Development of a dosing nomogram for continuous-infusion meropenem in critically ill patients based on a validated population pharmacokinetic model

Impact of continuous-infusion meropenem degradation and infusion bag changes on bacterial killing of Pseudomonas aeruginosa based on model-informed translation

BACKGROUND

Continuous infusion of meropenem has been proposed to increase target attainment in critically ill patients, although stability might limit its practical use. This study investigated the impact of meropenem degradation and infusion bag changes on the concentration-time profiles and bacterial growth and killing of P. aeruginosa given different continuous-infusion solutions.

METHODS

A semi-mechanistic pharmacokinetic-pharmacodynamic (PK-PD) model quantifying meropenem concentrations (CMEM) and bacterial counts of a resistant P. aeruginosa strain (ARU552, MIC = 16 mg/L) over 24 h was used to translate in vitro antibiotic effects to patients with severe infections. Concentration-dependent drug degradation of saline infusion solutions was considered using an additional compartment in the population PK model. CMEM, fT>MIC (time that concentrations exceed the MIC) and total bacterial load (BTOT) after 24 h were simulated for different scenarios (n = 144), considering low- and high-dose regimens (3000/6000 mg/day±loading dose), clinically relevant infusion solutions (20/40/50 mg/mL), different intervals of infusion bag changes (every 8/24 h, q8/24 h), and varied renal function (creatinine clearance 40/80/120 mL/min) and MIC values (8/16 mg/L).

RESULTS

Highest deviations between changing infusion bags q8h and q24h were observed for 50 mg/mL solutions and scenarios with CMEM_24h close to the MIC, with differences (Δ) in CMEM_24h up to 4.9 mg/L, ΔfT>MIC≤65.7%, and ΔBTOT_24h≤1.1 log10 CFU/mL, thus affecting conclusions on whether bacteriostasis was reached.

CONCLUSIONS

In summary, this study indicated that for continuous infusion of meropenem, eight-hourly infusion bag changes improved PK/PD target attainment and might be beneficial particularly for high meropenem concentrations of saline infusion solutions and for plasma concentrations in close proximity to the MIC.

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

INTRODUCTION

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

AREA COVERED

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

EXPERT OPINION

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

Systematic review of room temperature stability of key beta-lactam antibiotics for extended infusions in inpatient settings

BACKGROUND

Extended infusion (EI) of beta-lactam antibiotics may offer clinical benefits aligned with improved probability of target attainment for critical pharmacokinetic/pharmacodynamic parameters that correlate with efficacy. There is much research interest in prolonged and continuous infusions (collectively, extended infusions) of beta-lactams to improve patient outcomes, particularly in critically ill patients in intensive care. While definitive clinical trial data demonstrating beneficial outcomes is awaited, there has been limited focus on the stability of the agents given by EI, which may be an equally critical parameter. EI may allow for savings in nursing time due to reduced need for drug reconstitution. We set out to examine the data for stability for EI at room temperature, consistent with the requirements of 'A Standard Protocol for Deriving and Assessment of Stability- Part 1 Aseptic Preparation (Small Molecules)', which allows a 5% loss of active pharmaceutical ingredient (API) applicable for those territories that use the British Pharmacopoeia also for a 10% loss applicable in much of rest of the world.

METHODS

Searches using preferred reporting items for systematic reviews and meta-analyses (PRISMA) principles for stability data on freshly prepared beta-lactam antimicrobials for extended administration at room temperature (at or above 23°C) were conducted in November 2021 and updated in December 2022.

RESULTS

We found data to support the extension of the shelf life of 12 key beta-lactam antibiotics once reconstituted (aztreonam, amoxicillin, benzylpenicillin, flucloxacillin, piperacillin/tazobactam, cefazolin, cefmetazole, ceftaroline, ceftazidime, ceftriaxone, imipenem and meropenem) compliant with the NHS protocol, and data for five other agents (ticarcillin, cefepime, cefiderocol, cefoxitin and doripenem) which would be acceptable in regions outside the UK beyond that listed in the Summary of Product Characteristics.This review has not been registered under PROSPERO.

Does Cytokine-Release Syndrome Induced by CAR T-Cell Treatment Have an Impact on the Pharmacokinetics of Meropenem and Piperacillin/Tazobactam in Patients with Hematological Malignancies? Findings from an Observational Case-Control Study

Chimeric antigen receptor (CAR) T-cell therapy is a promising approach for some relapse/refractory hematological B-cell malignancies; however, in most patients, cytokine release syndrome (CRS) may occur. CRS is associated with acute kidney injury (AKI) that may affect the pharmacokinetics of some beta-lactams. The aim of this study was to assess whether the pharmacokinetics of meropenem and piperacillin may be affected by CAR T-cell treatment. The study included CAR T-cell treated patients (cases) and oncohematological patients (controls), who were administered 24-h continuous infusion (CI) meropenem or piperacillin/tazobactam, optimized by therapeutic drug monitoring, over a 2-year period. Patient data were retrospectively retrieved and matched on a 1:2 ratio. Beta-lactam clearance (CL) was calculated as CL = daily dose/infusion rate. A total of 38 cases (of whom 14 and 24 were treated with meropenem and piperacillin/tazobactam, respectively) was matched with 76 controls. CRS occurred in 85.7% (12/14) and 95.8% (23/24) of patients treated with meropenem and piperacillin/tazobactam, respectively. CRS-induced AKI was observed in only 1 patient. CL did not differ between cases and controls for both meropenem (11.1 vs. 11.7 L/h, p = 0.835) and piperacillin (14.0 vs. 10.4 L/h, p = 0.074). Our findings suggest that 24-h CI meropenem and piperacillin dosages should not be reduced a priori in CAR T-cell patients experiencing CRS.

Meropenem Model-Informed Precision Dosing in the Treatment of Critically Ill Patients: Can We Use It?

The number of pharmacokinetic (PK) models of meropenem is increasing. However, the daily role of these PK models in the clinic remains unclear, especially for critically ill patients. Therefore, we evaluated the published meropenem models on real-world ICU data to assess their suitability for use in clinical practice. All models were built in NONMEM and evaluated using prediction and simulation-based diagnostics for the ability to predict the subsequent meropenem concentrations without plasma concentrations (a priori), and with plasma concentrations (a posteriori), for use in therapeutic drug monitoring (TDM). Eighteen PopPK models were included for evaluation. The a priori fit of the models, without the use of plasma concentrations, was poor, with a prediction error (PE)% of the interquartile range (IQR) exceeding the ±30% threshold. The fit improved when one to three concentrations were used to improve model predictions for TDM purposes. Two models were in the acceptable range with an IQR PE% within ±30%, when two or three concentrations were used. The role of PK models to determine the starting dose of meropenem in this population seems limited. However, certain models might be suitable for TDM-based dose adjustment using two to three plasma concentrations.

Development and validation of a dosing nomogram for continuous infusion cloxacillin in infective endocarditis

BACKGROUND

Cloxacillin is the first-line treatment for methicillin-susceptible staphylococcal infective endocarditis (IE). The recommended dose is 12 g per day regardless of the patient characteristics, despite the importance of renal function on its pharmacokinetics.

OBJECTIVES

We sought to build a population pharmacokinetics model of continuous infusion cloxacillin in IE patients to evaluate the influence of multiple covariates and then develop a nomogram based on significant covariates for individual adaptation.

PATIENTS AND METHODS

We included patients of a local IE cohort who were treated with cloxacillin administered by continuous infusion, excluding those who received intermittent or continuous dialysis, extracorporeal membrane oxygenation or extracorporeal circulation. The population pharmacokinetic analysis was performed using Pmetrics. The influence of weight, ideal weight, height, body mass index, body surface area, glomerular filtration rate (GFR) calculated with the Chronic Kidney Disease Epidemiology Collaboration formula (both expressed in mL/min/1.73 m² and in mL/min) and serum protein level on cloxacillin pharmacokinetics was assessed. Accounting for relevant covariates, a dosing nomogram was developed to determine the optimal daily dose required to achieve a steady-state plasma concentration range of 20-50 mg/L with a probability ≥0.9.

RESULTS

A total of 114 patients (331 plasma concentrations) were included. A one-compartment model including GFR expressed in mL/min as a covariate was chosen. Using the nomogram, achieving the cloxacillin concentration target requires a daily dose ranging from 3.5 to 13.1 g for a GFR ranging from 20 to 125 mL/min.

CONCLUSIONS

This work provided a practical tool for cloxacillin dose adjustment in IE according to renal function.

