Augmented Renal Clearance and How to Augment Antibiotic Dosing

Optimize Vancomycin Dose in Surgical Ward Patients with Augmented Renal Clearance Determined by Chronic Kidney Disease Epidemiology Collaboration Equation

Background

In the field of postoperative care, infections caused by Gram-positive bacteria pose a major clinical challenge. Vancomycin is a key therapeutic agent whose efficacy is greatly influenced by renal function, particularly by augmented renal clearance (ARC). The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) estimated glomerular filtration rate (eGFR) is an easy and commonly used method to predict ARC; however, it is not well studied to determine vancomycin dose. In this study, we examined the effectiveness of the CKD-EPI equation in determining ARC and optimizing the dose of vancomycin for surgical ward patients.

Methodology

A retrospective observational study was conducted to examine 158 surgical ward patients receiving vancomycin. Data on demographics, medical history, and vancomycin dosing were collected. Renal function was evaluated using the CKD-EPI equation, with ARC defined as eGFR ≥ 96.5 mL/min/1.73 m2. Vancomycin pharmacokinetics were calculated using the ClinCalc tool.

Results

ARC was in 54% of the patients. Compared with patients without ARC, those with ARC were younger and had lower serum creatinine levels. They also required higher vancomycin doses but had lower trough concentrations and 24-hour area-under-the-curve values. A significant correlation was observed between eGFR and vancomycin clearance, with eGFR > 96.5 mL/min/1.73 m2 necessitating higher vancomycin doses (>45 mg/kg/day) to achieve the desired area under the curve to minimum inhibitory concentration ratio.

Conclusion

For surgical ward patients with CKD-EPI eGFR ≥ 96.5 mL/min/1.73 m2, a vancomycin dosage of >45 mg/kg/day may be recommended to reach effective therapeutic levels. Overall, this study emphasizes the importance of tailoring vancomycin therapy depending on renal function to ensure efficacy and mitigate the risk of antimicrobial resistance in surgical ward patients.

Daptomycin Exposure Prediction With a Limited Sampling Strategy

BACKGROUND

Daptomycin is a cyclic lipopeptide antibiotic used to treat serious infectious endocarditis caused by Staphylococcus aureus . The pharmacodynamic parameter correlating best with efficacy is the ratio of the estimated area under the concentration (AUC 0-24 )-time curve to the minimum inhibitory concentration. The aim of the study is to develop a limited sampling strategy to estimate AUC 0-24 using a reduced number of samples.

METHODS

Sixty-eight daptomycin AUC 0-24 values were calculated for 50 White patients who underwent treatment for at least 5 consecutive days. Plasma concentrations were detected using a validated high-performance liquid chromatography-tandem mass spectrometry analytical method, with daptomycin-d5 as an internal standard. Multiple regression was used to evaluate the ability of 2 concentration-time points to predict the AUC 0-24 calculated from the entire pharmacokinetic profile. Prediction bias was calculated as the mean prediction error, whereas prediction precision was estimated as the mean absolute prediction error. The development and validation datasets comprised 40 and 10 randomly selected patients, respectively.

RESULTS

The AUC 0-24 (mg*h/L) was best estimated using the daptomycin trough concentration and plasma concentrations detected 2 hours after dosing. We calculated a mean prediction error of 1.6 (95% confidence interval, -10.7 to 10.9) and a mean absolute prediction error of 11.8 (95% confidence interval, 5.3-18.3), with 73% of prediction errors within ±15%.

CONCLUSIONS

An equation was developed to estimate daptomycin exposure (AUC 0-24 ), offering clinical applicability and utility in generating personalized dosing regimens, especially for individuals at high risk of treatment failure or delayed response.

Relationship of imipenem therapeutic drug monitoring to clinical outcomes in critically ill patients: a retrospective cohort study

The primary objective of this study was to evaluate the predictors associated with target concentration (non-)attainment of imipenem in critically ill patients. The secondary objective was to explore the correlation between achieving imipenem target concentrations and clinical outcomes of therapy. A retrospective cohort study was conducted in critically ill patients treated with imipenem. Clinical data were extracted from the patients' electronic medical records. The pharmacokinetic/pharmacodynamic target was defined as free imipenem concentrations above the minimum inhibitory concentration (MIC) of the pathogen at 100% (100%fT>MIC) of the dosing interval. Factors associated with the non-attainment of target concentrations were evaluated using binomial logistic regression. Kaplan-Meier analysis was used to investigate the correlation between (non-)attainment targets and 30-day mortality. A total of 406 patients were included, and 55.4% achieved the target of 100%fT>MIC. Regression analysis identified an initial daily dose of imipenem ≤ 2 g/day, augmented renal clearance, age ≤ 60 years, recent surgery, and absence of positive microbiology culture as risk factors for target non-attainment. Achieving the 100%fT>MIC target was significantly associated with clinical efficacy but not with 30-day mortality. Selective application of therapeutic drug monitoring in the early stages of imipenem treatment for critically ill patients can improve clinical outcomes. Further research should explore the potential benefits of TDM-guided dosing strategies for imipenem in critical care settings.

Application of Monte Carlo simulation to optimise the dosage regimen of meropenem in patients with augmented renal clearance for Pseudomonas aeruginosa infection

Objective

To optimise the dosing regimen of meropenem for treating Pseudomonas aeruginosa (PA) infections in critically ill patients with augmented renal clearance (ARC) using pharmacokinetic/pharmacodynamic (PK/PD) principles and Monte Carlo simulation (MCS).

Methods

This research involves an MCS based on PK data from patients with ARC and a minimum inhibitory concentration (MIC) distribution of PA. This study simplifies the methods section, focusing on the critical aspects of simulation and target values for effective treatment.

Results

The study highlights key findings and emphasises that tailored dosing based on bacterial MIC values is essential for patients with ARC. It also notes that empirical treatment in patients with ARC should consider the MIC distribution, with 2 g every (q) 6 h administered to achieve the PK/PD target, while 3 g q 6 h is effective in inhibiting resistance.

Conclusion

Tailored dosing based on bacterial MIC values is crucial for patients with ARC. Prolonged infusion time alone does not enhance efficacy. Empirical treatment in patients with ARC should consider MIC distribution; a dosage of 2 g q 6 h achieves the PK/PD target, while 3 g q 6 h (≥12 g daily) inhibits resistance.

Exposure levels and target attainment of piperacillin/tazobactam in adult patients admitted to the intensive care unit: a prospective observational study

PURPOSE

The objective of this study was to evaluate the exposure and the pharmacodynamic target attainment of piperacillin/tazobactam (PTZ) in adult critically ill patients.

METHODS

We conducted a prospective observational study in the intensive care unit (ICU) of the Hôpital du Sacré-Cœur de Montréal (a Level I trauma centre in Montreal, QC, Canada) between January 2021 and June 2022. We included patients aged 18 yr or older admitted to the ICU who received PTZ by intravenous administration. Demographic and clinical characteristics were collected, and clinical scores were calculated. On study day 1 of antimicrobial therapy, three blood samples were collected at the following timepoints: one hour after PTZ dose administration and at the middle and at the end of the dosing interval. The sampling schedule was repeated on days 4 and 7 of therapy if possible. Samples were analyzed by ultra-high performance liquid chromatography with diode array detector to determine the total piperacillin concentration. Middle- and end-of-interval concentrations were used for target attainment analyses, and were defined as a concentration above the minimal inhibitory concentration of 16 mg·L-1, corresponding to the breakpoint of Enterobacteriaceae and Pseudomonas aeruginosa.

RESULTS

Forty-three patients were recruited and 202 blood samples were analyzed. The most prevalent dose was 3/0.375 g every six hours (n = 50/73 doses administered, 68%) with a 30-min infusion. We observed marked variability over the three sampling timepoints, and the median [interquartile range] piperacillin concentrations at peak, middle of interval, and end of interval were 109.4 [74.0-152.3], 59.3 [21.1-74.4], and 25.3 [6.8-44.6] mg·L-1, respectively. When assessing target attainment, 37% of patients did not reach the efficacy target of a trough concentration of 16 mg·L-1. The majority of patients who were underexposed were patients with normal to augmented renal clearance.

