy in patients undergoing intermittent high-flux hemodialysis

DISCLAIMER

In an effort to expedite the publication of articles, AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

To design an updated vancomycin dosing protocol for initiating therapy in patients undergoing chronic intermittent high-flux hemodialysis (iHFHD) that is congruent with the revised 2020 consensus guidelines for therapeutic drug monitoring (TDM).

METHODS

Monte Carlo simulation methods were used to study vancomycin dosing for patients on iHFHD. Vancomycin regimens were constructed as intravenous infusions (for intradialytic administration) of a loading dose and maintenance doses 3 times weekly during subsequent dialysis sessions. Vancomycin plasma concentrations were simulated, and the probability of target attainment (PTA) for a 24-hour area under the time-concentration curve (AUC24) of 400 to 700 mg • h/L was determined. Standardized weight-based (ie, dose-banding) regimens were investigated, and an optimized protocol was selected based on TDM target attainment and practical considerations for use in the dialysis setting.

RESULTS

The proposed vancomycin dosing protocol (for intradialytic administration) specifies 3 regimens: (1) a 1,500-mg loading dose and 750-mg maintenance doses for patients weighing 50 kg to 69 kg; (2) a 2,000-mg loading dose and 1,000-mg maintenance doses for patients weighing 70 kg to 89 kg; and (3) a 2,500-mg loading dose and 1,250-mg maintenance doses for patients weighing 90 kg to 110 kg. In a simulated hemodialysis population (n = 1,000), the proposed protocol delivered median (interquartile range [IQR]) loading and maintenance doses of 25.0 (23.4-26.6) mg/kg and 12.5 (11.8-13.3) mg/kg, respectively. The PTA for an AUC24 of 400 to 700 mg • h/L was 74.7% on day 1 and 70.8% on day 8, with less than 10% of values exceeding the target range.

CONCLUSION

Our proposed dosing protocol for patients undergoing iHFHD offers an updated and practical approach for initiating vancomycin therapy that can be optimized with early TDM.

Comparison of antimicrobial dosing recommendations in patients receiving intermittent hemodialysis among drug information resources

WHAT IS KNOWN AND OBJECTIVE

Tertiary drug information resources are frequently consulted for the optimal antimicrobial dosing in intermittent hemodialysis (IHD) patients. Yet, significant discrepancy may exist in dosing recommendations between resources. This study was to evaluate the consistency of antimicrobial dosing recommendations in IHD among four different drug information resources and the relevance of referenced pharmacokinetic studies.

METHODS

Dosing recommendations of 29 commonly prescribed antimicrobials in IHD patients were collected from Micromedex, LexiComp, Clinical Pharmacology and Drug Prescribing in Renal Impairment to compare dosing categorization and the total daily dose (TDD). Significant dosing discrepancies were defined as ≥30% difference. Referenced pharmacokinetic studies were evaluated for their relevance in current practice, using sample size, hemodialyzer types, the use of optimal pharmacodynamic targets and the consideration of different interdialytic dosing periods.

RESULTS AND DISCUSSION

A significant variation was found both in dosing categorization and recommended doses between resources. Seventeen drugs were compared for TDD with significant dosing discrepancy in 8 drugs. Among 42 referenced pharmacokinetic studies, 40 were evaluated. Mean patient numbers of pharmacokinetic studies were 13 ranging from 3 to 70. Sixty per cent of studies utilized contemporary hemodialyzers (e.g., high-flux and/or high efficiency). The optimal pharmacodynamic targets and the impact of different interdialytic intervals were assessed only in 27.5% and 7.5% respectively.

WHAT IS NEW AND CONCLUSION

Inconsistent antimicrobial dosing recommendations for IHD patients exist among four well-established resources. Many referenced pharmacokinetic studies utilized outdated or less pharmacodynamically relevant study methods. Newer studies are warranted to reflect contemporary dialysis practice and assess its impact on optimal antimicrobial dosing.

Pharmacokinetics of Vancomycin in Pediatric Patients Receiving Intermittent Hemodialysis or Hemodiafiltration

INTRODUCTION

Vancomycin is a common antibiotic used to treat hemodialysis (HD) or hemodiafiltration (HDF)-related infections in pediatric patients, but optimal dosing remains unknown. This is the first observational study to characterize the pharmacokinetics and evaluate dosing of vancomycin in this population.

METHODS

Eligible patients received IV vancomycin 10 mg/kg per dose postdialysis followed by a series of serum vancomycin concentrations collected before, immediately after, 1 hour after, and 4 hours after dialysis. The pharmacokinetic parameters were estimated using 1- and 2-compartment models and a nonlinear least-squares algorithm.

RESULTS

Among 42 vancomycin courses in 16 patients, 1 compartment model had the best fit for observed data. The net drug removal was 43 ± 13% (39% for HD and 50% for HDF) from an average 3-hour HD/HDF session. The mean elimination constant was 0.28 h-1 (standard deviation [SD], 0.11 h-1) during the intradialytic period compared with 0.0049 h-1 (SD, 0.004 h-1) when off dialysis. The mean volume of distribution was 0.65 (SD, 0.19) L/kg. Duration of dialysis session and mode of dialysis (HD vs. HDF) were significant predictors of vancomycin pharmacokinetic parameters. Half-life was shorter for HDF compared with HD (2.1 vs. 3.5 hours).