Evaluation of Empirical Dosing Regimens for Meropenem in Intensive Care Unit Patients Using Population Pharmacokinetic Modeling and Target Attainment Analysis

In the present study, population pharmacokinetic (PK) analysis was performed based on meropenem data from a prospective study conducted in 114 critically ill patients with a wide range of renal functions and various disease conditions. The final model was a one-compartment model with linear elimination, with creatinine clearance and continuous renal replacement therapy affecting clearance, and total bodyweight impacting the volume of distribution. Our model is a valuable addition to the existing meropenem population PK models, and it could be particularly useful during implementation of a therapeutic drug monitoring program combined with Bayesian forecasting. Based on the final model developed, comprehensive Monte Carlo simulations were performed to evaluate the probability of target attainment (PTA) of 16 different dosing regimens. Simulation results showed that 2 g administered every 8 h with 3-h prolonged infusion (PI) and 4 g/day by continuous infusion (CI) appear to be two empirical dosing regimens that are superior to many other regimens when both target attainment and potential toxicity are considered and renal function information is not available. Following a daily CI dose of 6 g or higher, more than 30% of the population with a creatinine clearance of <60 mL/min is predicted to have neurotoxicity. With the availability of institution- and/or unit-specific meropenem susceptibility patterns, as well as an individual patient's renal function, our PTA results may represent useful references for physicians to make dosing decisions.

Developmental Population Pharmacokinetics-Pharmacodynamics of Meropenem in Chinese Neonates and Young Infants: Dosing Recommendations for Late-Onset Sepsis

The pharmacokinetic (PK) studies of meropenem in Chinese newborns with late-onset sepsis (LOS) are still lacking. Causative pathogens of LOS and their susceptibility patterns in China differ from the data abroad. We, therefore, conducted a developmental population pharmacokinetic−pharmacodynamic analysis in Chinese newborns with the goal to optimize meropenem dosing regimens for LOS therapy. An opportunistic sampling strategy was used to collect meropenem samples, followed by model building and validation. A Monte Carlo simulation was performed to show the probability of target attainment (PTA) for various dosages. The information from 78 newborns (postmenstrual age: 27.4−46.1 weeks) was compiled and had a good fit to a 1-compartment model that had first order elimination. The median (range) values of estimated weight−normalized volume of distribution (V)and clearance (CL) were 0.60 (0.51−0.69) L/kg and 0.16 (0.04−0.51) L/h/kg, respectively. Covariate analysis revealed that postnatal age (PNA), gestational age (GA) and current weight (CW) were the most important factors in describing meropenem PK. Simulation results showed for LOS with a minimal inhibitory concentration (MIC) of 8 mg/L, the doses of 30 mg/kg 3 times daily (TID) as a 1-h infusion for newborns with GA ≤ 37 weeks and 40 mg/kg TID as a 3-h infusion for those with GA > 37 weeks were optimal, with PTA of 71.71% and 75.08%, respectively. In conclusion, we proposed an evidence-based dosing regimen of meropenem for LOS in Chinese newborns by using the population pharmacokinetic−pharmacodynamic analysis, based on domestic common pathogens and their susceptibility patterns.

Population Pharmacokinetics/Pharmacodynamics and Clinical Outcomes of Meropenem in Critically Ill Patients

Several pathophysiological changes can alter meropenem pharmacokinetics in critically ill patients, thereby increasing the risk of subtherapeutic concentrations and affecting therapeutic outcomes. This study aimed to characterize the population pharmacokinetic (PPK) parameters of meropenem, evaluate the relationship between the pharmacokinetic/pharmacodynamic index of meropenem and treatment outcomes, and evaluate the different dosage regimens that can achieve 40%, 75%, and 100% of the dosing interval for which the free plasma concentrations remain above the MIC of the pathogens (fT_>MIC) targets. Critically ill adult patients treated with meropenem were recruited for this study. Five blood samples were collected from each patient. PPK models were developed using a nonlinear mixed-effects modeling approach, and the final model was subsequently used for Monte Carlo simulations to determine the optimal dosage regimens. A total of 247 concentrations from 52 patients were available for analysis. The two-compartment model with linear elimination adequately described the data. The mean PPK parameters were clearance (CL) of 4.8 L/h, central volume of distribution (V_C) of 11.4 L, peripheral volume of distribution (V_P) of 14.6 L, and intercompartment clearance of 10.5 L/h. Creatinine clearance was a significant covariate affecting CL, while serum albumin level and shock status were factors influencing V_C and V_P, respectively. Although 75% of the drug-resistant infection patients had fT_>MIC values of >40%, approximately 83% of them did not survive the infection. Therefore, 40% fT_>MIC might not be sufficient for critically ill patients, and a higher target, such as 75 to 100% fT_>MIC, should be considered for optimizing therapy. A 75% fT_>MIC could be reached using approved doses administered via a 3-h infusion.

Evaluation of a Meropenem and Piperacillin Monitoring Program in Intensive Care Unit Patients Calls for the Regular Assessment of Empirical Targets and Easy-to-Use Dosing Decision Tools

The drug concentrations targeted in meropenem and piperacillin/tazobactam therapy also depend on the susceptibility of the pathogen. Yet, the pathogen is often unknown, and antibiotic therapy is guided by empirical targets. To reliably achieve the targeted concentrations, dosing needs to be adjusted for renal function. We aimed to evaluate a meropenem and piperacillin/tazobactam monitoring program in intensive care unit (ICU) patients by assessing (i) the adequacy of locally selected empirical targets, (ii) if dosing is adequately adjusted for renal function and individual target, and (iii) if dosing is adjusted in target attainment (TA) failure. In a prospective, observational clinical trial of drug concentrations, relevant patient characteristics and microbiological data (pathogen, minimum inhibitory concentration (MIC)) for patients receiving meropenem or piperacillin/tazobactam treatment were collected. If the MIC value was available, a target range of 1–5 × MIC was selected for minimum drug concentrations of both drugs. If the MIC value was not available, 8–40 mg/L and 16–80 mg/L were selected as empirical target ranges for meropenem and piperacillin, respectively. A total of 356 meropenem and 216 piperacillin samples were collected from 108 and 96 ICU patients, respectively. The vast majority of observed MIC values was lower than the empirical target (meropenem: 90.0%, piperacillin: 93.9%), suggesting empirical target value reductions. TA was found to be low (meropenem: 35.7%, piperacillin 50.5%) with the lowest TA for severely impaired renal function (meropenem: 13.9%, piperacillin: 29.2%), and observed drug concentrations did not significantly differ between patients with different targets, indicating dosing was not adequately adjusted for renal function or target. Dosing adjustments were rare for both drugs (meropenem: 6.13%, piperacillin: 4.78%) and for meropenem irrespective of TA, revealing that concentration monitoring alone was insufficient to guide dosing adjustment. Empirical targets should regularly be assessed and adjusted based on local susceptibility data. To improve TA, scientific knowledge should be translated into easy-to-use dosing strategies guiding antibiotic dosing.

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.

Dried Plasma Spot Based LC-MS/MS Method for Monitoring of Meropenem in the Blood of Treated Patients

Meropenem (MER) is widely used to treat complicated and serious infections. Therapeutic drug monitoring (TDM) provides a valid clinical tool to avoid suboptimal concentrations and dose−related adverse reactions. However, TDM seems to face challenges since the limited stability of MER in plasma makes transport difficult between clinics and laboratories. Dried plasma spot (DPS) sampling is an attractive but underutilized method for TDM that has the desired features of easy collection, storage, and transport, and overcomes known hematocrit (HCT) issues in dried blood spot (DBS) analysis. This study was designed to investigate a DPS−based liquid chromatography−tandem mass spectrometry (LC−MS/MS) method for quantification of MER. The method was developed and validated for DPS and wet plasma samples. Calibration curves were linear (R2 > 0.995) over the concentration range of 0.5−50 µg/mL. Overall accuracy and precision did not exceed 15% and no significant matrix effect was observed. MER has been more stable in DPS than in wet plasma samples. A comparison of DPS and wet plasma concentrations was assessed in 32 patients treated with MER. The results showed that there was no significant difference between the two methods. So the DPS method developed in this study is appropriate and practical for the monitor of MER in the daily clinical laboratory practice.

A sensitive and selective HPLC-MS3 method for therapeutic drug monitoring of meropenem and its validation by comparison with HPLC-MS2 methods

Meropenem, a representative β-lactam antibiotic, is widely used to treat complicated and serious infections. Therefore, it is a great significance to monitor the plasma drug concentration for individualized antimicrobial therapy. This study first describes the development and validation of high performance liquid chromatography-tandem mass spectrometry cubed method for monitoring meropenem in human plasma. Protein precipitation with methanol and a chromatographic analysis time of 7 min make this method is simple and high-throughput. Meropenem was extracted from human plasma with recoveries greater than 94.1%. Calibration curves were linear (R² >0.995) in the concentration range of 0.5-50 μg/mL. Overall accuracy and precision did not exceed 8.0% as well as no significant matrix effect was observed. The novelty of this method is that the triple-stage MS technology improves the selectivity and sensitivity. A comparison of the presented method and traditional liquid chromatography-tandem mass spectrometry method was assessed in 44 patients treated with meropenem and Passing-Bablok regression coefficients and Bland-Altman plots showed that no significant difference between the two methods. So the triple-stage MS method developed in this study is appropriate and practical for the monitor of meropenem in the daily clinical laboratory practice. This article is protected by copyright. All rights reserved.