CONCLUSION

In this prospective observational study of adult ICU patients receiving intravenous PTZ, a large proportion had subtherapeutic concentrations of piperacillin. This was most notable in patients with normal to augmented renal clearance. More aggressive dosage regimens may be required for this subpopulation to ensure attainment of efficacy targets.

Therapeutic drug monitoring of vancomycin in the case of augmented renal clearance: a case report of a paediatric patient

Augmented renal clearance (ARC) is a condition in which renal circulation increases, causing drug levels in the blood to remain at subtherapeutic levels in severe trauma patients. Vancomycin, a hydrophilic anti-Gram-positive drug, has been shown in the literature to have its levels fall below the therapeutic range in the case of ARC. However, vancomycin dosing recommendations in the case of ARC are still lacking. Here, we identify an ARC case measured with urinary creatinine clearance in a severe trauma paediatric patient, causing vancomycin blood trough levels to drop. We could not be able to increase the vancomycin trough levels with intermittent dosing; hence, we administered vancomycin with continuous infusion, and this resulted in vancomycin blood trough levels remaining in the therapeutic range. No adverse effect was seen. Continuous infusion of vancomycin can be safely administered to paediatric patients in these cases.

How to Dose Vancomycin in Overweight and Obese Patients with Varying Renal (Dys)function in the Novel Era of AUC 400-600 mg·h/L-Targeted Dosing

BACKGROUND AND OBJECTIVE

The latest vancomycin guideline recommends area under the curve (AUC)-targeted dosing and monitoring for efficacy and safety. However, guidelines for AUC-targeted starting dosing in patients with obesity and/or renal insufficiency are currently lacking. This study quantifies the pharmacokinetics (PK) of vancomycin in this population and provides AUC-targeted dosing recommendations.

METHODS

Vancomycin concentrations (n = 1188) from therapeutic drug monitoring of 210 overweight and obese patients with varying degrees of renal (dys)function from the ward (74.8%) and intensive care unit (ICU, 25.2%) were pooled with published rich concentration-time data (n = 207) from 20 (morbidly) obese subjects undergoing bariatric surgery. A population model was developed using NONMEM 7.4. Stochastic simulations were performed to design dosing guidelines targeting an AUC24 between 400-600 mg·h/L.

RESULTS

Vancomycin clearance (CL) was found to increase linearly with total bodyweight and with renal function (CKD-EPI) in a power relation. Additionally, CL proved 15.5% lower in ICU patients. Our model shows that, to reach the target AUC between 400 and 600 mg·h/L in the first 48 h, two loading doses are required for both continuous infusion and intermittent dosing regimens. Maintenance doses were found to require adjustment for total bodyweight, renal function, and ICU admission status. With this guideline, the median AUC24 is well within the target from the start of the treatment onwards.

CONCLUSIONS

To achieve safe and effective vancomycin exposure for maintenance doses in overweight and obese patients, renal function, total bodyweight, and ICU admission status should be taken into account.

TRIAL REGISTRATION

The AMIGO trial was registered in the Dutch Trial Registry [NTR6058].

Antimicrobial treatment imprecision: an outcome-based model to close the data-to-action loop

Health-care systems, food supply chains, and society in general are threatened by the inexorable rise of antimicrobial resistance. This threat is driven by many factors, one of which is inappropriate antimicrobial treatment. The ability of policy makers and leaders in health care, public health, regulatory agencies, and research and development to deliver frameworks for appropriate, sustainable antimicrobial treatment is hampered by a scarcity of tangible outcome-based measures of the damage it causes. In this Personal View, a mathematically grounded, outcome-based measure of antimicrobial treatment appropriateness, called imprecision, is proposed. We outline a framework for policy makers and health-care leaders to use this metric to deliver more effective antimicrobial stewardship interventions to future patient pathways. This will be achieved using learning antimicrobial systems built on public and practitioner engagement; solid implementation science; advances in artificial intelligence; and changes to regulation, research, and development. The outcomes of this framework would be more ecologically and organisationally sustainable patterns of antimicrobial development, regulation, and prescribing. We discuss practical, ethical, and regulatory considerations involved in the delivery of novel antimicrobial drug development, and policy and patient pathways built on artificial intelligence-augmented measures of antimicrobial treatment imprecision.

State of the Management of Infections Caused by Multidrug-Resistant Gram-Negative Organisms

In the past decade, the prevalence of multidrug-resistant gram-negative (MDR-GN) bacterial infections has increased significantly, leading to higher rates of morbidity and mortality. Treating these infections poses numerous challenges, particularly when selecting appropriate empiric therapy for critically ill patients for whom the margin for error is low. Fortunately, the availability of new therapies has improved the treatment landscape, offering safer and more effective options. However, there remains a need to establish and implement optimal clinical and therapeutic approaches for managing these infections. Here, we review strategies for identifying patients at risk for MDR-GN infections, propose a framework for the choice of empiric and definitive treatment, and explore effective multidisciplinary approaches to managing patients in the hospital while ensuring a safe transition to outpatient settings.

Real-Life Vancomycin Therapeutic Drug Monitoring in Coagulase-Negative Staphylococcal Bacteremia in Neonatal and Pediatric Intensive Care Unit: Are We Underestimating Augmented Renal Clearance?

Bloodstream infections (BSI) from coagulase-negative-staphylococci (CoNS) are among the most frequent healthcare-related infections. Their treatment involves the use of vancomycin, a molecule whose optimal pharmacokinetic/pharmacodynamic (PK/PD) target for efficacy and safety is an area-under-curve/minimum inhibitory concentration (AUC/MIC) ratio ≥ 400 with AUC < 600. BSIs from CoNS in pediatric and neonatal intensive care unit that occurred at the Gaslini Institute over five years were evaluated to investigate the efficacy of vancomycin therapy in terms of achieving the desired PK/PD target and determining whether any variables interfere with the achievement of this target. AUC/MIC ≥ 400 with AUC < 600 at 48 and 72 h after therapy initiation was achieved in only 21% of the neonatal population and 25% of the pediatric population. In the pediatric population, an inverse correlation emerged between estimated glomerular filtration rate (eGFR) and achieved AUC levels. Median eGFR at 72 h was significantly higher (expression of hyperfiltration) in events with AUC < 400, compared with those with AUC ≥ 400 (p < 0.001). A cut-off value of eGFR in the first 72 h has been identified (145 mL/min/1.73 m2), beyond which it is extremely unlikely to achieve an AUC ≥ 400, and therefore a higher dose or a different antibiotic should be chosen.

Treatment implications of augmented renal clearance in a critically ill COVID-19 patient: A case report

Augmented renal clearance (ARC) is a pathophysiological phenomenon that can occur in critically ill patients, leading to enhanced renal function. It is defined as a creatinine clearance of >130 mL/min/1.73 m2 . ARC can lead to subtherapeutic levels of renally cleared drugs and subsequent treatment failure. In COVID-19, it has only been described in the literature in a few cases. We present the case of a 38-year-old critically ill patient with COVID-19 who developed ARC with an initial clearance of 226 mL/min/1.73 m2 , persisting for 30 days. He required high doses of sedatives and neuromuscular blocking agents, as well as increased doses of vancomycin and dalteparin, to reach adequate serum levels. This case emphasizes the importance for clinicians to consider ARC in the dosing of all renally cleared drugs, including antibiotics, low molecular weight heparins, and sedatives, to prevent subtherapeutic drug levels and treatment failure.

Creatinine Clearance in Acute Brain Injury: A Comparison of Methods

BACKGROUND

Currently, the measurement of glomerular filtration rate is very complex and costly, so its daily evaluation is performed using endogenous markers, of which creatinine is the most frequently used. It allows the estimation of glomerular filtration rate by means of its clearance or by formulas based on its serum and urine concentration. Augmented renal clearance (ARC) is frequent among critically ill patients and is defined as creatinine clearance (CrCl) > 130 ml/min/1.73 m2. The aim of this study was to compare measured CrCl (MCC) and estimated CrCl obtained with the Cockcroft-Gault formula (CG), the Modification of Diet in Renal Disease Study equation (MDRD), and the Chronic Kidney Disease Epidemiology Collaboration formula (CKD-EPI) in patients with severe traumatic brain injury and nontraumatic subarachnoid hemorrhage. The second aim was to assess the incidence of ARC in this population of neurocritical patients.