CONCLUSIONS

Based on the simulations, an initial vancomycin dose of 10 mg/kg per dose and redosing postdialysis was optimal to achieve a vancomycin concentration range of 5 to 12 mg/L at 4 hours postdialysis and 24-hour area under the curve over minimum inhibitory concentration of ≥400 hours. Therapeutic drug monitoring is necessary to account for residual variability in vancomycin elimination in pediatric patients receiving HD/HDF.

Post-Dialysis Parenteral Antimicrobial Therapy in Patients Receiving Intermittent High-Flux Hemodialysis

Patients with end-stage renal disease (ESRD) requiring intermittent hemodialysis (IHD) are at increased risk of infection, which represents a leading cause of mortality in this population. The use of additional vascular access devices such as peripherally inserted central catheters to treat such infections should be minimized in patients with ESRD requiring IHD in order to mitigate complications such as infection and thrombosis and to maintain venous patency for hemodialysis access. Intravenous antimicrobial dosing following IHD has the advantages of avoiding additional access devices and providing convenience for patients and providers. Vancomycin, cefazolin, and aminoglycosides have historically been regarded as the primary intravenous antimicrobials administered with IHD given their relatively low cost, convenient dosing, and longevity of clinical use. Despite this, a growing body of literature is evaluating the use of an expanded list of antimicrobials that may be employed using post-dialysis dosing for patients requiring IHD; however, the available data are largely limited to pharmacokinetic studies and small cohorts of infected patients or uninfected subjects. Post-dialytic dosing of intravenous antimicrobials may be considered on a patient-by-patient basis after careful consideration of clinical, microbiological, and logistical factors that may influence the probability of treatment success. This document reviews and evaluates currently available information on the post-dialytic administration of an expanded list of intravenous antimicrobials in the setting of thrice-weekly, high-flux IHD.

Pharmacokinetics of Vancomycin in Critically Ill Patients Undergoing Sustained Low-Efficiency Dialysis

INTRODUCTION

Vancomycin pharmacokinetic data in critically ill patients receiving sustained low-efficiency dialysis (SLED) is limited. Published data using vancomycin with intermittent hemodialysis and continuous renal replacement therapy may not be applicable to hybrid dialysis modalities such as SLED. Current drug references lack recommendations for vancomycin dosing in patients receiving SLED.

OBJECTIVE

The objective of this study was to determine vancomycin pharmacokinetics during SLED.

METHODS

A total of 20 patients who were critically ill with oliguric or anuric renal failure who received vancomycin and SLED were included in the study. Surrounding one SLED session, serum vancomycin blood samples were drawn before the initiation of SLED, at the termination of SLED, and 4 hours after completion of SLED treatment. Following this, patients received vancomycin, dosed to target a goal peak of 20-30 mcg/ml. A vancomycin peak level was drawn 1 hour after the end of the infusion. SLED treatment duration was at least 7 hours. Continuous data are reported as median (interquartile range) and categorical data as percentage.

RESULTS

The vancomycin elimination rate and half-life were 0.051 hours (0.042-0.074 hours) and 13.6 hours (9.4-16.6 hours), respectively. SLED reduced vancomycin serum concentrations by 35.4% (31.5-43.8%), and vancomycin rebound was 9.8% (2.5-13.7%). The vancomycin dose administered post-SLED was 1000 mg (875-1125 mg). For 18 patients, the patient-specific volume of distribution was 0.88 L/kg (0.67-1.1 L/kg), vancomycin clearance was 3.5 L/hr (2.2-5.2 L/hr), and the area under the concentration-time curve during the study time period was 280.8 mg·hr/L (254.7-297.3 mg·hr/L).

CONCLUSION

Vancomycin is significantly removed during SLED with little rebound in serum concentrations 4 hours after completion of SLED. Based on study findings, patients who are critically ill require additional vancomycin dosing after each SLED session to maintain therapeutic post-SLED vancomycin concentrations. Therapeutic drug monitoring of vancomycin is recommended during SLED.

Vancomycin for Dialytic Therapy in Critically Ill Patients: Analysis of Its Reduction and the Factors Associated with Subtherapeutic Concentrations