Biomarkers Predicting Tissue Pharmacokinetics of Antimicrobials in Sepsis: A Review

The pathophysiology of sepsis alters drug pharmacokinetics, resulting in inadequate drug exposure and target-site concentration. Suboptimal exposure leads to treatment failure and the development of antimicrobial resistance. Therefore, we seek to optimize antimicrobial therapy in sepsis by selecting the right drug and the correct dosage. A prerequisite for achieving this goal is characterization and understanding of the mechanisms of pharmacokinetic alterations. However, most infections take place not in blood but in different body compartments. Since tissue pharmacokinetic assessment is not feasible in daily practice, we need to tailor antibiotic treatment according to the specific patient’s pathophysiological processes. The complex pathophysiology of sepsis and the ineffectiveness of current targeted therapies suggest that treatments guided by biomarkers predicting target-site concentration could provide a new therapeutic strategy. Inflammation, endothelial and coagulation activation markers, and blood flow parameters might be indicators of impaired tissue distribution. Moreover, hepatic and renal dysfunction biomarkers can predict not only drug metabolism and clearance but also drug distribution. Identification of the right biomarkers can direct drug dosing and provide timely feedback on its effectiveness. Therefore, this might decrease antibiotic resistance and the mortality of critically ill patients. This article fills the literature gap by characterizing patient biomarkers that might be used to predict unbound plasma-to-tissue drug distribution in critically ill patients. Although all biomarkers must be clinically evaluated with the ultimate goal of combining them in a clinically feasible scoring system, we support the concept that the appropriate biomarkers could be used to direct targeted antibiotic dosing.

A dosing nomograph for cerebrospinal fluid penetration of meropenem applied by continuous infusion in patients with nosocomial ventriculitis

OBJECTIVES

In difficult to treat infections such as nosocomial ventriculitis, meropenem exposure in the infected compartment is often uncertain but crucial for antibacterial effects. The aim of this study was to investigate the cerebrospinal fluid (CSF) penetration of meropenem in patients with nosocomial ventriculitis and to derive a nomograph to predict effective meropenem doses as a function of clinical parameters.

METHODS

Retrospective patient data including meropenem serum and CSF levels, as well as CSF inflammation markers were analysed using NONMEM® to assess the general pharmacokinetics and CSF penetration. Monte Carlo simulations (MCS) were used to evaluate different meropenem dosing regimens. Probability of target attainment (PTA) in CSF was assessed and a nomograph to achieve a target concentration of 4 mg/L was developed.

RESULTS

A one-compartment model with meropenem clearance dependent on the estimated glomerular filtration rate (CKD-EPI eGFR, p< 5 e-10) best described meropenem serum pharmacokinetics of 51 critically ill patients. CSF penetration ratio was correlated with the amount of protein in CSF (p< 1 e-8), with higher CSF protein levels accounting for higher penetration ratios. Preserved renal function (CKD-EPI GFR> 50 ml/min/1.73 m²) as well as low CSF protein levels (<500 mg/L) resulted in 80 % PTA (100 %fT>_2xMIC) for a meropenem dose of 6 g/24 h.

CONCLUSIONS

High interindividual variability in meropenem CSF concentration was observed in patients with nosocomial ventriculitis. A nomograph to predict the daily meropenem dose required for target attainment for a given eGFR and CSF protein count was developed.

Investigation of pharmacokinetic and clinical outcomes of various meropenem regimens in patients with ventilator-associated pneumonia and augmented renal clearance

INTRODUCTION

Augmented renal clearance (ARC) defined as creatinine clearance (Clcr) above 130 mL/min/1.73m² may lead to suboptimal antibacterial treatment. The aim of this study was to determine a strategy for meropenem administration to achieve both pharmacodynamic-pharmacokinetic (PK-PD) target (50%fT > MIC) and better clinical outcomes in patients with VAP and ARC.

MATERIALS AND METHODS

In this randomized clinical trial, patients with VAP and high risk for ARC were recruited. An 8-h urine collection was performed on the 1st, 3rd, and 5th days of study to measure Clcr. Included patients were divided into three groups: (1) 1 g meropenem, 3-h infusion, (2) 2 g meropenem, 3-h infusion, (3) 1 g meropenem, 6-h infusion. On the 2nd, 3rd, and 5th days of treatment, peak and trough blood samples were collected to undergo HPLC assay. MICs were assessed using microdilution method. Patients were also clinically monitored for 14 days.

RESULTS

Forty-five patients were included. Group 3 showed significanty higher rate of patients achieving fT > MIC > 50% (100% for group 3 versus 40% for group 2 and 13% for group 1; p = 0.0001). Mean fT > MIC% was significantly higher in group 3 (78.77 ± 5.87 for group 3 versus 49.6 ± 7.38 for group 2 and 43.2 ± 7.98 for group 1; p = 0.0001). Statistical analysis showed no significant differences among groups regarding clinical improvement.

CONCLUSION

According to the findings of this trial, prolonged meropenem infusion is an appropriate strategy compared to dose elevation among ARC patients.

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.

Meropenem Target Attainment and Population Pharmacokinetics in Critically Ill Septic Patients with Preserved or Increased Renal Function

Purpose

Critically ill patients with preserved or increased renal function have been shown to be at risk of underexposure to meropenem. Although many meropenem population pharmacokinetic (PK) models have been published, there is no large prospective population PK study with rich sampling focusing on patients most at risk of suboptimal pharmacokinetic/pharmacodynamic (PK/PD) target attainment. Therefore, the aim of the present study was to evaluate PK/PD target attainment and to perform a thorough covariate screening using population PK modelling of meropenem in septic patients with preserved or increased renal function.

Patients and Methods

A single-centre prospective observational PK study was performed in the intensive care unit (ICU) of the University Hospitals Leuven. Patients with severe sepsis or septic shock and treated with meropenem in the ICU were screened for inclusion. Patients were excluded if they received renal replacement therapy or had an estimated glomerular filtration rate according to the Chronic Kidney Disease Epidemiology collaboration equation <70 mL/min/1.73m² on the day of PK sampling. Successful PK/PD target attainment was defined as an unbound meropenem trough concentration above 2 mg/L or 8 mg/L. Population PK modelling was performed with NONMEM7.4.

Results

In total, 58 patients were included, contributing 345 plasma samples over 70 dosing intervals. The 2 mg/L and 8 mg/L targets were successfully attained in 46% and 11% of all dosing intervals, respectively. A two-compartment population PK model with linear elimination and interindividual variability on clearance best described meropenem PK. The estimated creatinine clearance according to the Cockcroft-Gault equation was the only covariate retained during population PK analysis.

Conclusion

This study provided detailed insight into meropenem PK in critically ill patients with preserved or increased renal function. We observed poor PK/PD target attainment, for which renal function was the only significant covariate.

Trial Registration

This study is registered at ClinicalTrials.gov (NCT03560557).

Identification of factors affecting meropenem pharmacokinetics in critically ill patients: Impact of inflammation on clearance

INTRODUCTION

The purpose of this study was to explore factors influencing meropenem pharmacokinetics (PKs) in critically ill patients by developing a population PK model and to determine the optimal dosing strategy.

METHODS

This prospective observational study involved 12 critically ill patients admitted to the intensive care unit and treated with meropenem 1 g infused over 1 h every 8 h. Blood samples were collected on days 1, 2, and 5 immediately prior to dosing, and at 1, 2, 4, and 6 h after the start of infusion. Population PK parameters were estimated using nonlinear mixed-effects model software.

RESULTS

Meropenem PK was adequately described using a two-compartment model. Typical values of total and inter-compartmental clearance were 9.30 L/h and 9.70 L/h, respectively, and the central and peripheral compartment volumes of distribution were 12.61 L and 7.80 L, respectively. C-reactive protein (CRP) was identified as significant covariate affecting total meropenem clearance. The probability of target attainment (PTA) predicted by Monte Carlo simulations varied according to the patients' CRP. The PTA of 100% time above the minimum inhibitory concentration ≤2 mg/L for bacteria was achieved after a dose of 1 and 2 g infused over 4 h every 8 h in patients with CRP of 30 and 5 mg/dL, respectively.

CONCLUSION

The findings of this study suggest that CRP might be helpful in managing meropenem dosing in critically ill patients. Higher doses and extended infusion may be required to achieve optimal pharmacodynamic targets.

Impact of Maximizing Css/MIC Ratio on Efficacy of Continuous Infusion Meropenem Against Documented Gram-Negative Infections in Critically Ill Patients and Population Pharmacokinetic/Pharmacodynamic Analysis to Support Treatment Optimization

Introduction: optimal treatment of Gram-negative infections in critically ill patients is challenged by changing pathophysiological conditions, reduced antimicrobial susceptibility and limited therapeutic options. The aim of this study was to assess the impact of maximizing Css/MIC ratio on efficacy of continuous infusion (CI) meropenem in treating documented Gram-negative infections in critically ill patients and to perform a population pharmacokinetic/pharmacodynamic analysis to support treatment optimization.

Materials and Methods: Classification and regression tree (CART) analysis was used to identify whether a cutoff of steady-state meropenem concentration (Css)-to-minimum inhibitory concentration (MIC) (Css/MIC) ratio correlated with favorable clinical outcome. A non-parametric approach with Pmetrics was used for pharmacokinetic analysis and covariate evaluation. The probability of target attainment (PTA) of the identified Css/MIC ratio was calculated by means of Monte Carlo simulations. Cumulative fraction of response (CFRs) were calculated against common Enterobacterales, P. aeruginosa and A. baumannii as well.