METHODS

This was a prospective, observational, single center study from a cohort of 74 patients admitted to the neurocritical intensive care unit due to traumatic brain injury or subarachnoid hemorrhage. Serum creatinine (at 7 a.m.) and a 6-h urine collection were analyzed, and CrCl was measured and estimated by using CG, MDRD, and CKD-EPI. The intraclass correlation coefficient (ICC) was evaluated for each pair, and Bland-Altman plots were used to assess clinical significance.

RESULTS

Among 74 patients, the median age was 53 (interquartile range [IQR] 36-65), and the median Glasgow Coma Scale score at admission was 6. The median MCC at admission was 176 (IQR 135-214). The medians of CG, MDRD and CKD-EPI were, respectively, 129 ml/min/1.73 m2 (IQR 95-176), 158 (IQR 115-202), and 116 (97-132). An ICC was applied to evaluate the correlation between MCC and estimated methods and showed a weak correlation between MCC and estimated CrCl obtained with the three different methods. The strongest ICC statistical correlation was found between MCC and MDRD, and the weakest correlation was found between MCC and CKD-EPI. Bland-Altman plots showed that differences between each pair were not clinically acceptable. ARC was present in 78% of measurements, using MCC. A weak correlation was observed between MCC and calculated CrCl. CG, MDRD, and CKD-EPI overestimated MCC when MCC ≤ 130 ml/min/1.73 m2 and underestimated it when MCC > 130 ml/min/1.73 m2.

CONCLUSIONS

In this population, there was a weak statistical correlation between measured and estimated methods. In patients with ARC, formulas underestimated MCC. MCC should probably be the preferred methodology for renal function assessment in the clinical setting to better adjust drug dosage and guarantee drug effectiveness.

Population Pharmacokinetic Modeling and Dose Optimization of Acetaminophen and its Metabolites Following Intravenous Infusion in Critically ill Adults

BACKGROUND AND OBJECTIVE

Acetaminophen (paracetamol) is a ubiquitously administered drug in critically ill patients. Considering the dearth of literature, we evaluated the population pharmacokinetics of intravenous acetaminophen and its principal metabolites (sulfate and glucuronide) in this population.

METHODS

Critically ill adults receiving intravenous acetaminophen were included in the study. One to three blood samples were withdrawn per patient for the estimation of acetaminophen, and its metabolites (acetaminophen glucuronide and acetaminophen sulfate). High-performance liquid chromatography was used for measuring serum concentrations. We used nonlinear mixed-effect modeling for estimating the primary pharmacokinetic parameters of acetaminophen and its metabolites. The effect of covariates was evaluated followed by dose optimization using Monte Carlo simulation. Patient factors such as demographic information, liver and renal function tests were used as covariates in population pharmacokinetic analysis. The therapeutic range for serum acetaminophen concentration was considered to be 66-132 μM, while 990 μM was considered as the threshold for toxic concentration.

RESULTS

Eighty-seven participants were recruited. A joint two-compartment acetaminophen pharmacokinetic model linked to glucuronide and sulfate metabolite compartments was used. The central and peripheral volume distributions were 7.87 and 8.87 L/70 kg, respectively. Estimated clearance (CL) was 0.58 L/h/70 kg, while intercompartmental clearance was 44.2 L/h/70 kg. The glucuronide and sulfate metabolite CL were 22 and 94.7 L/h/70 kg, respectively. Monte Carlo simulation showed that twice-daily administration of acetaminophen would result in a relatively higher proportion of patient population achieving and retaining serum concentrations in the therapeutic range, with reduced risk of concentrations remaining in the toxic range.

CONCLUSION

A joint pharmacokinetic model for intravenous acetaminophen and its principal metabolites in a critically ill patient population has been developed. Acetaminophen CL in this patient population is reduced. We propose a reduction in the frequency of administration to reduce the risk of supra-therapeutic concentrations in this population.

Pharmacokinetics of Antibacterial Agents in the Elderly: The Body of Evidence

Infections are important factors contributing to the morbidity and mortality among elderly patients. High rates of consumption of antimicrobial agents by the elderly may result in increased risk of toxic reactions, deteriorating functions of various organs and systems and leading to the prolongation of hospital stay, admission to the intensive care unit, disability, and lethal outcome. Both safety and efficacy of antibiotics are determined by the values of their plasma concentrations, widely affected by physiologic and pathologic age-related changes specific for the elderly population. Drug absorption, distribution, metabolism, and excretion are altered in different extents depending on functional and morphological changes in the cardiovascular system, gastrointestinal tract, liver, and kidneys. Water and fat content, skeletal muscle mass, nutritional status, use of concomitant drugs are other determinants of pharmacokinetics changes observed in the elderly. The choice of a proper dosing regimen is essential to provide effective and safe antibiotic therapy in terms of attainment of certain pharmacodynamic targets. The objective of this review is to perform a structure of evidence on the age-related changes contributing to the alteration of pharmacokinetic parameters in the elderly.

Altered Pharmacokinetics Parameters of Vancomycin in Patients with Hematological Malignancy with Febrile Neutropenia, a Bayesian Software Estimation

The pharmacokinetics of vancomycin vary significantly between specific groups of patients, such as critically ill patients and patients with hematological malignancy (HM) with febrile neutropenia (FN). Recent evidence suggests that the use of the usual standard dose of antibiotics in patients with FN may not offer adequate exposure due to pharmacokinetic variability (PK). Therefore, the purpose of this study is to assess the effect of FN on AUC_0-24 as a key parameter for vancomycin monitoring, as well as to determine which vancomycin PK parameters are affected by the presence of FN using Bayesian software PrecisePK in HM with FN. This study was carried out in King Abdulaziz Medical City. All adult patients who were admitted to the Princess Norah Oncology Center PNOC between 1 January and 2017 and 31 December 2020, hospitalized and received vancomycin with a steady-state trough concentration measured before the fourth dose, were included. During the trial period, 297 patients received vancomycin during their stay at the oncology center, 217 of them meeting the inclusion criteria. Pharmacokinetic parameters were estimated for the neutropenic and non-FN patients using the precise PK Bayesian platform. The result showed that there was a significant difference (p < 0.05) in vancomycin clearance Cl_van, the volume of distribution at a steady-state V_dss, the volume of distribution for peripheral compartment V_dp, half-life for the elimination phase t½_β, and the first-order rate constant for the elimination process β in FN compared to non-FN patients. Furthermore, AUC_0-24 was lower for FN patients compared to non-FN patients, p < 0.05. FN has a significant effect on the PK parameters of vancomycin and AUC_0-24, which may require specific consideration during the treatment initiation.

Optimizing Vancomycin Therapy in Critically Ill Children: A Population Pharmacokinetics Study to Inform Vancomycin Area under the Curve Estimation Using Novel Biomarkers

Area under the curve (AUC)-directed vancomycin therapy is recommended, but Bayesian AUC estimation in critically ill children is difficult due to inadequate methods for estimating kidney function. We prospectively enrolled 50 critically ill children receiving IV vancomycin for suspected infection and divided them into model training (n = 30) and testing (n = 20) groups. We performed nonparametric population PK modeling in the training group using Pmetrics, evaluating novel urinary and plasma kidney biomarkers as covariates on vancomycin clearance. In this group, a two-compartment model best described the data. During covariate testing, cystatin C-based estimated glomerular filtration rate (eGFR) and urinary neutrophil gelatinase-associated lipocalin (NGAL; full model) improved model likelihood when included as covariates on clearance. We then used multiple-model optimization to define the optimal sampling times to estimate AUC24 for each subject in the model testing group and compared the Bayesian posterior AUC24 to AUC24 calculated using noncompartmental analysis from all measured concentrations for each subject. Our full model provided accurate and precise estimates of vancomycin AUC (bias 2.3%, imprecision 6.2%). However, AUC prediction was similar when using reduced models with only cystatin C-based eGFR (bias 1.8%, imprecision 7.0%) or creatinine-based eGFR (bias -2.4%, imprecision 6.2%) as covariates on clearance. All three model(s) facilitated accurate and precise estimation of vancomycin AUC in critically ill children.