This study aimed to evaluate the reduction in vancomycin through intermittent haemodialysis (IHD) and prolonged haemodialysis (PHD) in acute kidney injury (AKI) patients with sepsis and to identify the variables associated with subtherapeutic concentrations. A prospective study was performed in patients admitted at an intensive care unit (ICU) of a Brazilian hospital. Blood samples were collected at the start of dialytic therapy, after 2 and 4 h of treatment and at the end of therapy to determine the serum concentration of vancomycin and thus perform pharmacokinetic evaluation and PK/PD modelling. Twenty-seven patients treated with IHD, 17 treated with PHD for 6 h and 11 treated with PHD for 10 h were included. The reduction in serum concentrations of vancomycin after 2 h of therapy was 26.65 ± 12.64% and at the end of dialysis was 45.78 ± 12.79%, higher in the 10-h PHD group, 57.70% (40, 48–64, 30%) (p = 0.037). The ratio of the area under the curve to minimal inhibitory concentration (AUC/MIC) at 24 h in the PHD group was significantly smaller than at 10 h (p = 0.047). In the logistic regression, PHD was a risk factor for an AUC/MIC ratio less than 400 (OR = 11.59, p = 0.033), while a higher serum concentration of vancomycin at T0 was a protective factor (OR = 0.791, p = 0.009). In conclusion, subtherapeutic concentrations of vancomycin in acute kidney injury (AKI) patients in dialysis were elevated and may be related to a higher risk of bacterial resistance and mortality, besides pointing out the necessity of additional doses of vancomycin during dialytic therapy, mainly in PHD.

Evaluation and Development of Vancomycin Dosing Schemes to Meet New AUC/MIC Targets in Intermittent Hemodialysis Using Monte Carlo Simulation Techniques

Published vancomycin dosing recommendations for patients receiving maintenance hemodialysis were not designed to meet newly recommended 24-hour area under the curve/minimum inhibitory concentration (AUC_24h /MIC) pharmacokinetic/pharmacodynamic targets. The aims of this study were to predict pharmacokinetic/pharmacodynamic target attainment rates with a commonly used vancomycin regimen and to design a new dosing scheme incorporating therapeutic drug monitoring (TDM) to maximize target attainment in patients receiving vancomycin and hemodialysis with high- or low-flux hemodialyzers. Vancomycin pharmacokinetic- and dialysis-specific parameters were incorporated into Monte Carlo simulations (MCS). A commonly used vancomycin regimen was modeled to determine its likelihood of attaining AUC_24h /MIC targets for 1 week of thrice-weekly hemodialysis treatments. MCS was then used to develop optimal initial vancomycin dosing for patients receiving intradialytic or postdialytic vancomycin administration with either high- or low-flux hemodialyzers. Finally, a new MCS model incorporating TDM was built to further optimize the probability of pharmacokinetic/pharmacodynamic target attainment. Traditional vancomycin dosing methods are unlikely to meet AUC_24h /MIC targets. Vancomycin doses necessary to attain AUC_24h /MIC targets are significantly influenced by hemodialyzer permeability and whether vancomycin is administered intradialytically or after hemodialysis. Depending on dialyzer type and whether vancomycin is administered during or after hemodialysis, loading doses of 25 to 35 mg/kg followed by maintenance doses of 7.5 to 15 mg/kg are necessary to reach minimum AUC_24h /MIC targets in 90% of virtual patients. For a 3-day interdialytic period, a 30% higher maintenance dose is required to maintain target attainment. Dosing based on a single vancomycin serum concentration obtained prior to the second dialysis session greatly enhances the probability of target attainment.

In vivo evaluation of drug dialyzability in a rat model of hemodialysis

It is important to calculate the drug removal by hemodialysis (HD) for drug dosing regimens in HD patients. However, there are limited and inconsistent information about the dialyzability of drugs by HD. Therefore, the aim of our study is to evaluate drug removal by utilizing a rat model of HD (HD rat) and to extrapolate this result to the drug removal rate in HD patients. HD rats received bilateral nephrectomy and HD for 2 h. The dialysis removal of 6 drugs was evaluated in HD rats. Dialysis efficiency, plasma protein binding rate (PBR) and distribution volume (Vd) of drugs were also measured. Furthermore, we examined the correlation between the dialyzability of drug in HD rats and humans and constructed the prediction formula of the drug dialyzability in HD patients. The clearance of urea and creatinine and normalized dialysis dose in HD rats were 0.83 ± 0.07 mL/min, 0.70 ± 0.08 mL/min, and 0.13 ± 0.06, respectively. The drug dialyzability in HD rats was similar to reported clinical data except for doripenem. A higher correlation was observed between drug dialyzability in reported clinical data and HD rats which were adjusted for PBR (r² = 0.936; p < 0.001) compared to unadjusted (r² = 0.812; p = 0.009). Therefore, we constructed the prediction formula of the drug dialyzability in HD patients by utilizing the HD rat model and PBR. This study is useful for evaluating the dialyzability of high-risk drugs in a clinical setting and might provide appropriate preclinical dialyzability data for new drug.

Validation of a Weight Threshold-Based Vancomycin Dosing Protocol for Patients Undergoing Intermittent Hemodialysis

BACKGROUND

Patients receiving intermittent hemodialysis (IHD) are at high risk of acquiring gram-positive infections, which are often treated with IV vancomycin. Despite frequent use of vancomycin in the IHD setting, there is variability in dosing and monitoring practices among clinicians at the study institution. There is also a paucity of evidence regarding optimal vancomycin dosing to achieve target pre-IHD serum concentration.

OBJECTIVES

The primary objective was to compare the percentage of treatment courses with a serum vancomycin concentration between 15 and 20 mg/L, measured before the third IHD session, before and after implementation of a weight threshold-based dosing protocol. The secondary objectives were to compare the percentage of treatment courses with a pre-third IHD vancomycin concentration between 10 and 22 mg/L and the number of vancomycin measurements per treatment day, before and after protocol implementation.