Results: a total of 74 patients with 183 meropenem Css were included. CART analysis identified a Css/MIC ratio ≥4.63 as cutoff value significantly associated with favorable clinical outcomes. Multivariate regression analysis confirmed the association [OR (95%CI): 20.440 (2.063–202.522); p < 0.01]. Creatinine clearance (CL_CR) was the only covariate associated with meropenem clearance. Monte Carlo simulations showed that, across different classes of renal function, dosages of meropenem ranging between 0.5 and 2 g q6h over 6 h (namely by CI) may grant PTAs of Css/MIC ratios ≥4.63 against susceptible pathogens with an MIC up to the EUCAST clinical breakpoint of 2 mg/L. The CFRs achievable with these dosages were very high (>90%) against Enterobacterales across all the classes of renal function and against P. aeruginosa among patients with CL_CR < 30 ml/min/1.73 m², and quite lower against A. baumannii.

Discussion: our findings suggest that Css/MIC ratio ≥4.63 may be considered the pharmacodynamic target useful at maximizing the efficacy of CI meropenem in the treatment of Gram-negative infections in critically ill patients. Dosages ranging between 0.5 g q6h and 2 g q6h by CI may maximize the probability of favorable clinical outcome against meropenem-susceptible Gram-negative pathogens among critically ill patients having different degrees of renal function.

Comparative Plasma and Interstitial Tissue Fluid Pharmacokinetics of Meropenem Demonstrate the Need for Increasing Dose and Infusion Duration in Obese and Non-obese Patients

BACKGROUND AND OBJECTIVES

A quantitative evaluation of the PK of meropenem, a broad-spectrum β-lactam antibiotic, in plasma and interstitial space fluid (ISF) of subcutaneous adipose tissue of obese patients is lacking as of date. The objective of this study was the characterisation of meropenem population pharmacokinetics in plasma and ISF in obese and non-obese patients for identification of adequate dosing regimens via Monte-Carlo simulations.

METHODS

We obtained plasma and microdialysate concentrations after administration of meropenem 1000 mg to 15 obese and 15 non-obese surgery patients from a prospective clinical trial. After characterizing plasma- and microdialysis-derived ISF pharmacokinetics via population pharmacokinetic analysis, we simulated thrice-daily (TID) meropenem short-term (0.5 h), prolonged (3.0 h), and continuous infusions. Adequacy of therapy was assessed by the probability of pharmacokinetic/pharmacodynamic (PK/PD) target attainment (PTA) analysis based on time unbound concentrations exceeded minimum inhibitory concentrations (MIC) on treatment day 1 (%fT _{> MIC}) and the sum of PTA weighted by relative frequency of MIC values for infections by pathogens commonly treated with meropenem. To avoid interstitial tissue fluid concentrations below MIC for the entire dosing interval during continuous infusions, a more conservative PK/PD index was selected (%fT _{> 4 × MIC}).

RESULTS

Adjusted body weight (ABW) and calculated creatinine clearance (CLCR_{CG_ABW}) of all patients (body mass index [BMI] = 20.5-81.5 kg/m²) explained a considerable proportion of the between-patient pharmacokinetic variability (15.1-31.0% relative reduction). The ISF:plasma ratio of %fT _{> MIC} was relatively similar for MIC ≤ 2 mg/L but decreased for MIC = 8 mg/L over ABW = 60-120 kg (0.50-0.20). Steady-state concentrations were 2.68 times (95% confidence interval [CI] = 2.11-3.37) higher in plasma than in ISF, supporting PK/PD targets related to four times the MIC during continuous infusions to avoid suspected ISF concentrations constantly below the MIC. A 3000 mg/24 h continuous infusion was sufficient at MIC = 2 mg/L for patients with CLCR_{CG_ABW} ≤ 100 mL/min and ABW < 90 kg, whereas 2000 mg TID prolonged infusions were adequate for those with CLCR_{CG_ABW} ≤ 100 mL/min and ABW > 90 kg. For MIC = 2 mg/L and %fT_{> MIC} = 95, PTA was adequate in patients over the entire investigated range of body mass and renal function using a 6000 mg continuous infusion. A prolonged infusion of meropenem 2000 mg TID was sufficient for MIC ≤ 8 mg/L and all investigated ABW and CLCR_{CG_ABW} when employing the PK/PD target %fT _{> MIC} = 40. Short-term infusions of 1000 mg TID were sufficient for CLCR_{CG_ABW} ≤ 130 mL/min and distributions of MIC values for Escherichia coli, Citrobacter freundii, and Klebsiella pneumoniae but not for Pseudomonas aeruginosa.

CONCLUSIONS

This analysis indicated a need for higher doses (≥ 2000 mg) and prolonged infusions (≥ 3 h) for obese and non-obese patients at MIC ≥ 2 mg/L. Higher PTA was achieved with prolonged infusions in obese patients and with continuous infusions in non-obese patients.

TRIAL REGISTRATION

EudraCT: 2012-004383-22.

Development of a Model-Informed Dosing Tool to Optimise Initial Antibiotic Dosing-A Translational Example for Intensive Care Units

The prevalence and mortality rates of severe infections are high in intensive care units (ICUs). At the same time, the high pharmacokinetic variability observed in ICU patients increases the risk of inadequate antibiotic drug exposure. Therefore, dosing tailored to specific patient characteristics has a high potential to improve outcomes in this vulnerable patient population. This study aimed to develop a tabular dosing decision tool for initial therapy of meropenem integrating hospital-specific, thus far unexploited pathogen susceptibility information. An appropriate meropenem pharmacokinetic model was selected from the literature and evaluated using clinical data. Probability of target attainment (PTA) analysis was conducted for clinically interesting dosing regimens. To inform dosing prior to pathogen identification, the local pathogen-independent mean fraction of response (LPIFR) was calculated based on the observed minimum inhibitory concentrations distribution in the hospital. A simple, tabular, model-informed dosing decision tool was developed for initial meropenem therapy. Dosing recommendations achieving PTA > 90% or LPIFR > 90% for patients with different creatinine clearances were integrated. Based on the experiences during the development process, a generalised workflow for the development of tabular dosing decision tools was derived. The proposed workflow can support the development of model-informed dosing tools for initial therapy of various drugs and hospital-specific conditions.

Combination of pharmacokinetic and pathogen susceptibility information to optimize meropenem treatment of gram-negative infections in critically ill patients

Background: Meropenem is one of the most frequently used antibiotics to treat life-threatening infections in critically ill patients. This study aimed to develop a meropenem dosing algorithm for the treatment of gram-negative infections based on intensive care unit (ICU)-specific resistance data. Methods: Antimicrobial susceptibility testing of gram-negative bacteria obtained from critically ill patients was carried out from 2016 to 2020 at a tertiary care hospital. Based on the observed minimal inhibitory concentration (MIC) distribution, stochastic simulations (n=1000) of an evaluated pharmacokinetic meropenem model and a defined pharmacokinetic/pharmacodynamic target (100%T_>4xMIC while minimum concentrations <44.5 mg/L), dosing recommendations for patients with varying renal function were derived: Pathogen-specific MIC distributions were used to calculate the cumulative fraction of response (CFR) and the overall MIC distribution was used to calculate the local pathogen-independent mean fraction of response (LPIFR) for the investigated dosing regimens. A CFR/LPIFR >90% was considered adequate. Results: The observed MIC distribution significantly differed from the EUCAST database. Based on the 6520 MIC values included, a three-level dosing algorithm was developed. If the pathogen causing the infection is unknown (level 1), known (level 2), known to be neither Pseudomonas aeruginosa nor Acinetobacter baumannii or classified as susceptible (level 3), a continuous infusion of 1.5 g daily reached sufficient target attainment independent of renal function. In all other cases dosing needs to be adjusted based on renal function. Conclusion: ICU-specific susceptibility data should be assessed regularly and integrated into dosing decisions. The presented workflow may serve as a blueprint for other antimicrobial settings. (250 words).

Optimizing antimicrobial use: challenges, advances and opportunities

An optimal antimicrobial dose provides enough drug to achieve a clinical response while minimizing toxicity and development of drug resistance. There can be considerable variability in pharmacokinetics, for example, owing to comorbidities or other medications, which affects antimicrobial pharmacodynamics and, thus, treatment success. Although current approaches to antimicrobial dose optimization address fixed variability, better methods to monitor and rapidly adjust antimicrobial dosing are required to understand and react to residual variability that occurs within and between individuals. We review current challenges to the wider implementation of antimicrobial dose optimization and highlight novel solutions, including biosensor-based, real-time therapeutic drug monitoring and computer-controlled, closed-loop control systems. Precision antimicrobial dosing promises to improve patient outcome and is important for antimicrobial stewardship and the prevention of antimicrobial resistance.