Imipenem/cilastatin/relebactam efficacy, safety and probability of target attainment in adults with hospital-acquired or ventilator-associated bacterial pneumonia among patients with baseline renal impairment, normal renal function, and augmented renal clearance

Objectives

To assess the relationship between renal function and efficacy/safety of imipenem/cilastatin/relebactam for the treatment of hospital-acquired/ventilator-associated pneumonia (HABP/VABP) from RESTORE-IMI 2 and determine the PTA.

Methods

Adults with HABP/VABP were randomized 1:1 to IV imipenem/cilastatin/relebactam 1.25 g or piperacillin/tazobactam 4.5 g every 6 h for 7-14 days. Initial doses were selected by CL_CR and adjusted thereafter, as appropriate. Outcomes included Day 28 all-cause mortality (ACM), clinical response, microbiological response and adverse events. Population pharmacokinetic modelling and Monte Carlo simulations assessed PTA.

Results

The modified ITT population comprised those with normal renal function (n = 188), augmented renal clearance (ARC; n = 88), mild renal impairment (RI; n = 124), moderate RI (n = 109) and severe RI (n = 22). ACM rates were comparable between treatment arms among all baseline renal function categories. Clinical response rates were comparable between treatment arms for participants with RI and normal renal function but were higher (91.7% versus 44.4%) for imipenem/cilastatin/relebactam-treated versus piperacillin/tazobactam-treated participants with CL_CR ≥250 mL/min (n = 21). Microbiologic response rates were comparable between treatment arms for participants with RI but higher among those treated with imipenem/cilastatin/relebactam in participants with CL_CR ≥90 mL/min (86.6% versus 67.2%). Adverse events were comparable between treatment arms across renal function categories. Joint PTA was >98% for key pathogen MICs for susceptible pathogens (MIC ≤2 mg/L).

Conclusions

Prescribing information-defined dose adjustments in participants with baseline RI and full dosing of imipenem/cilastatin/relebactam 1.25 g every 6 h for participants with normal renal function or augmented renal clearance achieved sufficiently high drug exposures and favourable safety and efficacy profiles.

An Unusual Case of Low Vancomycin Exposure Despite Extremely High Vancomycin Doses Accompanied by Renal Toxicity: A Grand Round

ABSTRACT

This grand round describes the case of a patient who received 10 grams (143.5 mg/kg) of vancomycin every 24 hours via continuous infusion, in whom the highest observed level was only 15.4 mg/L. Despite subtherapeutic levels, renal impairment was encountered, which resolved after the discontinuation of vancomycin. Glomerular hyperfiltration was found through nuclear glomerular filtration rate measurement, which likely explains the need for high doses (>6 grams per 24 hours continuous infusion) without reaching therapeutic serum levels.

Impact of piperacillin unbound fraction variability on dosing recommendations in critically ill patients

A common approach to assess the efficacy of piperacillin is to first measure the total concentration and afterwards apply a theoretical unbound fraction of 70% to obtain the unbound concentration. However, hypoalbuminemia is a common phenomenon in critically ill patients, resulting in variations in unbound fraction, therefore we aimed to simulate the impact of piperacillin unbound fraction fluctuations on the predictive performance of a population pharmacokinetic model and on the dosing recommendations of piperacillin. Unbound factors of 70%, 75%, 80% and 85% were applied to total concentrations of piperacillin administered by continuous infusion from an external dataset. A validated model was used for assessment of predictive performance and to estimate patient clearance. Dosing simulations were performed to evaluate target attainment. Variation in unbound fractions caused minimal impact on piperacillin clearance and target attainment but seemed to influence model validity.

Critically Ill Patients with Renal Hyperfiltration: Optimizing Antibiotic Dose

Renal hyperfiltration (RHF) is a prevalent phenomenon in critically ill patients characterized by augmented renal clearance (ARC) and increased of elimination of renally eliminated medications. Multiple risk factors had been described and potential mechanisms may contribute to the occurrence of this condition. RHF and ARC are associated with the risk of suboptimal exposure to antibiotics increasing the risk of treatment failure and unfavorable patient outcomes. The current review discusses the available evidence related to the RHF phenomenon, including definition, epidemiology, risk factors, pathophysiology, pharmacokinetic variability, and considerations for optimizing the dosage of antibiotics in critically ill patients.

Pharmacokinetics of Antimicrobials in Children with Emphasis on Challenges Faced by Low and Middle Income Countries, a Clinical Review

Effective antimicrobial exposure is essential to treat infections and prevent antimicrobial resistance, both being major public health problems in low and middle income countries (LMIC). Delivery of drug concentrations to the target site is governed by dose and pharmacokinetic processes (absorption, distribution, metabolism and excretion). However, specific data on the pharmacokinetics of antimicrobials in children living in LMIC settings are scarce. Additionally, there are significant logistical constraints to therapeutic drug monitoring that further emphasize the importance of understanding pharmacokinetics and dosing in LMIC. Both malnutrition and diarrheal disease reduce the extent of enteral absorption. Multiple antiretrovirals and antimycobacterial agents, commonly used by children in low resource settings, have potential interactions with other antimicrobials. Hypoalbuminemia, which may be the result of malnutrition, nephrotic syndrome or liver failure, increases the unbound concentrations of protein bound drugs that may therefore be eliminated faster. Kidney function develops rapidly during the first years of life and different inflammatory processes commonly augment renal clearance in febrile children, potentially resulting in subtherapeutic drug concentrations if doses are not adapted. Using a narrative review approach, we outline the effects of growth, maturation and comorbidities on maturational and disease specific effects on pharmacokinetics in children in LMIC.

Evaluation of vancomycin pharmacokinetics in patients with augmented renal clearances: A randomized clinical trial

Purpose: Vancomycin is a narrow therapeutic window glycopeptide antibiotic that acts against Gram-positive bacteria. As it is renally eliminated, therapeutic drug monitoring is recommended for vancomycin, especially in case of kidney function alteration. Augmented renal clearance (ARC), defined as a creatinine clearance of more than 130 ml/min, is a risk factor for sub-therapeutic concentrations of vancomycin. This study aimed to evaluate the vancomycin pharmacokinetics following the administration of two different regimens in ARC patients.

Methods: A randomized clinical trial (IRCT20180802040665N1) was conducted on patients in need of vancomycin therapy. Eight hours of urine was collected and 56 patients divided into two groups with creatinine clearance of more than 130 ml/min were included in the study. The first group received 15 mg/kg of vancomycin every 12 h and the second group 15 mg/kg every 8 h. After four doses, the peak and trough concentrations were measured from two blood samples. The primary outcome was the percentage of patients who attainted AUC more than 400. The occurrence of acute kidney injury also was evaluated after seven days.

Results: The mean age of patients in the every 12 h and every 8 h groups was 44.04 ± 16.55 and 42.86 ± 11.83 years, respectively. While neurosurgical issues were the most common causes of hospitalization, central nervous infections were the most common indications for vancomycin initiation. Urinary creatinine clearance was 166.94 ± 41.32 ml/min in the every 12 h group and 171.78 ± 48.56 ml/min in the every 8 h group. 46.42% of patients in the every 12 h group and 82.14% of patients in the every 8 h group attained AUC/MIC of more than 400 mg × hr/L. None of the patients in the every 12 h group reached more than 15 mcg/ml concentration. At the 7-day follow-up, 10.7% patients in the BD group and 28.6% patients in the TDS group developed acute kidney injury (p = 0.089).

Conclusion: Administration of vancomycin at a dose of 15 mg/kg every 8 h is associated with higher pharmacokinetic attainment in ARC patients. The occurrence of acute kidney injury also was not significantly higher in this therapeutic regimen. AUC/MIC monitoring is necessary in this population.