METHODS

This quasi-experimental, single-centre study included inpatients and outpatients who underwent IHD and received at least 2 IV doses of vancomycin, with vancomycin being measured in an appropriately drawn sample before the third IHD session. Before protocol implementation, vancomycin dosing was at the clinician's discretion (usual care). After protocol implementation, each patient received a loading dose of 1000, 1500, or 2000 mg and a maintenance dose of 500, 750, or 1000 mg, depending on body weight.

RESULTS

The percentage of treatment courses with a pre-third IHD vancomycin concentration between 15 and 20 mg/L was greater after implementation of the protocol than with usual care, but the difference was nonsignificant (44% [8/18] versus 20% [3/15], p = 0.27). However, the percentage of treatment courses with a pre-third IHD vancomycin concentration between 10 and 22 mg/L was significantly higher after protocol implementation (94% [17/18] versus 53% [8/15], p = 0.012). There was no difference in the median number of vancomycin measurements per treatment day before and after protocol implementation (0.133 versus 0.125, p = 0.99).

CONCLUSIONS

At the study institution, the likelihood of achieving recommended vancomycin concentration increased (relative to previous practice) after implementation of a simplified vancomycin dosing protocol for patients undergoing IHD.

Antibiotic Dosing for Critically Ill Adult Patients Receiving Intermittent Hemodialysis, Prolonged Intermittent Renal Replacement Therapy, and Continuous Renal Replacement Therapy: An Update

Objective: To summarize current antibiotic dosing recommendations in critically ill patients receiving intermittent hemodialysis (IHD), prolonged intermittent renal replacement therapy (PIRRT), and continuous renal replacement therapy (CRRT), including considerations for individualizing therapy. Data Sources: A literature search of PubMed from January 2008 to May 2019 was performed to identify English-language literature in which dosing recommendations were proposed for antibiotics commonly used in critically ill patients receiving IHD, PIRRT, or CRRT. Study Selection and Data Extraction: All pertinent reviews, selected studies, and references were evaluated to ensure appropriateness for inclusion. Data Synthesis: Updated empirical dosing considerations are proposed for antibiotics in critically ill patients receiving IHD, PIRRT, and CRRT with recommendations for individualizing therapy. Relevance to Patient Care and Clinical Practice: This review defines principles for assessing renal function, identifies RRT system properties affecting drug clearance and drug properties affecting clearance during RRT, outlines pharmacokinetic and pharmacodynamic dosing considerations, reviews pertinent updates in the literature, develops updated empirical dosing recommendations, and highlights important factors for individualizing therapy in critically ill patients. Conclusions: Appropriate antimicrobial selection and dosing are vital to improve clinical outcomes. Dosing recommendations should be applied cautiously with efforts to consider local epidemiology and resistance patterns, antibiotic dosing and infusion strategies, renal replacement modalities, patient-specific considerations, severity of illness, residual renal function, comorbidities, and patient response to therapy. Recommendations provided herein are intended to serve as a guide in developing and revising therapy plans individualized to meet a patient's needs.

A Guide to Understanding Antimicrobial Drug Dosing in Critically Ill Patients on Renal Replacement Therapy

A careful management of antimicrobials is essential in the critically ill with acute kidney injury, especially if renal replacement therapy is required. Acute kidney injury may lead per se to clinically significant modifications of drugs' pharmacokinetic parameters, and the need for renal replacement therapy represents a further variable that should be considered to avoid inappropriate antimicrobial therapy. The most important pharmacokinetic parameters, useful to determine the significance of extracorporeal removal of a given drug, are molecular weight, protein binding, and distribution volume. In many cases, the extracorporeal removal of antimicrobials can be relevant, with a consistent risk of underdosing-related treatment failure and/or potential onset of bacterial resistance. It should also be taken into account that renal replacement therapies are often not standardized in critically ill patients, and their impact on plasma drug concentrations may substantially vary in relation to membrane characteristics, treatment modality, and delivered dialysis dose. Thus, in this clinical scenario, the knowledge of the pharmacokinetic and pharmacodynamic properties of different antimicrobial classes is crucial to tailor maintenance dose and/or time interval according to clinical needs. Finally, especially for antimicrobials known for a tight therapeutic range, therapeutic drug monitoring is strongly suggested to guide dosing adjustment in complex clinical settings, such as septic patients with acute kidney injury undergoing renal replacement therapy.

The ratio of pre-dialysis vancomycin trough serum concentration to minimum inhibitory concentration is associated with treatment outcomes in methicillin-resistant Staphylococcus aureus bacteremia

Background

Vancomycin is a standard treatment for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, and its efficacy is closely linked to the recommended serum trough concentration of 15–20 mg/L. However, it is unknown how the pre-dialysis trough serum concentration (C_pre-HD) correlates with MRSA eradication in renal failure patients undergoing intermittent hemodialysis (HD).

Objective

To evaluate the relationship between C_pre-HD and the treatment outcomes in this population.