Cerebrospinal Fluid Concentrations of Meropenem and Vancomycin in Ventriculitis Patients Obtained by TDM-Guided Continuous Infusion

Effective antibiotic therapy of cerebral infections such as meningitis or ventriculitis is hindered by low penetration into the cerebrospinal fluid (CSF). Because continuous infusion of meropenem and vancomycin and routine therapeutic drug monitoring (TDM) have been proposed to optimize antimicrobial exposure in ventriculitis patients, an individualized dosing strategy was implemented in our department. We present a retrospective analysis of meropenem and vancomycin concentrations in serum and CSF in the first nine ventriculitis patients treated with continuous infusion and TDM-guided dose optimization aiming at 20–30 mg/L. Median initial dosing was 8.8 g/24 h meropenem and 4.25 g/24 h vancomycin, respectively, resulting in median serum concentrations of 21.3 mg/L for meropenem and 24.5 mg/L for vancomycin and CSF concentrations of 3.4 mg/L for meropenem and 1.7 mg/L for vancomycin. Median CSF penetration was 15% for meropenem and 7% for vancomycin. With initial dosing, all but one patient achieved CSF concentrations above 1 mg/L. Dose adjustment according to TDM ensured sufficient CSF concentrations in all patients within 48 h of treatment. Given the limited penetration, continuous infusion of meropenem and vancomycin based on renal function and TDM-guided dose optimization appears a reasonable approach to attain sufficient CSF concentrations in ventriculitis patients.

Meropenem pharmacokinetics in critically ill patients with or without burn treated with or without continuous veno-venous hemofiltration

Introduction

Severe burn injury involves widespread skin and tissue damage leading to systemic inflammation, hypermetabolism and multi‐organ failure. The hypermetabolic phase of burn injury has been associated with increased systemic antibiotic clearance; however, critical illness in the absence of burn may also induce similar physiologic changes. Continuous renal replacement therapy (CRRT) is often implemented in critically ill patients and may also affect antibiotic clearance. Although the pharmacokinetics (PK) of meropenem has been described in both the burn and non‐burn critically ill populations, direct comparative data is lacking.

Methods

For this study, we evaluated PK parameters of meropenem from 23 critically ill patients, burn or non‐burn, treated with or without continuous veno‐venous haemofiltration (CVVH) to determine the contribution of burn and CVVH to the variability of therapeutic meropenem levels.

Results

A two‐compartment model best described the data and revealed creatinine clearance (CrCl) and total burn surface area (TBSA) as significant covariates on clearance (CL) and peripheral volume of distribution (Vp), respectively. Of interest, non‐burn patients on CVVH displayed an overall lower inherent CL as compared to burn patients on CVVH (6.43 vs. 12.85 L/h). Probability of target attainment (PTA) simulations revealed augmented renal clearance (ARC) may necessitate dose adjustments, but TBSA and CVVH would not.

Conclusions

We recommend a standard dose of 1000 mg every 8 hours; however, if ARC is suspected, or the severity of illness requires a more stringent therapeutic target, we recommend a loading dose of 1000–2000 mg infused over 30 minutes to 1 hour followed by continuous infusion (3000–6000 mg over 24 hours), or intermittent infusion of 2000 mg every 8 hours.

Evaluating prediction methods for glomerular filtration to optimise drug doses in obese and nonobese patients

AIMS

The most suitable method for predicting the glomerular filtration rate (GFR) in obesity is currently debated. Therefore, multiple GFR/creatinine clearance prediction methods were applied to (morbidly) obese and nonobese patients ranging from moderate renal impairment to glomerular hyperfiltration and their predictions were rated based on observed fosfomycin pharmacokinetics, as this model drug is exclusively eliminated via glomerular filtration.

METHODS

The GFR/creatinine clearance predictions via the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), Modification of Diet in Renal Disease (MDRD; indexed and de-indexed by body surface area) and creatinine clearance via the Cockcroft-Gault formula (CLCR_CG ) using different body size descriptors were compared to the fosfomycin clearance (CL_FOF ) from 30 surgical patients (body mass index = 20.1-52.0 kg m^-2 ), receiving 8000 mg as intravenous infusion.

RESULTS

The concordance between CL_FOF and creatinine clearance predictions was highest for CLCR_CG employing either ideal body weight or adjusted body weight (if body mass >1.3 ideal body weight; CLCR_{CG_ABW-Schwartz} , concordance-correlation coefficient [95% confidence interval] = 0.474 [0.156; 0.703], CCC) and GFR predictions via the de-indexed MDRD equation (concordance-correlation coefficient = 0.452 [0.137; 0.685]). The proportion of predicted GFR values within ±30% of the observed CL_FOF (P₃₀  = 72.3-76.7%) was only marginally lower than the reported P₃₀ in the original CKD-EPI and MDRD publications (P₃₀  = 84.1-90.0%).

CONCLUSION

This analysis represents a successful proof-of-concept for evaluating GFR/creatinine clearance prediction methods: Across all body mass index classes CLCR_{CG_ABW-Schwartz} or the de-indexed MDRD were most suitable for predicting creatinine clearance/GFR also in (morbidly) obese, CKD stage <3B individuals in therapeutic use. Their application is proposed in optimising doses for vital therapies in obese patients requiring monitoring of renal function (e.g. methotrexate dosing).

Beta-Lactams Dosing in Critically Ill Patients with Gram-Negative Bacterial Infections: A PK/PD Approach

Beta-lactam antibiotics are often the backbone of treatment for Gram-negative infections in the critically ill. Beta-lactams exhibit time-dependent killing, and their efficacy depends on the percentage of dosing interval that the concentration remains above the minimum inhibitory concentration. The Gram-negative resistance rates of pathogens are increasing in the intensive care unit (ICU), and critically ill patients often possess physiology that makes dosing more challenging. The volume of distribution is usually increased, and drug clearance is variable. Augmented renal clearance and hypermetabolic states increase the clearance of beta-lactams, while acute kidney injury reduces the clearance. To overcome the factors affecting ICU patients and decreasing susceptibilities, dosing strategies involving higher doses, and extended or continuous infusions may be required. In this review, we specifically examined pharmacokinetic models in ICU patients, to determine the desired beta-lactam regimens for clinical breakpoints of Enterobacterales and Pseudomonas aeruginosa, as determined by the European Committee on Antimicrobial Susceptibility Testing. The beta-lactams evaluated included penicillins, cephalosporins, carbapenems, and monobactams. We found that when treating less-susceptible pathogens, especially P. aeruginosa, continuous infusions are frequently needed to achieve the desired pharmacokinetic/pharmacodynamic targets. More studies are needed to determine optimal dosing strategies in the novel beta-lactams.

Impact of cumulative fluid balance on the pharmacokinetics of extended infusion meropenem in critically ill patients with sepsis

Background

Meropenem dosing for septic critically patients is difficult due to pathophysiological changes associated with sepsis as well as supportive symptomatic therapies. A prospective single-center study assessed whether fluid retention alters meropenem pharmacokinetics and the achievement of the pharmacokinetic/pharmacodynamic (PK/PD) targets for efficacy.

Methods

Twenty-five septic ICU patients (19 m, 6f) aged 32–86 years with the mean APACHE II score of 20.2 (range 11–33), suffering mainly from perioperative intra-abdominal or respiratory infections and septic shock (n = 18), were investigated over three days after the start of extended 3-h i.v. infusions of meropenem q8h. Urinary creatinine clearance (CL_cr) and cumulative fluid balance (CFB) were measured daily. Plasma meropenem was measured, and Bayesian estimates of PK parameters were calculated.

Results

Eleven patients (9 with peritonitis) were classified as fluid overload (FO) based on a positive day 1 CFB of more than 10% body weight. Compared to NoFO patients (n = 14, 11 with pneumonia), the FO patients had a lower meropenem clearance (CL_me 8.5 ± 3.2 vs 11.5 ± 3.5 L/h), higher volume of distribution (V₁ 14.9 ± 3.5 vs 13.5 ± 4.1 L) and longer half-life (t_1/2 1.4 ± 0.63 vs 0.92 ± 0.54 h) (p < 0.05). Over three days, the CFB of the FO patients decreased (11.7 ± 3.3 vs 6.7 ± 4.3 L, p < 0.05) and the PK parameters reached the values comparable with NoFO patients (CL_me 12.4 ± 3.8 vs 11.5 ± 2.0 L/h, V₁ 13.7 ± 2.0 vs 14.0 ± 5.1 L, t_1/2 0.81 ± 0.23 vs 0.87 ± 0.40 h). The CL_cr and Cockroft–Gault CL_cr were stable in time and comparable. The correlation with CL_me was weak to moderate (CL_cr, day 3 CGCL_cr) or absent (day 1 and 2 CGCL_cr). Dosing with 2 g meropenem q8h ensured adequate concentrations to treat infections with sensitive pathogens (MIC 2 mg/L). The proportion of pre-dose concentrations exceeding the MIC 8 mg/L and the fraction time with a target-exceeding concentration were higher in the FO group (day 1–3 f C_min > MIC: 67 vs 27%, p < 0.001; day 1%f T > MIC: 79 ± 17 vs 58 ± 17, p < 0.05).

Conclusions

These findings emphasize the importance of TDM and a cautious approach to augmented maintenance dosing of meropenem to patients with FO infected with less susceptible pathogens, if guided by population covariate relationships between CL_me and creatinine clearance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03680-9.