Tissue Penetration of Antimicrobials in Intensive Care Unit Patients: A Systematic Review-Part II

In patients that are admitted to intensive care units (ICUs), the clinical outcome of severe infections depends on several factors, as well as the early administration of chemotherapies and comorbidities. Antimicrobials may be used in off-label regimens to maximize the probability of therapeutic concentrations within infected tissues and to prevent the selection of resistant clones. Interestingly, the literature clearly shows that the rate of tissue penetration is variable among antibacterial drugs, and the correlation between plasma and tissue concentrations may be inconstant. The present review harvests data about tissue penetration of antibacterial drugs in ICU patients, limiting the search to those drugs that mainly act as protein synthesis inhibitors and disrupting DNA structure and function. As expected, fluoroquinolones, macrolides, linezolid, and tigecycline have an excellent diffusion into epithelial lining fluid. That high penetration is fundamental for the therapy of ventilator and healthcare-associated pneumonia. Some drugs also display a high penetration rate within cerebrospinal fluid, while other agents diffuse into the skin and soft tissues. Further studies are needed to improve our knowledge about drug tissue penetration, especially in the presence of factors that may affect drug pharmacokinetics.

Expert consensus statement on therapeutic drug monitoring and individualization of linezolid

Linezolid is an oxazolidinone antibacterial drug, and its therapeutic drug monitoring and individualized treatment have been challenged since its approval. With the in-depth clinical research of linezolid, we have changed our attitude toward its therapeutic drug monitoring and our view of individualized treatment. On the basis of summarizing the existing clinical studies, and based on the practical experience of each expert in their respective professional fields, we have formed this expert consensus. Our team of specialists is a multidisciplinary team that includes pharmacotherapists, clinical pharmacology specialists, critical care medicine specialists, respiratory specialists, infectious disease specialists, emergency medicine specialists and more. We are committed to the safe and effective use of linezolid in patients in need, and the promotion of its therapeutic drug monitoring.

Risk factors associated with augmented renal clearance in a mixed intensive care unit population: a retrospective study

BACKGROUND

Augmented renal clearance is increasingly recognized in critically ill patients. This condition may lead to suboptimal dosing of renally excreted medications.

AIM

Our primary objective was to identify demographic and clinical factors associated with augmented renal clearance in a mixed critically ill population.

METHOD

This retrospective single center observational cohort study evaluated patients admitted in a mixed adult intensive care unit for augmented renal clearance, defined as a creatinine clearance of ≥ 130 ml/min/1.73m²_, through weekly 24-h urine collection. Variables associated with augmented renal clearance were identified using univariate analysis, then served as covariates in a backward stepwise logistic regression. Goodness-of-fit of the model was assessed and receiver operating characteristic curve was generated.

RESULTS

Augmented renal clearance was observed in 25.3% of the study cohort (n = 324). Age below 50 years (adjusted odds ratio 7.32; 95% CI 4.03-13.29, p < 0.001), lower serum creatinine at intensive care admission (adjusted odds ratio 0.97; 95% CI 0.96-0.99, p < 0.001) and trauma admission (adjusted odds ratio 2.26; 95% CI 1.12-4.54, p = 0.022) were identified as independent risk factors. Our model showed acceptable discrimination in predicting augmented renal clearance (Area under receiver operating characteristic curve (0.810; 95% CI 0.756-0.864, p < 0.001)).

CONCLUSION

We identified age below 50 years, lower serum creatinine upon intensive care admission and trauma as independent risk factors for augmented renal clearance, consistent with the literature suggesting that patients with low serum creatinine upon admission could have a higher risk of developing augmented renal clearance.

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.

Pharmacokinetic variability of vancomycin in patients with nosocomial meningitis

WHAT IS KNOWN AND OBJECTIVE

High doses of vancomycin are required early in the treatment of nosocomial meningitis. However, the dosage is often reduced later during treatment, irrespective of renal function. This study was designed to investigate the pharmacokinetic variability of vancomycin and the associated factors throughout the treatment course for patients with nosocomial bacterial meningitis.

METHODS

This study included 17 patients who received vancomycin for nosocomial bacterial meningitis at the Tokyo Women's Medical University Yachiyo Medical Center from April 2013 to May 2020. All patients had their serum vancomycin concentrations and cerebrospinal fluid (CSF) parameters measured within 7 days of initiating treatment (early period) and after 8 days (later period) of treatment.

RESULTS AND DISCUSSION

The relative error between the predicted serum vancomycin concentration and the measured value was significantly higher in the later period than in the early period. In 13 patients who did not have their dosing interval shortened, the vancomycin dosage/serum vancomycin concentration/estimated glomerular filtration rate (D/C/eGFR) ratio significantly decreased in the later period. Moreover, the rate of change in the D/C/eGFR ratio significantly correlated with that in the CSF protein and C-reactive protein levels.

WHAT IS NEW AND CONCLUSION

This study suggests that the clinical condition and inflammatory response of a patient with meningitis influence the pharmacokinetics of vancomycin. Therefore, the vancomycin dosage for the treatment of nosocomial bacterial meningitis must be adjusted according to changes in the clinical condition and renal function of the patient, necessitating careful therapeutic drug monitoring.

Plasma trough concentration distribution and safety of high-dose teicoplanin for patients with augmented renal clearance

WHAT IS KNOWN AND OBJECTIVE

There are few reports on the distribution of the plasma trough concentration (C_min ) of teicoplanin in patients with augmented renal clearance (ARC) and on the safety of a high-dose regimen (HD; 800 mg loading dose for q12h three times followed by an 800 mg qd maintenance dose). The objective of this study was to determine the C_min values of teicoplanin in ARC patients using HD teicoplanin to provide a reference for individualized medication.

METHODS

Data on patients treated with teicoplanin from January 2019 to January 2021 were collected retrospectively and divided into ARC (creatinine clearance rate [CCr] >130 ml/min, n = 22) and non-ARC (60 ml/min ≤ CCr ≤130 ml/min, n = 24) groups. The C_min values in the two patient groups were analysed during the HD and the low-dose regimen (LD; all other regimens) on the third day of medication and during the dose maintenance period. Liver and kidney function indexes were also analysed before and after medication.

RESULTS AND DISCUSSIONS

On the third day of the HD, C_min did not differ significantly between the ARC and non-ARC groups (17.3 ± 9.2 mg/L [mean ± SD] vs. 15.5 ± 7.9 mg/L, p = 0.663), while C_min in the ARC group was significantly lower for the LD (6.8 ± 3.9 mg/L, p = 0.039). During the dose maintenance period, C_min in the ARC group when receiving the HD (18.3 ± 5.1 mg/L) was significantly lower than that in the non-ARC group (25.5 ± 11.9 mg/L, p = 0.016) and significantly higher than that for the LD (12.2 ± 6.3 mg/L, p = 0.022). Nephrotoxicity and hepatotoxicity incidence rates did not differ significantly between these groups.

WHAT IS NEW AND CONCLUSION

These results suggest that it is necessary to apply a loading dose of 800 mg (but not higher) q12h three times for patients with ARC, with 800 mg needed as a maintenance dose during severe infection, and 600 mg or 400 mg for mild infection.

Pharmacokinetics of piperacillin and tazobactam in critically Ill patients treated with continuous kidney replacement therapy: A mini-review and population pharmacokinetic analysis

WHAT IS KNOWN AND OBJECTIVE

Timely and appropriate dosing of antibiotics is essential for the treatment of bacterial sepsis. Critically ill patients treated with continuous kidney replacement therapy (CKRT) often have physiologic derangements that affect pharmacokinetics (PK) of antibiotics and dosing may be challenging. We sought to aggregate previously published piperacillin and tazobactam (pip-tazo) pharmacokinetic data in critically ill patients undergoing CKRT to better understand pharmacokinetics of pip-tazo in this population and better inform dosing.

METHODS

The National Library of Medicine Database was searched for original research containing piperacillin or tazobactam clearance (CL) or volume of distribution (V) estimates in patients treated with CKRT. The search yielded 77 articles, of which 26 reported suitable estimates of CL or V. Of the 26 articles, 10 for piperacillin and 8 for tazobactam had complete information suitable for population pharmacokinetic modelling. Also included in the analysis was piperacillin and tazobactam PK data from 4 critically ill patients treated with CKRT in the Military Health System, 2 with burn and 2 without burn.