Materials and methods

A retrospective study was conducted to enroll renal failure patients undergoing HD who had received vancomycin treatment for MRSA bacteremia during January 2013 to June 2016. Treatment failure was defined as persistent bacteremia after ≥ 7 days of vancomycin therapy or recurrent MRSA infection within 30 days. Patient characteristics, vancomycin dosing regimen, C_pre-HD, vancomycin minimum inhibitory concentration (MIC), and subsequent culture data were reviewed. The receiver operating characteristic (ROC) curve was used to find the optimal cut-off point of C_pre-HD.

Results

42 patients were enrolled and 64% had treatment failure. Although there were no significant differences in demographics or C_pre-HD between the two groups, C_pre-HD/MIC was significantly higher in the success group than that in the failure group (22.80±10.90 vs. 14.94±6.11, p = 0.019). The area under the ROC curve was 0.74, while the sensitivity, specificity, positive predictive value, and negative predictive value were 67%, 78%, 62.5%, and 81%, respectively, at the optimal C_pre-HD/MIC of ≧ 18.6.

Conclusions

C_pre-HD/MIC was associated with vancomycin treatment outcome in MRSA bacteremia, and targeting to achieve a C_pre-HD/MIC of ≧ 18.6 may improve treatment outcomes in renal failure patients who are on intermittent HD.

Vancomycin dosing in chronic high-flux haemodialysis: a systematic review

The aim of this study was to systematically evaluate whether non-weight-based dosing (non-WBD) or weight-based dosing (WBD) of vancomycin leads to a higher proportion of patients achieving the pharmacokinetic/pharmacodynamic target. Studies from January 1985 to February 2017 were identified through Cochrane, MEDLINE and Embase databases. Those conducted in adults with end-stage renal disease receiving high-flux haemodialysis (HD) and intravenous vancomycin were included. The primary outcome was the proportion of patients with a pre-HD vancomycin concentration of 15-20 mg/L and/or an area under the concentration-time curve/minimum inhibitory concentration (AUC/MIC) ratio ≥400. Of the 3948 studies screened, 5 met the inclusion criteria. The proportion of patients with pre-HD concentrations between 15-20 mg/L were 35% (non-WBD) and 13% (WBD) post-loading dose. During maintenance dosing, the proportion of patients with pre-HD concentrations between 15-20 mg/L were 37% (non-WBD) and 50-67% (WBD). The proportion of pre-HD concentrations <15 mg/L was greater in the non-WBD group post-loading dose but was similar between the non-WBD and WBD group during maintenance dosing. One study reported that all patients had an AUC/MIC ≥ 400 for micro-organisms with an MIC ≤ 1 mg/L for weight-based maintenance dosing. The limited data suggest that WBD may be preferential as there was a smaller proportion of pre-HD concentrations falling below 15 mg/L. However, larger well-designed studies of higher quality are required to provide guidance for vancomycin dosing in the high-flux HD setting. Future research should focus on reporting AUC/MIC ratios and exploring clinical outcomes in this patient population.

Optimization of anti-infective dosing regimens during online haemodiafiltration

Online haemodiafiltration (HDF) is increasingly used in clinical practice as a routine intermittent dialysis modality. It is well known that renal impairment and renal replacement therapy can substantially affect the pharmacokinetic behaviour of several drugs. However, surprisingly few data are available on the need for specific dose adjustments during HDF. Due to convection, drug clearance may be increased during HDF as compared with standard haemodialysis. This may be of particular interest in patients undergoing anti-infective therapy, since under-dosing may compromise patient outcomes and promote the emergence of bacterial resistance. Drug clearance during HDF is determined by (i) dialysis characteristics, (ii) drug characteristics and (iii) patient characteristics. In this review, we will discuss these different determinants of drug clearance during HDF and advise on how to adjust the dose of antibacterial, antimycotic and antiviral agents in patients undergoing HDF. In addition, the possible added value of therapeutic drug monitoring is discussed. The review provides guidance for optimization of anti-infective dosing regimens in HDF patients.

Predicting Maintenance Doses of Vancomycin for Hospitalized Patients Undergoing Hemodialysis

BACKGROUND

Methicillin-resistant Staphylococcus aureus is a leading cause of death in patients undergoing hemodialysis. However, controversy exists about the optimal dose of vancomycin that will yield the recommended pre-hemodialysis serum concentration of 15-20 mg/L.

OBJECTIVE

To develop a data-driven model to optimize the accuracy of maintenance dosing of vancomycin for patients undergoing hemodialysis.

METHODS

A prospective observational cohort study was performed with 164 observations obtained from a convenience sample of 63 patients undergoing hemodialysis. All vancomycin doses were given on the floor after completion of a hemodialysis session. Multivariate linear generalized estimating equation analysis was used to examine independent predictors of pre-hemodialysis serum vancomycin concentration.