Development and validation of a dosing nomogram for amoxicillin in infective endocarditis

BACKGROUND

Amoxicillin is the first-line treatment for streptococcal or enterococcal infective endocarditis (IE) with a dose regimen adapted to weight.

OBJECTIVES

Covariates influencing pharmacokinetics (PK) of amoxicillin were identified in order to develop a dosing nomogram based on identified covariates for individual adaptation.

PATIENTS AND METHODS

Patients treated with amoxicillin administered by continuous infusion for IE were included retrospectively. The population PK analysis was performed using the Pmetrics package for R (NPAG algorithm). Influence of weight, ideal weight, height, BMI, body surface area, glomerular filtration rate adapted to the body surface area and calculated by the CKD-EPI method (mL/min), additional ceftriaxone treatment and serum protein level on amoxicillin PK was tested. A nomogram was then developed to determine the daily dose needed to achieve a steady-state free plasma concentration above 4× MIC, 100% of the time, without exceeding a total plasma concentration of 80 mg/L.

RESULTS

A total of 160 patients were included. Population PK analysis was performed on 540 amoxicillin plasma concentrations. A two-compartment model best described amoxicillin PK and the glomerular filtration rate covariate significantly improved the model when included in the calculation of the elimination constant Ke.

CONCLUSIONS

This work allowed the development of a dosing nomogram that can help to increase achievement of the PK/pharmacodynamic targets in IE treated with amoxicillin.

Population Pharmacokinetic Modeling and Simulations of Imipenem in Burn Patients With and Without Continuous Venovenous Hemofiltration in the Military Health System

Continuous venovenous hemofiltration (CVVH) is a life‐sustaining procedure in patients with severe burns and acute kidney injury. Physiologic changes from burn injury and use of CVVH may alter imipenem pharmacokinetics (PK). We aimed to compare imipenem clearance (CL) in burn patients with and without CVVH, determine the effect of burn on imipenem volume of distribution (CVVH, n = 12; no CVVH, n = 11), in combination with previously published models. Model qualification was performed with standard diagnostics and comparing predicted PK parameters/time‐concentration profiles with those in the existing literature. Monte Carlo simulations were conducted to evaluate the probability of target attainment. A 2‐compartment model best described the data. Utilizing albumin as a covariate on volume parameters and leveraging the clearance model from prior literature, our model predicted imipenem central volume and CL within a 10% margin of error across healthy, renally impaired, and burn populations. We provide direct comparison of imipenem CL in burn patients with and without CVVH. Notably, there was no significant difference. Large imipenem V_d in patients with severe burns is likely explained by increased capillary permeability, for which serum albumin may be a reasonable surrogate. Dosing 500 mg every 6 hours is adequate for burn patients on renally dosed CVVH; however, suspicion of augmented renal clearance or patients placed on CVVH without renal impairment may necessitate dosing of 1000 mg every 6 hours.

The Role of Non-Enzymatic Degradation of Meropenem-Insights from the Bottle to the Body

Several studies have addressed the poor stability of meropenem in aqueous solutions, though not considering the main degradation product, the open-ring metabolite (ORM) form. In the present work, we elucidate the metabolic fate of meropenem and ORM from continuous infusion to the human bloodstream. We performed in vitro infusate stability tests at ambient temperature with 2% meropenem reconstituted in 0.9% normal saline, and body temperature warmed buffered human serum with 2, 10, and 50 mg/L meropenem, covering the therapeutic range. We also examined meropenem and ORM levels over several days in six critically ill patients receiving continuous infusions. Meropenem exhibited a constant degradation rate of 0.006/h and 0.025/h in normal saline at 22 °C and serum at 37 °C, respectively. Given that 2% meropenem remains stable for 17.5 h in normal saline (≥90% of the initial concentration), we recommend replacement of the infusate every 12 h. Our patients showed inter-individually highly variable, but intra-individually constant molar ORM/(meropenem + ORM) ratios of 0.21–0.52. Applying a population pharmacokinetic approach using the degradation rate in serum, spontaneous degradation accounted for only 6% of the total clearance.

Personalized ß-lactam dosing in patients with coronavirus disease 2019 (COVID-19) and pneumonia: A retrospective analysis on pharmacokinetics and pharmacokinetic target attainment

ABSTRACT

Pathophysiological changes are important risk factors for critically ill patients with pneumonia manifesting sub-therapeutic antibiotic exposures during empirical treatment. The effect of coronavirus disease 2019 (COVID-19) on antibiotic dosing requirements is uncertain. We aimed to determine the effect of COVID-19 on ß-lactam pharmacokinetics (PK) and PK target attainment in critically ill patients with a personalized dosing strategy.Retrospective, single-center analysis of COVID-19 ± critically ill patients with pneumonia (community-acquired pneumonia or hospital-acquired pneumonia) who received continuous infusion of a ß-lactam antibiotic with dosing personalized through dosing software and therapeutic drug monitoring. A therapeutic exposure was defined as serum concentration between (css) 4 to 8 times the EUCAST non-species related breakpoint).Data from 58 patients with pneumonia was analyzed. Nineteen patients were tested COVID-19-positive before the start of the antibiotic therapy for community-acquired pneumonia or hospital-acquired pneumonia. Therapeutic exposure was achieved in 71% of COVID-19 patients (68% considering all patients). All patients demonstrated css above the non-species-related breakpoint. Twenty percent exceeded css above the target range (24% of all patients). The median ß-lactam clearance was 49% compared to ß-lactam clearance in a standard patient without a significant difference regarding antibiotic, time of sampling or present COVID-19 infection. Median daily doses were 50% lower compared to standard bolus dosing.COVID-19 did not significantly affect ß-lactam pharmacokinetics in critically ill patients. Personalized ß-lactam dosing strategies were safe in critically ill patients and lead to high PK target attainment with less resources.

Personalized Piperacillin Dosing for the Critically Ill: A Retrospective Analysis of Clinical Experience with Dosing Software and Therapeutic Drug Monitoring to Optimize Antimicrobial Dosing

Optimization of antibiotic dosing is a treatment intervention that is likely to improve outcomes in severe infections. The aim of this retrospective study was to describe the therapeutic exposure of steady state piperacillin concentrations (c_PIP) and clinical outcome in critically ill patients with sepsis or septic shock who received continuous infusion of piperacillin with dosing personalized through software-guided empiric dosing and therapeutic drug monitoring (TDM). Therapeutic drug exposure was defined as c_PIP of 32–64 mg/L (2–4× the ‘MIC breakpoint’ of Pseudomonas aeruginosa). Of the 1544 patients screened, we included 179 patients (335 serum concentrations), of whom 89% achieved the minimum therapeutic exposure of >32 mg/L and 12% achieved potentially harmful c_PIP > 96 mg/L within the first 48 h. Therapeutic exposure was achieved in 40% of the patients. Subsequent TDM-guided dose adjustments significantly enhanced therapeutic exposure to 65%, and significantly reduced c_PIP > 96 mg/L to 5%. Mortality in patients with c_PIP > 96 mg/L (13/21; 62%) (OR 5.257, 95% CI 1.867–14.802, p = 0.001) or 64–96 mg/L (30/76; 45%) (OR 2.696, 95% CI 1.301–5.586, p = 0.007) was significantly higher compared to patients with therapeutic exposure (17/72; 24%). Given the observed variability in critically ill patients, combining the application of dosing software and consecutive TDM increases therapeutic drug exposure of piperacillin in patients with sepsis and septic shock.

Population pharmacokinetics and probability of target attainment in patients with sepsis under renal replacement therapy receiving continuous infusion of meropenem: Sustained low-efficiency dialysis and continuous veno-venous haemodialysis

AIMS

To describe the population pharmacokinetics (PK) and probability of target attainment (PTA) of continuous infusion (CI) of meropenem in septic patients receiving renal replacement therapy (RRT).

METHODS

Fifteen patients without RRT, 13 patients receiving sustained low-efficiency dialysis and 12 patients receiving continuous veno-venous haemodialysis were included. Population PK analysis with Monte Carlo simulations for different dosing regimens was performed. For minimum inhibitory concentration 2 mg/L was chosen. The target was set as 50% time ≥4× minimum inhibitory concentration.

RESULTS

The PK of meropenem was best described by a 1-compartment model with linear elimination. Serum creatinine, residual diuresis and time on RRT, with no difference between sustained low-efficiency dialysis and continuous veno-venous haemodialysis, were found to be significant covariates affecting clearance, explaining >20% of the clearance between subject variability. PTA analysis showed that in patients with RRT, 2 g/24 h, meropenem CI achieved a PTA of 95%. In patients without RRT, the target was achieved with 3 g/24 h CI or prolonged infusion of 1 g meropenem over 8 hours but not with bolus application of 1 g meropenem for 8 hours. Only 2 patients (both without RRT) had meropenem concentrations below the target level. However, approximately half of the patients with RRT receiving CI 3 g/24 h meropenem had toxic concentrations.