RESULTS AND DISCUSSION

Median and range of literature reported PK parameters for piperacillin (CL 2.76 L/hr, 1.4-7.92 L/hr, V 31.2 L, 16.77-42.27 L) and tazobactam (CL 2.34 L/hr, 0.72-5.2 L/hr, V 36.6 L, 26.2-58.87 L) were highly consistent with population estimates (piperacillin CL 2.7 L/hr, 95%CI 1.99-3.41 L/hr, V 25.83 22.07-29.59 L, tazobactam CL 2.49 L/hr, 95%CI 1.55-3.44, V 30.62 95%CI 23.7-37.54). The proportion of patients meeting pre-defined pharmacodynamic (PD) targets (median 88.7, range 71%-100%) was high despite significant mortality (median 44%, range 35%-60%). High mortality was predicted by baseline severity of illness (median APACHE II score 23, range 21-33.25). Choice of lenient or strict PD targets (ie 100%fT >MIC or 100%fT >4XMIC) had the largest impact on probability of target attainment (PTA), whereas presence or intensity of CKRT had minimal impact on PTA.

WHAT IS NEW AND CONCLUSION

Pip-tazo overexposure may be associated with increased mortality, although this is confounded by baseline severity of illness. Achieving adequate pip-tazo exposure is essential; however, risk of harm from overexposure should be considered when choosing a PD target and dose. If lenient PD targets are desired, doses of 2250-3375 mg every 6 h are reasonable for most patients receiving CKRT. However, if a strict PD target is desired, continuous infusion (at least 9000-13500 mg per day) may be required. However, some critically ill CKRT populations may need higher or lower doses and dosing strategies should be tailored to individuals based on all available clinical data including the specific critical care setting.

Using a Validated Population Pharmacokinetic Model for Dosing Recommendations of Continuous Infusion Piperacillin for Critically Ill Adult Patients

BACKGROUND AND OBJECTIVE: Piperacillin is a broad-spectrum β-lactam antibiotic commonly prescribed in intensive care units. Many piperacillin population pharmacokinetic models have been published, but few underwent an external evaluation. External evaluation is an important process to determine a model's capability of being generalized to other hospitals. We aimed to assess the predictive performance of these models with an external validation dataset.

METHODS

Six models were evaluated with a dataset consisting of 30 critically ill patients (35 samples) receiving piperacillin by continuous infusion. Models were subject to prediction-based (bias and imprecision) and simulation-based evaluations. When a model had an acceptable evaluation, it was used for dosing simulations to evaluate the probability of target attainment.

RESULTS

Bias and imprecision ranged from - 35.7 to 295% and from 22.7 to 295%, respectively. The models of Klastrup et al. and of Udy et al. were acceptable according to our criteria and were used for dosing simulations. Simulations showed that a loading dose of 4 g followed by a maintenance dose of 16 g/24 h of piperacillin infused continuously was necessary to remain above a pharmacokinetic-pharmacodynamic target set as a minimal inhibitory concentration of 16 mg/L in 90% of patients, for a median patient with a creatinine clearance of 76 mL/min.

CONCLUSIONS

Despite the considerable variation in the predictive performance of the models with the external validation dataset, this study was able to validate two of these models and led to the elaboration of a dosing nomogram for piperacillin by continuous infusion that can be used by clinicians in intensive care units.

Experience of Vancomycin Therapeutic Drug Monitoring in Two Multidisciplinary Hospitals in Latvia

Background and Objectives: Management of infectious diseases is a huge burden to every healthcare system worldwide. Antimicrobial resistance, including antibacterial resistance, is an increasing problem worldwide; therefore, more new antibiotics are necessary to be discovered. Meanwhile, “old” antibacterial agents are still administered to fight infectious diseases caused by resistant bacteria. One of these antibacterial agents is vancomycin, which is effective in treating serious systemic infections caused by gram-positive bacteria. Thus, it is necessary to perform vancomycin concentration measurements in plasma due to its narrow therapeutic index. Various approaches are implemented for more precise therapy, including therapeutic drug monitoring (TDM) of vancomycin and with a supervision of a clinical pharmacist. The purpose of the study was to investigate if the TDM practice is improved with a local vancomycin TDM protocol applied in a hospital. The results of TDM in two multidisciplinary hospitals, one with a local TDM protocol implemented and applied and the other with no local TDM protocol implemented and applied, were compared. Materials and Methods: A retrospective study was performed in two multidisciplinary hospitals in Latvia. The data were collected for a time period of 4 years (2016−2020) in a hospital without a local TDM protocol and for a time period of 2 years (2018−2020) in a hospital with a local TDM protocol, starting with a period of time when the vancomycin TDM protocol was developed. The data about the patients included in the study were analyzed based on gender, age, body weight, and renal function. Vancomycin therapy was analyzed based on dosing schemes (vancomycin dose and dosing interval), data about loading and maintenance doses, vancomycin concentration, and details about vancomycin concentration (sampling time and concentration level). Results: Differences between the hospitals were found in terms of the initiation of vancomycin administration and concentration sampling. In the hospital with a TDM protocol compared with the hospital without a TDM protocol, more accurate initiation was found, alongside adaption of therapy (97.22% vs. 18.95%, p < 0.001), better performance of administration of a loading dose (22.73% vs. 1.29%, p < 0.01), and reaching of target concentration (55.56% vs. 35.29%, p < 0.01). Concentration sampling in the correct timeframe before the vancomycin dose and vancomycin administration did not show statistically better results in either of the hospitals (4.60% vs. 6.29%, p = 0.786). Conclusions: Better results of adequate adjustments of vancomycin therapy were achieved in the hospital with a TDM protocol. In the long term, sustainable results and regular medical professionals’ training is necessary.

Antibiotic Stewardship and Therapeutic Drug Monitoring of β-Lactam Antibiotics: Is There a Link? An Opinion Paper

PURPOSE

In critically ill patients, changes in the pharmacokinetics (PK) of β-lactams can lead to significant variations in serum concentrations, with possibly detrimental effects on outcomes. The utilization of individually calculated doses, extended infusion regimen, and therapeutic drug monitoring (TDM)-guided dose adjustments can mitigate the PK changes and help to achieve and attain an individual PK target.

METHODS

We reviewed relevant literature from 2004 to 2021 using 4 search engines (PubMed, Web of Science, Scopus, and Google Scholar). Unpublished clinical data were also examined.

RESULTS

TDM-guided, individualized dosing strategies facilitated PK target attainment and improved patient outcomes. TDM-guided therapy is a core concept of individualized dosing that increases PK target attainment and identifies possible toxic β-lactam concentrations.

CONCLUSIONS

Individualized dosing and TDM facilitate the rational use of β-lactams and are integral for antibiotic stewardship interventions in critical care, affording the optimal exposure of both pathogen and drugs, along with enhanced treatment efficacy and reduced emergence of antimicrobial resistance.

Pharmacokinetic/Pharmacodynamic Optimization of Hospital-Acquired and Ventilator-Associated Pneumonia: Challenges and Strategies

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are correlated with high mortality rates worldwide. Thus, the administration of antibiotic therapy with appropriate dosing regimen is critical. An efficient antibiotic is needed to maintain an adequate concentration at the infection site, for a sufficient period of time, to achieve the best therapeutic outcome. It can, however, be challenging for antibiotics to penetrate the pulmonary system due to the complexity of its structure. Crossing the blood alveolar barrier is a difficult process determined by multiple factors that are either drug related or infection related. Thus, the understanding of pharmacokinetics/pharmacodynamics (PK/PD) of antibiotics identifies the optimum dosing regimens to achieve drug penetration into the epithelial lining fluid at adequate therapeutic concentrations. Critically ill patients in the ICU can express augmented renal clearance (ARC), characterized by enhanced renal function, or may have renal dysfunction necessitating supportive care such as continuous renal replacement therapy (CRRT). Both ARC and CRRT can alter drug elimination, thus affecting drug concentrations. PK of critically ill patients is less clear due to the multiple variabilities associated with their condition. Therefore, conventional dosing regimens often lead to therapeutic failure. Another major hurdle faced in optimizing treatment for HAP/VAP is the reduction of the in vitro potency. Therapeutic drug monitoring (TDM), if available, may allow health care providers to personalize treatment to maximize efficacy of the drug exposures while minimizing toxicity. TDM can be of significant importance in populations whom PK are less defined and for resistant infections to achieve the best therapeutic outcome.