RESULTS

Pre-hemodialysis serum vancomycin concentration was independently associated with maintenance dose (B = 0.658, p < 0.001), baseline pre-hemodialysis serum concentration of the drug (B = 0.492, p < 0.001), and interdialytic interval (B = -2.133, p < 0.001). According to the best of 4 models that were developed, the maintenance dose of vancomycin required to achieve a pre-hemodialysis serum concentration of 15-20 mg/L, if the baseline serum concentration of the drug was also 15-20 mg/L, was 5.9 mg/kg with interdialytic interval of 48 h and 7.1 mg/kg with interdialytic interval of 72 h. However, if the baseline pre-hemodialysis serum concentration was 10-14.99 mg/L, the required dose increased to 9.2 mg/kg with an interdialytic interval of 48 h and 10.0 mg/kg with an interdialytic interval of 72 h.

CONCLUSIONS

The maintenance dose of vancomycin varied according to baseline pre-hemodialysis serum concentration of the drug and interdialytic interval. The current practice of targeting a pre-hemodialysis concentration of 15-20 mg/L may be difficult to achieve for the majority of patients undergoing hemodialysis.

Vancomycin dosing and monitoring for patients with end-stage renal disease receiving intermittent hemodialysis

PURPOSE

Vancomycin dosing and monitoring algorithms for patients with end-stage renal disease (ESRD) receiving intermittent hemodialysis are reviewed.

SUMMARY

Vancomycin is one of the most commonly administered antimicrobial agents in adult patients with ESRD receiving intermittent hemodialysis. However, despite the availability of many published studies, the single best method of vancomycin administration in this population remains unclear. Many studies evaluating vancomycin dosing in adult patients with ESRD receiving intermittent hemodialysis were limited by a small sample size, inappropriate therapeutic targets, older hemodialysis modalities (e.g., low-flux intermittent hemodialysis), and inconsistencies in the timing of dosing or therapeutic drug monitoring. Pharmacokinetic variables that must be accounted for include a prolonged distribution phase, a redistribution phase and rebound effect after completion of hemodialysis, patient weight, residual renal function, and nonrenal clearance. Optimal vancomycin dosing recommendations are needed, but clinicians should always consider patient-specific variables, the timing of vancomycin administration, the timing of serum vancomycin concentrations, and technical aspects of the dialysis procedure when creating a dosing regimen.

CONCLUSION

Individualized vancomycin dosing regimens and therapeutic drug monitoring are necessary for patients with ESRD receiving intermittent hemodialysis to ensure that goal serum vancomycin levels are reached to adequately treat an infection.

Vancomycin: the tale of the vanquisher and the pyrrhic victory

Vancomycin has been the antibiotic of choice in the treatment of methicillin-resistant Staphylococcus aureus infections for decades. But relatively recently, vancomycin-intermediate-susceptible S. aureus (VISA) have been reported. Phenotypically, VISA are characterized by thicker cell walls, requiring higher concentrations of vancomycin for inhibition of bacterial cell growth. Vancomycin-intermediate-susceptible S. aureus represent just the tip of the iceberg of an insidious loss of vancomycin susceptibility in staphylococci. Increasing proportions of S. aureus isolates have higher minimum inhibitory concentrations that are still within the officially susceptible range, a characteristic that is associated with treatment failure. The most important risk factor for decreased vancomycin susceptibility is in vivo selection pressure. To prevent the development of VISA, prolonged or inappropriate use of vancomycin and suboptimal vancomycin levels should be avoided. Trough serum vancomycin concentrations of 15 - 20 mg/L for intermittent dosing and plateau serum vancomycin concentrations of 20 - 25 mg/L for continuous infusions are therefore currently recommended. The widespread clinical application of these intensive dosing regimens has resulted in an increasing awareness of vancomycin-induced nephrotoxicity, which is especially relevant in patients whose renal function is already compromised. This narrow therapeutic-toxic window reinforces the use of rigorous dosing protocols. In hemodialysis, the use of a vancomycin dose calculator permits achievement of target concentrations in most patients. In peritoneal dialysis (PD), intermittent vancomycin dosing regimens often lead to low end-of-dwell concentrations. On the other hand, a continuous vancomycin dosing regimen after a loading dose offers the desired combination of high local levels without toxic systemic levels.

Dosing of Gentamicin in Patients With End-Stage Renal Disease Receiving Hemodialysis

The aim of this study was to evaluate dosing schedules of gentamicin in patients with end-stage renal disease and receiving hemodialysis. Forty-six patients were recruited who received gentamicin while on hemodialysis. Each patient provided approximately 4 blood samples at various times before and after dialysis for analysis of plasma gentamicin concentrations. A population pharmacokinetic model was constructed using NONMEM (version 5). The clearance of gentamicin during dialysis was 4.69 L/h and between dialysis was 0.453 L/h. The clearance between dialysis was best described by residual creatinine clearance (as calculated using the Cockcroft and Gault equation), which probably reflects both lean mass and residual clearance mechanisms. Simulation from the final population model showed that predialysis dosing has a higher probability of achieving target maximum concentration (Cmax) concentrations (> 8 mg/L) within acceptable exposure limits (area under the concentration-time curve [AUC] values > 70 and < 120 mg x h/L per 24 hours) than postdialysis dosing.