CONCLUSION

We found relevant PK variability for meropenem CI in septic patients with or without RRT, leading to a substantial risk for overdosing in patients with RRT. This finding highlights the strong demand for personalized dosing in critically ill patients.

Carbapenem use in critically ill patients

PURPOSE OF REVIEW

To review available data on carbapenem use in ICU. Carbapenem is a broad spectrum well tolerated antibiotic family that keep an excellent activity to extended spectrum β-lactamases and AmpC hyperproducer and in susceptible Pseudomonas aeruginosa and Acinetobacter baumannii. It becomes a drug of choice for empirical therapy of suspected sepsis in known or presumably known ESBLE carriers.

RECENT FINDINGS

Carbapenems remained the drug of choice for severe ESBLE infections. In severe critically ill patients, high off-label dose is necessary especially in patients with sepsis and glomerular hyperfiltration. Nevertheless, large spectrum of carbapenems leads to initial overuse. The increase in the overall consumption in the past years with lack of systematic re-evaluation observed is responsible of and carbapenem-selection pressure that contribute to the increase of carbapenem-resistant enterobacteriaceae, A. Baumannii and P. Aeruginosa in ICUs.

SUMMARY

Carbapenems remained a cornerstone of antibiotic therapy of severe infections. Emerging carbapenem resistance is related to the increase of carbapenem consumption. High doses are recommended for early therapy followed by systematic reevaluation on a daily basis with shift to narrow spectrum antimicrobials if possible and early stopping rules.

Key Challenges in Providing Effective Antibiotic Therapy for Critically Ill Patients with Bacterial Sepsis and Septic Shock

Early initiation of effective antibiotic therapy is vitally important for saving the lives of critically ill patients with sepsis or septic shock. The susceptibility of the infecting pathogen and the ability of the selected dosage regimen to safely achieve the required antibiotic exposure need to be carefully considered to achieve a high probability of a successful outcome. Critically ill patients commonly experience substantial pathophysiological changes that impact the functions of various organs, including the kidneys. Many antibiotics are predominantly renally eliminated and thus renal function is a major determinant of the regimen needed to achieve the required antibiotic exposure. However, currently, there is a paucity of guidelines to inform antibiotic dosing in critically ill patients, including those with sepsis or septic shock. This paper briefly reviews methods that are commonly used in critically ill patients to provide a measure of renal function, and approaches that describe the relationship between the exposure to an antibiotic and its antibacterial effects. Two common conditions that very substantially complicate the use of antibiotics in critically ill patients with sepsis, unstable renal function, and augmented renal clearance, are considered in detail and their potential therapeutic implications are explored. Suggestions are provided on how treatment of bacterial infections in critically ill patients with sepsis might be improved. Of high potential are model-informed approaches that aim to individualize initial treatment regimens based on patient and bacterial characteristics, with refinement of regimens during treatment in response to monitoring antibiotic concentrations, responsive measures of renal function, and other important clinical data.

Meropenem use and therapeutic drug monitoring in clinical practice: a literature review

WHAT IS KNOWN AND OBJECTIVE

Meropenem, a carbapenem antibiotic, is widely prescribed for the treatment of life-threatening infections. The main parameter associated with its therapeutic success is the percentage of time that the levels remain above the minimum inhibitory concentration. Inadequate levels of meropenem can lead to therapeutic failure and increase the possibility of microbial resistance. The employment of strategies involving dose regimens and drug pharmacodynamics has become increasingly important to optimize therapies. In the present study, we conducted a review with the purpose of assembling information about the clinical use of meropenem and therapeutic drug monitoring.

METHODS

A literature review emphasizing the application of therapeutic drug monitoring (TDM) of meropenem in clinical practice has been done. To identify articles related to the topic, we performed a standardized search from January 21, 2020 to December 21, 2020, using specific descriptors in PubMed, Lilacs and Embase.

RESULTS AND DISCUSSION

In total, 35 studies were included in the review. The daily dose of meropenem commonly ranged from 3 to 6 g/day. Critically ill patients and those with impaired renal function appear to be the most suitable patients for the application of meropenem TDM, in order to guide therapy. We observed that most of the studies recommend TDM and that, in nine locations, the TDM of meropenem and of other beta-lactams is a routine practice. TDM data can help to maximize the clinical outcomes of the treatment with meropenem. It can also improve the patient care by providing suitable levels of meropenem, guiding the most appropriate dose regimens, which is the main parameter associated with therapeutic success.

WHAT IS NEW AND CONCLUSION

The findings from this review suggest that the therapeutic monitoring of meropenem can be beneficial, since it adjusts the treatment and aids clinical outcomes. It does so by indicating the appropriate dosage and preventing failure, toxicity and possible antimicrobial resistance. The multidisciplinary effort, basic knowledge and communication among the medical team are also essential.

A meropenem pharmacokinetics model in patients with haematological malignancies

Background

Optimal dosing of antibiotics is critical in immunocompromised patients suspected to have an infection. Data on pharmacokinetics (PK) of meropenem in patients with haematological malignancies are scarce.

Objectives

To optimize dosing regimens, we aimed to develop a PK population model for meropenem in this population.

Methods

Patients aged ≥18 years, hospitalized in the haematology department of our 1500 bed university hospital for a malignant haematological disease and who had received at least one dose of meropenem were eligible. Meropenem was quantified by HPLC. PK were described using a non-linear mixed-effect model and external validation performed on a distinct database. Monte Carlo simulations estimated the PTA, depending on renal function, duration of infusion and MIC. Target for free trough concentration was set at &gt;4× MIC.

Results

Overall, 88 patients (181 samples) were included, 66 patients (75%) were in aplasia and median Modification of Diet in Renal Disease (MDRD) CLCR was 117 mL/min/1.73 m2 (range: 35–359). Initial meropenem dosing regimen ranged from 1 g q8h to 2 g q8h over 30 to 60 min. A one-compartment model with first-order elimination adequately described the data. Only MDRD CLCR was found to be significantly associated with CL. Only continuous infusion achieved a PTA of 100% whatever the MIC and MDRD CLCR. Short duration of infusion (&lt;60 min) failed to reach an acceptable PTA, except for bacteria with MIC &lt; 0.25 mg/L in patients with MDRD CLCR below 90 mL/min/1.73 m2.

Conclusions

In patients with malignant haematological diseases, meropenem should be administered at high dose (6 g/day) and on continuous infusion to reach acceptable trough concentrations.

What Are the Current Approaches to Optimising Antimicrobial Dosing in the Intensive Care Unit?

Antimicrobial dosing in the intensive care unit (ICU) can be problematic due to various challenges including unique physiological changes observed in critically ill patients and the presence of pathogens with reduced susceptibility. These challenges result in reduced likelihood of standard antimicrobial dosing regimens achieving target exposures associated with optimal patient outcomes. Therefore, the aim of this review is to explore the various methods for optimisation of antimicrobial dosing in ICU patients. Dosing nomograms developed from pharmacokinetic/statistical models and therapeutic drug monitoring are commonly used. However, recent advances in mathematical and statistical modelling have resulted in the development of novel dosing software that utilise Bayesian forecasting and/or artificial intelligence. These programs utilise therapeutic drug monitoring results to further personalise antimicrobial therapy based on each patient’s clinical characteristics. Studies quantifying the clinical and cost benefits associated with dosing software are required before widespread use as a point-of-care system can be justified.

Population Pharmacokinetics of Imipenem in Critically Ill Patients: A Parametric and Nonparametric Model Converge on CKD-EPI Estimated Glomerular Filtration Rate as an Impactful Covariate

BACKGROUND

Population pharmacokinetic (popPK) models for antibiotics are used to improve dosing strategies and individualize dosing by therapeutic drug monitoring. Little is known about the differences in results of parametric versus nonparametric popPK models and their potential consequences in clinical practice. We developed both parametric and nonparametric models of imipenem using data from critically ill patients and compared their results.

METHODS

Twenty-six critically ill patients treated with intravenous imipenem/cilastatin were included in this study. Median estimated glomerular filtration rate (eGFR) measured by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation was 116 mL/min/1.73 m2 (interquartile range 104-124) at inclusion. The usual dosing regimen was 500 mg/500 mg four times daily. On average, five imipenem levels per patient (138 levels in total) were drawn as peak, intermediate, and trough levels. Imipenem concentration-time profiles were analyzed using parametric (NONMEM 7.2) and nonparametric (Pmetrics 1.5.2) popPK software.

RESULTS

For both methods, data were best described by a model with two distribution compartments and the CKD-EPI eGFR equation unadjusted for body surface area as a covariate on the elimination rate constant (Ke). The parametric population parameter estimates were Ke 0.637 h-1 (between-subject variability [BSV]: 19.0% coefficient of variation [CV]) and central distribution volume (Vc) 29.6 L (without BSV). The nonparametric values were Ke 0.681 h-1 (34.0% CV) and Vc 31.1 L (42.6% CV).

CONCLUSIONS

Both models described imipenem popPK well; the parameter estimates were comparable and the included covariate was identical. However, estimated BSV was higher in the nonparametric model. This may have consequences for estimated exposure during dosing simulations and should be further investigated in simulation studies.