Are Antibiotics Appropriately Dosed in Critically Ill Patients with Augmented Renal Clearance? A Narrative Review

AIMS

Augmented renal clearance (ARC), which is commonly defined as increased renal clearance above 130 ml/min/1.73 m², is a common phenomenon among critically ill patients. The increased elimination rate of drugs through the kidneys in patients with ARC can increase the risk of treatment failure due to the exposure to subtherapeutic serum concentrations of medications and affect the optimal management of infections, length of hospital stay, and outcomes. The main goal of this review article is to summarize the recommendations for appropriate dosing of antibiotics in patients with ARC.

METHODS

This article is a narrative review of the articles that evaluated different dosing regimens of antibiotics in patients with ARC. The keywords "Augmented Renal Clearance," "Critically ill patients," "Drug dosing," "Serum concentration," "Beta-lactams," "Meropenem," "Imipenem," "Glycopeptide," "Vancomycin," "Teicoplanin," "Linezolid," "Colistin," "Aminoglycosides," "Amikacin," "Gentamycin," "Fluoroquinolones," "Ciprofloxacin," and "Levofloxacin" were searched in Scopus, Medline, PubMed, and Google Scholar databases, and pediatric, nonhuman, and non-English studies were excluded.

RESULTS

PK properties of antibiotics including lipophilicity or hydrophilicity, protein binding, the volume of distribution, and elimination rate that affect drug concentration should be considered along with PD parameters for drug dosing in critically ill patients with ARC.

CONCLUSION

This review recommends a dosing protocol for some antibiotics to help the appropriate dosing of antibiotics in ARC and decrease the risk of subtherapeutic exposure that may be observed while receiving conventional dosing regimens in critically ill patients with ARC.

Augmented Renal Clearance: What Have We Known and What Will We Do?

Augmented renal clearance (ARC) is a phenomenon of increased renal function in patients with risk factors. Sub-therapeutic drug concentrations and antibacterial exposure in ARC patients are the main reasons for clinical treatment failure. Decades of increased research have focused on these phenomena, but there are still some existing disputes and unresolved issues. This article reviews information on some important aspects of what we have known and provides suggestion on what we will do regarding ARC. In this article, we review the current research progress and its limitations, including clinical identification, special patients, risk factors, metabolism, animal models and clinical treatments, and provide some promising directions for further research in this area.

Case Report: Subtherapeutic Vancomycin and Meropenem Concentrations due to Augmented Renal Clearance in a Patient With Intracranial Infection Caused by Streptococcus intermedius

Streptococcus intermedius occasionally causes brain abscesses that can be life-threatening, requiring prompt antibiotic and neurosurgical treatment. The source is often dental, and it may spread to the eye or the brain parenchyma. We report the case of a 34-year-old man with signs of apical periodontitis, endophthalmitis, and multiple brain abscesses caused by Streptococcus intermedius. Initial treatment with meropenem and vancomycin was unsuccessful due to subtherapeutic concentrations, despite recommended dosages. Adequate concentrations could be reached only after increasing the dose of meropenem to 16 g/day and vancomycin to 1.5 g × 4. The patient exhibited high creatinine clearance consistent with augmented renal clearance, although iohexol and cystatin C clearances were normal. Plasma free vancomycin clearance followed that of creatinine. A one-day dose of trimethoprim–sulfamethoxazole led to an increase in serum creatinine and a decrease in both creatinine and urea clearances. These results indicate that increased tubular secretion of the drugs was the cause of suboptimal antibiotic treatment. The patient eventually recovered, but his left eye needed enucleation. Our case illustrates that augmented renal clearance can jeopardize the treatment of serious bacterial infections and that high doses of antibiotics are needed to achieve therapeutic concentrations in such cases. The mechanisms for regulation of kidney tubular transporters of creatinine, urea, vancomycin, and meropenem in critically ill patients are discussed.

Clinical applicability of urinary creatinine clearance for determining the initial dose of vancomycin in critically ill patients

INTRODUCTION

The purpose of this study was to evaluate the clinical applicability of urinary creatinine clearance (CrCl) for determining the initial dose of vancomycin (VCM) in critically ill patients and to assess VCM trough plasma concentration/maintenance daily dose (C/D) ratio in patients with augmented renal clearance (ARC).

METHODS

As the primary outcome measure, correlations between estimated renal function and the VCM C/D ratio were compared using the following formulas: CrCl, Cockcroft-Gault equation (eCrCl_C-G) and KineticGFR equation (KeGFR). Patients were divided into those with or without changes in renal function. The patients were further classified based on the presence or absence of ARC. The secondary outcome was the comparison of VCM C/D ratio between ARC and Non-ARC patients.

RESULTS

A total of 65 patients were enrolled for analysis. In all groups, CrCl tended to correlate better with the VCM C/D ratio than eCrCl_C-G and KeGFR. A significantly lower VCM C/D ratio was observed in patients with persistent ARC than in the Non-ARC group (0.24 versus 0.52 kg/L).

CONCLUSIONS

The clinical applicability of CrCl for the initial dosing design of VCM in critically ill patients was shown. Furthermore, the results indicated that patients with persistent ARC required a higher VCM dose than Non-ARC patients. Although our findings are limited, they have a value for further verification.

Population pharmacokinetics and dosing optimization of vancomycin in infants, children and adolescents with augmented renal clearance

Augmented renal clearance (ARC) can cause underexposure to vancomycin, thereby increasing the risk of treatment failure. Our objective was to evaluate population pharmacokinetics and optimize the dosing regimen of vancomycin in the pediatric population with ARC. Sparse pharmacokinetic sampling and therapeutic drug monitoring (TDM) data were collected from pediatric patients with ARC treated with vancomycin. A pharmacokinetic model was developed using NONMEM 7.2. The dosing regimen was optimized using Monte Carlo dose simulations. A total of 242 vancomycin serum concentrations from 113 patients (age range 0.4 to 14.9 years, 49 females and 64 males) were available. Mean vancomycin dose was 58.8 mg/kg/day (13.6 mg/kg/dose), and mean vancomycin serum trough concentration was 6.5 mg/L. A one-compartment pharmacokinetic model with first order elimination was developed. Body weight and age were the most significant and positive covariates for clearance and volume of distribution. To the pediatric population with ARC, the current recommended vancomycin dose of 60 mg/kg/day was associated with a high risk of underdosing. To reach the target AUC/MIC of 400-700 in these pediatric patients, the vancomycin dose should be increased to 75 mg/kg/day for infants and children between 1 month and 12 years of age, and 70 mg/kg/day for adolescents between 12 and 18 years of age. In conclusion, a one-compartment pharmacokinetic model with first-order elimination was established with body weight and age as significant covariates. An optimal dosing regimen was developed in pediatric patients with ARC aged 1 month -18 years.

Pharmacokinetics of Non-β-Lactam β-Lactamase Inhibitors

The growing emergence of drug-resistant bacterial strains is an issue to treat severe infections, and many efforts have identified new pharmacological agents. The inhibitors of β-lactamases (BLI) have gained a prominent role in the safeguard of beta-lactams. In the last years, new β-lactam-BLI combinations have been registered or are still under clinical evaluation, demonstrating their effectiveness to treat complicated infections. It is also noteworthy that the pharmacokinetics of BLIs partly matches that of β-lactams companions, meaning that some clinical situations, as well as renal impairment and renal replacement therapies, may alter the disposition of both drugs. Common pharmacokinetic characteristics, linear pharmacokinetics across a wide range of doses, and known pharmacokinetic/pharmacodynamic parameters may guide modifications of dosing regimens for both β-lactams and BLIs. However, comorbidities (i.e., burns, diabetes, cancer) and severe changes in individual pathological conditions (i.e., acute renal impairment, sepsis) could make dose adaptation difficult, because the impact of those factors on BLI pharmacokinetics is partly known. Therapeutic drug monitoring protocols may overcome those issues and offer strategies to personalize drug doses in the intensive care setting. Further prospective clinical trials are warranted to improve the use of BLIs and their β-lactam companions in severe and complicated infections.