In vitro Characterization of Oritavancin Clearance from Human Blood by Low-Flux, High-Flux, and Continuous Renal Replacement Therapy Dialyzers

Background

Oritavancin is an investigational lipoglycopeptide antibiotic under clinical development for the treatment of gram-positive bacterial infections. The impact of hemodialysis on plasma concentrations of oritavancin is unknown and may be important in making dosage adjustments in such patients. The present study sought to determine the clearance of oritavancin from human blood by various commercially available dialyzers in an in vitro hemodialysis model.

Methods

Three types each of low-flux (Dicea 130, F6, and Polyflux 14L) and high-flux (Revaclear, Exeltra 150, and Optiflux F160NR) dialyzers and one type of continuous renal replacement therapy (CRRT) dialyzer (Prismaflex M100) were studied. Heparinized human blood containing oritavancin (200 mg/L) was circulated from a reservoir to the dialyzers and back to the reservoir. Fresh dialysate was pumped through the dialyzers in a countercurrent manner. Blood samples from each side of the dialyzers and contaminated dialysate samples were collected at periodic intervals. Oritavancin levels were analyzed by a liquid chromatography/mass spectrometry method with a limit of quantification of 12.5 ng/mL and plasma clearances of oritavancin were calculated.

Results

The mean dialytic clearance of oritavancin was insignificant for each of the low-flux, high-flux and CRRT dialyzers. Clinically significant amounts of oritavancin were not detected in dialysate during any of the experimental dialysis sessions.

Conclusions

The clearance of oritavancin from human blood by the dialyzers used in this study is insignificant. Further clinical studies would be required before making changes in dosage of oritavancin in hemodialysis patients.

Prediction of failure in vancomycin-treated methicillin-resistant Staphylococcus aureus bloodstream infection: a clinically useful risk stratification tool

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of bloodstream infection (BSI) and is often associated with invasive infections and high rates of mortality. Vancomycin has remained the mainstay of therapy for serious Gram-positive infections, particularly MRSA BSI; however, therapeutic failures with vancomycin have been increasingly reported. We conducted a comprehensive evaluation of the factors (patient, strain, infection, and treatment) involved in the etiology and management of MRSA BSI to create a risk stratification tool for clinicians. This study included consecutive patients with MRSA BSI treated with vancomycin over 2 years in an inner-city hospital in Detroit, MI. Classification and regression tree analysis (CART) was used to develop a risk prediction model that characterized vancomycin-treated patients at high risk of clinical failure. Of all factors, the Acute Physiology and Chronic Health Evaluation II (APACHE-II) score, with a cutoff point of 14, was found to be the strongest predictor of failure and was used to split the population into two groups. Forty-seven percent of the population had an APACHE-II score < 14, a value that was associated with low rates of clinical failure (11%) and mortality (4%). Fifty-four percent of the population had an APACHE-II score ≥ 14, which was associated with high rates of clinical failure (35%) and mortality (23%). The risk stratification model identified the interplay of three other predictors of failure, including the vancomycin MIC as determined by Vitek 2 analysis, the risk level of the source of BSI, and the USA300 strain type. This model can be a useful tool for clinicians to predict the likelihood of success or failure in vancomycin-treated patients with MRSA bloodstream infection.

Vancomycin pharmacokinetics and pharmacodynamics during short daily hemodialysis

BACKGROUND AND OBJECTIVES

Short daily hemodialysis (SDHD) is an alternative to thrice-weekly HD because of its putative physiologic benefits. The purpose of this study was to investigate the effect of SDHD on the pharmacokinetics and pharmacodynamics of vancomycin.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Six noninfected adults who had anuria and were treated with SDHD were studied and received four dialysis sessions over 4 days. After completion of the first SDHD, each patient received vancomycin 15 mg/kg by intravenous infusion. Blood samples were collected over the ensuing 3 days during each subsequent inter- and intradialytic period. Pharmacokinetic parameters were determined. Serum concentration-time profiles were simulated for four vancomycin regimens with maintenance doses administered after every other SDHD. Area under the serum-concentration time curve (AUC) from 0 to 48 hours, 48 to 96 hours, and 96 to 144 hours were calculated, and Monte Carlo simulations were performed to determine the probability of target attainment at an AUC/minimum inhibitory concentration (MIC) ratio ≥800 for each 48-hour AUC at MICs ranging from 0.5 to 2.0 μg/ml.

RESULTS

Median (range) systemic clearance was 7.2 ml/min (5.3 to 10.0 ml/min), and dialytic clearance was 104 ml/min (94 to 106 ml/min). The steady-state volume of distribution was 55.4 L (34.8 to 77.2 L). At MICs ≤1 μg/ml, probability of target attainment was >90% for each 48-hour AUC when vancomycin was administered as a 20-mg/kg loading dose followed by 10 mg/kg after every other SDHD.

CONCLUSIONS

Vancomycin pharmacokinetic parameters in SDHD are consistent with data from thrice-weekly HD. A loading dose of 20 mg/kg followed by 10 mg/kg after every other SDHD provides adequate exposure for pathogens with MICs ≤1 μg/ml.