External evaluation of population pharmacokinetic models for continuous administration of meropenem in critically ill adult patients

PURPOSE

Beta-lactams (BL), the most commonly prescribed class of antibiotics, are recommended as the first-line therapy for multiple indications in infectious disease guidelines. Meropenem (MERO) is frequently used in intensive care units (ICU) to treat bacterial infections with or without sepsis. The pharmacokinetics of MERO display a large variability in patients admitted to ICUs due to altered pathophysiology. The aim of this study was to perform an external evaluation of published population pharmacokinetic models of MERO in order to test their predictive performance in a cohort of ICU adult patients.

METHODS

A literature search in PubMed/Medline database was made following the PRISMA statement. External evaluation was performed using NONMEM software, and the bias and inaccuracy values were calculated.

RESULTS

An external validation dataset from the Timone Hospital in Marseille, France, included 84 concentration samples from 27 patients. Four models of MERO were identified according to the inclusion criteria of the study. None of the models presented acceptable values of bias and inaccuracy.

CONCLUSION

While performing external evaluations on some populations may confirm a model's suitability to diverse groups of patients, there is still some variability that cannot be explained nor solved by the procedure. This brings to light the difficulty to develop only one model for ICU patients and the need to develop one specific model to each population of critically ill patients.

Acute-on-chronic liver failure alters meropenem pharmacokinetics in critically ill patients with continuous hemodialysis: an observational study

BACKGROUND

Infection and sepsis are a main cause of acute-on-chronic liver failure (ACLF). Adequate dosing of antimicrobial therapy is of central importance to improve outcome. Liver failure may alter antibiotic drug concentrations via changes of drug distribution and elimination. We studied the pharmacokinetics of meropenem in critically ill patients with ACLF during continuous veno-venous hemodialysis (CVVHD) and compared it to critically ill patients without concomitant liver failure (NLF).

METHODS

In this prospective cohort study, patients received meropenem 1 g tid short-term infusion (SI). Meropenem serum samples were analyzed by high-performance liquid chromatography. A population pharmacokinetic analysis was performed followed by Monte Carlo simulations of (A) meropenem 1 g tid SI, (B) 2 g loading plus 1 g prolonged infusion tid (C) 2 g tid SI, and (D) 2 g loading and continuous infusion of 3 g/day on days 1 and 7. Probability of target attainment (PTA) was assessed for 4× the epidemiological cut-off values for Enterobacterales (4 × 0.25 mg/L) and Pseudomonas spp. (4 × 2 mg/L).

RESULTS

Nineteen patients were included in this study. Of these, 8 patients suffered from ACLF. A two-compartment model with linear clearance from the central compartment described meropenem pharmacokinetics. The peripheral volume of distribution (V₂) was significantly higher in ACLF compared to NLF (38.6L versus 19.7L, p = .05). PTA for Enterobacterales was achieved in 100% for all dosing regimens. PTA for Pseudomonas spp. in ACLF on day 1/7 was: A: 18%/80%, B: 94%/88%, C: 85%/98% D: 100%/100% and NLF: A: 48%/65%, B: 91%/83%, C: 91%/93%, D: 100%/100%.

CONCLUSION

ALCF patients receiving CVVHD had a higher V₂ and may require a higher loading dose of meropenem. For Pseudomonas, high doses or continuous infusion are required to reach PTA in ACLF patients.

Development and Validation of a Medication Selection Model Under Clinical Application of Renin-Angiotensin Inhibitor Combined with Calcium Channel Blocker for Hypertension Patients

Background

This study evaluated the impact of clinical features and concomitant conditions on the clinical selection of different renin-angiotensin system (RAS) inhibitors in patients with hypertension, and built a renin-angiotensin inhibitors selection model (RAISM) to provide a reference for clinical decision making.

Material/Methods

We included 213 hypertensive patients in the study cohort; patients were divided into two groups: the angiotensin-converting enzyme inhibitor (ACEI) combined with calcium channel blocker (CCB) group (ACEI+CCB group) and the angiotensin receptor antagonist (ARB) combined with CCB group (ARB+CCB group). Basic demographic characteristics and concomitant conditions of the patients were compared. Single-factor and multi-factor analysis was performed by adopting logistic regression model. The RAISM was established by utilizing the nomograph technology. C-index and calibration curve were used to evaluate the model’s efficacy.

Results

In the study, 34.27% of the patients used ACEI+CCB and 65.73% of patients used ARB+CCB. The difference in age, body mass index (BMI), elderly patient, diabetes, renal dysfunction, and hyperlipidemia between the 2 groups determined medication selection. To be specific, compared to the group using ARB+CCB, the odds ratios and 95% confidence interval (CI) of the aforementioned factors for the ACEI+CCB group were 0.476 (0.319–0.711), 1.274 (1.001–1.622), 0.365 (0.180–0.743), 0.471 (0.203–1.092), 0.542 (0.268–1.094), and 0.270 (0.100–0.728), respectively; The C-index of RAISM acquired from the model construction parameters was 0.699, and the correction curve demonstrated that the model has good discriminative ability.

Conclusions

The outcome of our study suggests that independent discriminating factors that influence the clinical selection of different RAS inhibitors were elderly patient, renal insufficiency, and hyperlipidemia; and the RAISM constructed in this study has good predictability and clinical benefit.

Therapeutic Drug Monitoring of Meropenem and Piperacillin in Critical Illness-Experience and Recommendations from One Year in Routine Clinical Practice

Various studies have reported insufficient beta-lactam concentrations in critically ill patients. The extent to which therapeutic drug monitoring (TDM) in clinical practice can reduce insufficient antibiotic concentrations is an ongoing matter of investigation. We retrospectively evaluated routine meropenem and piperacillin measurements in critically ill patients who received antibiotics as short infusions in the first year after initiating a beta-lactam TDM program. Total trough concentrations above 8.0 mg/L for meropenem and above 22.5 mg/L for piperacillin were defined as the breakpoints for target attainment. We included 1832 meropenem samples and 636 piperacillin samples. We found that 39.3% of meropenem and 33.6% of piperacillin samples did not reach the target concentrations. We observed a clear correlation between renal function and antibiotic concentration (meropenem, r = 0.53; piperacillin, r = 0.63). Patients with renal replacement therapy or creatinine clearance (CrCl) of <70 mL/min had high rates of target attainment with the standard dosing regimens. There was a low number of patients with a CrCl >100 mL/min that achieved the target concentrations with the maximum recommended dosage. Patients with impaired renal function only required TDM if toxic side effects were noted. In contrast, patients with normal renal function required different dosage regimens and TDM-guided therapy to reach the breakpoints of target attainment.

Comparative review of imipenem/cilastatin versus meropenem

INTRODUCTION

Carbapenems are broad-spectrum antibacterial molecules. Imipenem-cilastatin and meropenem are the two main molecules used in French healthcare services.

OBJECTIVE

We aimed to evaluate the relative strengths and weaknesses of these two molecules by considering their pharmacokinetic, pharmacodynamic, microbiological, and clinical properties. We demonstrated that imipenem-cilastatin and meropenem are not alike.

METHOD

Review of the literature by querying the MEDLINE network.

RESULTS

Imipenem-cilastatin is the first marketed molecule of the carbapenem class. It is more effective against Gram-positive cocci. Its stability does not allow for long infusions and its main adverse effect on the central nervous system limits its use. Meropenem is more effective against Gram-negative bacilli. Its stability and its milder adverse effects distinguish it from imipenem-cilastatin.

CONCLUSION

Meropenem is preferred for daily use in healthcare services when carbapenems are to be used.

PK/PD targets of amikacin and gentamicin in ICU patients

OBJECTIVES

We aimed to evaluate the probability to achieve PK-PD targets in patients with sepsis hospitalized in the intensive care unit (ICU) after a single dose of 30mg/kg of amikacin or 8mg/kg of gentamicin.

PATIENTS AND METHODS

This single-center prospective study included 138 ICU patients with severe sepsis or septic shock with an indication for intravenous amikacin (N=89) or gentamicin (N=49). Maximum concentration (C_max) was measured 30 minutes after infusion completion. PK/PD objectives were respectively C_max≥60mg/L and ≥30mg/L for amikacin and gentamicin for empirical therapy, and a C_max/MIC ratio≥8, as per French guidelines.

RESULTS

The median Simplified Acute Physiology Score II was 43 and ICU case fatality rate was 34.8%. A causative bacterial agent was identified in 94 patients (68.1%). Three pathogens had acquired aminoglycoside resistance and 15 were naturally resistant. The targeted C_max for the first dose was achieved in 53 patients (59.6%) receiving amikacin, and one (2.2%) patient receiving gentamicin. C_max/MIC ratio≥8 was obtained in all patients infected with susceptible pathogens (N=72). Factors associated with C_max≥60mg/L of amikacin in multivariate analysis were dose per kg of adapted body weight (OR=1.39, P<0.001) and renal clearance estimated with CKD-EPI formula (OR=0.98, P=0.003).

CONCLUSIONS

Despite high doses, amikacin and gentamicin first C_max remain dramatically low in ICU patients. However, an adequate C_max/MIC ratio was reached in all patients.