The Development of a Juvenile Porcine Augmented Renal Clearance Model Through Continuous Infusion of Lipopolysaccharides: An Exploratory Study

Augmented renal clearance (ARC) as observed in the critically ill (pediatric) population can have a major impact on the pharmacokinetics and posology of renally excreted drugs. Although sepsis has been described as a major trigger in the development of ARC in human critically ill patients, mechanistic insights on ARC are currently lacking. An appropriate ARC animal model could contribute to reveal these underlying mechanisms. In this exploratory study, a state of ARC was induced in 8-week-old piglets. Conscious piglets were continuously infused over 36 h with lipopolysaccharides (LPS) from Escherichia coli (O111:B4) to induce sepsis and subsequently trigger ARC. To study the dose-dependent effect of LPS on the renal function, three different doses (0.75, 2.0, 5.0 μg/kg/h) were administered (two ♂ piglets/dose, one sham piglet), in combination with fluid administration (0.9% NaCl) at 6 ml/kg/h. Single boluses of renal markers, i.e., creatinine [40 mg/kg body weight (BW)], iohexol (64.7 mg/kg BW), and para-aminohippuric acid (PAH, 10 mg/kg BW) were administered intravenously to evaluate the effect of LPS on the renal function. Clinical parameters were monitored periodically. Blood sampling was performed to determine the effect on hematology, neutrophil gelatinase-associated lipocalin, and prostaglandin E₂ plasma levels. All piglets that were continuously infused with LPS displayed an elevated body temperature, heart rhythm, and respiratory rate ~1-3 h after start of the infusion. After infusion, considerably higher total body clearances of iohexol, creatinine, and PAH were observed, independent of the administration of LPS and/or its dose. Since also the sham piglet, receiving no LPS, demonstrated a comparable increase in renal function, the contribution of fluid administration to the development of ARC should be further evaluated.

Piperacillin-Tazobactam in Intensive Care Units: A Review of Population Pharmacokinetic Analyses

Piperacillin-tazobactam is a potent β-lactam/β-lactamase inhibitor antibiotic commonly prescribed in the intensive care unit setting. Admitted patients often show large variability in treatment response due to multiple pathophysiological changes present in this population that alter the drug's pharmacokinetics. This review summarizes the population pharmacokinetic models developed for piperacillin-tazobactam and provides comprehensive data on current dosing strategies while identifying significant covariates in critically ill patients. A literature search on the PubMed database was conducted, from its inception to July 2020. Relevant articles were retained if they met the defined inclusion/exclusion criteria. A total of ten studies, published between 2009 and 2020, were eligible. One- and two-compartment models were used in two and eight studies, respectively. The lowest estimated piperacillin clearance value was 3.12 L/h, and the highest value was 19.9 L/h. The estimations for volume of distribution varied between 11.2 and 41.2 L. Tazobactam clearance values ranged between 5.1 and 6.78 L/h, and tazobactam volume of distribution values ranged between 17.5 and 76.1 L. The most frequent covariates were creatinine clearance and body weight, each present in four studies. Almost all studies used an exponential approach for the interindividual variability. The highest variability was observed in piperacillin central volume of distribution, at a value of 75.0%. Simulations showed that continuous or extended infusion methods performed better than intermittent administration to achieve appropriate pharmacodynamic targets. This review synthesizes important pharmacokinetic elements for piperacillin-tazobactam in an intensive care unit setting. This will help clinicians better understand changes in the drug's pharmacokinetic parameters in this specific population.

Issues in antibiotic therapy for hospital-acquired and ventilator-associated pneumonia: emerging concepts to improve outcomes

Introduction:Ventilator-associated pneumonia (VAP) and hospital-acquired pneumonia (HAP) result in significant morbidity and mortality. The emergence of multi-drug resistant organisms has complicated the matter, as many of these pathogens now represent key causes of VAP and HAP. While anumber of new medications have been approved, acomprehensive appreciation of pharmacokinetic and pharmacodynamic principles, which, are often neglected, is key to effective treatment.Areas covered: The authors discuss the central pharmacokinetic and pharmacodynamic principles underlying antibiotic utilization, especially as they pertain to the treatment of VAP and HAP. They further address the concept of and implications of augmented renal clearance for the patient with nosocomial pneumonia. Finally, the authors review the evolving data on colistin and inhaled antibiotics in the management of pneumonia.Expert opinion: An enhanced understanding of the pharmacokinetic and pharmacodynamic principles along with insight into the concept of augmented renal clearance can help guide drug development and improve the way we currently dose and deliver most antibiotics. There is now mounting data on the limited efficacy and substantial nephrotoxicity of colistin, which makes it difficult to justify its continued use. While the concept of inhaled antibiotics is enticing, we lack conclusive data proving the efficacy of this paradigm.

Augmented Renal Clearance in a Case of Sepsis Leading to Vancomycin Failure Despite Increasing Dose As per the Estimated Glomerular Filtration Rate

Augmented renal clearance (ARC) is a unique clinical scenario observed in critically ill patients. We present a case of a 30-year-old male with sepsis secondary to methicillin-resistant Staphylococcus aureus (MRSA) bacteremia treated with vancomycin. ARC was observed in the patient with a maximum estimated glomerular filtration rate (eGFR) of 161.9 ml/min/1.73 m², and therapeutic drug monitoring was used to adjust the vancomycin dosage. Despite the maximal recommended dose of vancomycin, the therapeutic vancomycin level was not achieved, leading to treatment failure and subsequent mortality. Our case report suggests the necessity of other strategies, such as early dose adjustment of vancomycin based on vancomycin clearance and continuous vancomycin infusion, not merely conventional adjustment based on eGFR and vancomycin levels.

From Therapeutic Drug Monitoring to Model-Informed Precision Dosing for Antibiotics

Therapeutic drug monitoring (TDM) and model-informed precision dosing (MIPD) have evolved as important tools to inform rational dosing of antibiotics in individual patients with infections. In particular, critically ill patients display altered, highly variable pharmacokinetics and often suffer from infections caused by less susceptible bacteria. Consequently, TDM has been used to individualize dosing in this patient group for many years. More recently, there has been increasing research on the use of MIPD software to streamline the TDM process, which can increase the flexibility and precision of dose individualization but also requires adequate model validation and re-evaluation of existing workflows. In parallel, new minimally invasive and noninvasive technologies such as microneedle-based sensors are being developed, which-together with MIPD software-have the potential to revolutionize how patients are dosed with antibiotics. Nonetheless, carefully designed clinical trials to evaluate the benefit of TDM and MIPD approaches are still sparse, but are critically needed to justify the implementation of TDM and MIPD in clinical practice. The present review summarizes the clinical pharmacology of antibiotics, conventional TDM and MIPD approaches, and evidence of the value of TDM/MIPD for aminoglycosides, beta-lactams, glycopeptides, and linezolid, for which precision dosing approaches have been recommended.

Antibiotic therapy in sepsis: No next time for a second chance!

WHAT IS KNOWN AND OBJECTIVE

Sepsis is a life-threatening organ dysfunction associated with a high rate of morbidity and mortality. Appropriate antibiotic therapy remains the cornerstone of sepsis and septic shock management.

COMMENT

Although the early initiation of antimicrobial agents in the treatment of sepsis is widely acknowledged, the selection and adjustment to optimal dosage can be equally important. Since significant pathophysiological changes in the critically ill patients lead to altered pharmacokinetics of antibiotics, early consideration of pharmacokinetic/pharmacodynamic (PK/PD) properties is necessary for optimal antibiotic dosing in sepsis and should be integrated in practice.

WHAT IS NEW AND CONCLUSION

Where possible, an individualized antibiotic dosing approach through the application of therapeutic drug monitoring (TDM) service should replace the conventional dosing in critically ill patients with sepsis. Finally, antimicrobial stewardship can help improve clinical outcomes.