Intradialytic administration of daptomycin in end stage renal disease patients on hemodialysis

BACKGROUND AND OBJECTIVES

Infusion of intravenous antibiotics after hemodialysis (HD) may delay initiation of treatment for the next HD shift. Intradialytic administration of drugs such as vancomycin during the final hour of HD obviates these delays. Daptomycin has potent activity against Gram-positive bacteria, but the manufacturer recommends that the dose be infused after HD ends. This study determined the pharmacokinetics of intradialytically dosed daptomycin in patients with ESRD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This prospective crossover study compared single-dose daptomycin (6 mg/kg, 30-min intravenous infusion) pharmacokinetics administered after HD versus during the last part of HD with high-permeability (HP) and low-permeability (LP) dialyzers to seven patients who had ESRD and were on thrice-weekly HD. Serial blood samples were collected to determine daptomycin serum concentrations and protein binding. Statistical analysis was done using linear mixed model analysis.

RESULTS

The maximum serum concentration observed with a 6 mg/kg post-HD dose was 61.1 +/- 7.6 microg/ml with a mean protein binding of 89.2%. Intradialytic daptomycin administration resulted in reduced maximum serum concentration and area under the curve values that were approximately 12 to 20% lower when administered during HD with LP dialyzers and approximately 35% lower with HP dialyzers.

CONCLUSIONS

Intradialytic daptomycin administration during the last 30 min of HD is feasible, provided that larger dosages are used to compensate for intradialytic drug loss. On the basis of our findings, intradialytic doses of approximately 7 mg/kg (LP) or approximately 9 mg/kg (HP) theoretically should be bioequivalent to 6 mg/kg infused after HD. The calculated dosages are mathematically driven and must be validated in prospective clinical trials.

Assessment of vancomycin use in chronic haemodialysis patients: room for improvement

BACKGROUND

Vancomycin is frequently prescribed for the management of infections in haemodialysis patients. We evaluated the appropriateness of vancomycin use in our chronic haemodialysis population.

METHODS

Charts of all chronic haemodialysis patients who received vancomycin between 1 March 2003 and 1 March 2004 were retrospectively reviewed. Indication was assessed according to the modified Hospital Infection Control Practices Advisory Committee guidelines for vancomycin prescription. The prescribed dosing regimens were evaluated.

RESULTS

A total of 163 courses of vancomycin in 105 patients were assessed. Of all courses, 88% were considered to be initially appropriate, but this decreased to 63% once culture and sensitivity results were available. Use of vancomycin for the management of beta-lactam-sensitive organisms accounted for the majority of inappropriate use. The most common vancomycin-dosing regimen prescribed was 500 mg intravenously at each haemodialysis session (51%); however, considerable variability was observed.

CONCLUSIONS

Although the initial indication for vancomycin use was generally appropriate, inappropriate continuation of this antibiotic, failure to obtain proper cultures to guide therapy and potentially subtherapeutic dosing regimens were some of the challenges identified. Centres providing chronic haemodialysis should take steps to optimize vancomycin prescription to improve clinical outcomes and reduce the risk of antimicrobial resistance.

Pharmacokinetic and Pharmacodynamic Aspects of Antibiotic Use in High-Risk Populations

The study of pharmacokinetics includes the absorption, distribution, metabolism, and elimination of drugs. The pharmacologic effect that a medication has on the body is known as pharmacodynamics. With antimicrobials, pharmacokinetic and pharmacodynamic parameters become especially important because of the association between host drug concentrations, microorganism eradication, and resistance. This article focuses on the pharmacokinetic changes that can occur with antimicrobials when they are used in patients at high risk of infections and how they influence pharmacodynamic effects. The populations described here include patients with obesity and diabetes mellitus, renal or hepatic failure, chronic lung disease, severe burns, and long-term prosthetic devices and the elderly.

Optimizing antimicrobial therapy for gram-positive bloodstream infections in patients on hemodialysis

Infections with gram-positive organisms are highly prevalent in hemodialysis patients and are a major cause of morbidity and mortality in this population. Antimicrobial therapy is widely used to treat these infections, and prolonged therapy with these agents is often necessary. Extensive use of antimicrobials in hemodialysis patients has resulted in a growing threat of resistance, especially among gram-positive bacteria such as Enterococcus spp and Staphylococcus aureus. Vancomycin-resistant enterococci and S. aureus isolates with reduced susceptibility to vancomycin are increasingly being reported in hemodialysis patients. Additionally, resistance of these organisms to newer agents, such as linezolid and daptomycin, has been documented. Appropriate utilization of antimicrobial therapy to treat these organisms requires an understanding of the pharmacokinetic and pharmacodynamic principles to optimize therapy and avoid adverse drug events. The pharmacokinetic and pharmacodynamic profile of antimicrobial agents can be significantly altered in patients with chronic kidney disease. This review will describe mechanisms of antimicrobial resistance among common gram-positive organisms. The pharmacokinetic and pharmacodynamic principles of cephalosporins, vancomycin, aminoglycosides, linezolid, and daptomycin and applications for use of these agents in the treatment of patients with bloodstream infections on hemodialysis are discussed.