Assessment of pharmacokinetic changes of meropenem during therapy in septic critically ill patients

Does Two-Step Infusion Improve the Pharmacokinetics/Pharmacodynamics Target Attainment of Meropenem in Critically Ill Patients?

The optimal method for administering meropenem remains controversial. This study was conducted to explore the optimal two-step infusion strategy (TIT), and to investigate whether TIT is superior to intermittent infusion therapy (IIT) and prolonged infusion therapy (PIT). A physiologically based pharmacokinetics model for critically ill patients was established and evaluated. The validated model was utilized to evaluate the pharmacokinetics/pharmacodynamics (PK/PD) target attainment of meropenem. The PK/PD target attainment of different TITs varied greatly, and the total infusion duration and the first-step dose greatly affected these values. The optimal TIT was 0.25 g (30 min) + 0.75 g (150 min) at MICs of ≤2 mg/L, and 0.25 g (45 min) + 0.75 g (255 min) at MICs of 4-8 mg/L. The PK/PD target attainment of optimal TIT, PIT, and IIT were 100 % at MICs of ≤1 mg/L. When MIC increased to 2-8 mg/L, the PK/PD target attainment of optimal TIT was similar to that of PIT and higher than IIT. In conclusion, TIT did not significantly improve the PK/PD target attainment of meropenem compared with PIT. IIT is adequate at MICs of ≤1 mg/L, and PIT may be the optimal meropenem infusion method in critically ill patients with MICs of 2-8 mg/L.

Changes of PK/PD of Meropenem in patients with abdominal septic shock and exploration of clinical rational administration plan: a prospective exploratory study

This study aimed to explore the changes of pharmacokinetic parameters after meropenem in patients with abdominal septic shock after gastrointestinal perforation, and to simulate the probability of different dosing regimens achieving different pharmacodynamic goals. The study included 12 patients, and utilized high performance liquid chromatography-tandem mass spectrometry to monitor the plasma concentration of meropenem. The probability of target attainment (PTA) for different minimum inhibitory concentration (MIC) values and %fT > 4MIC was compared among simulated dosing regimens. The results showed that in 96 blood samples from 12 patients, the clearance (CL) of meropenem in the normal and abnormal creatinine clearance subgroups were 7.7 ± 1.8 and 4.4 ± 1.1 L/h, respectively, and the apparent volume of distribution (Vd) was 22.6 ± 5.1 and 17.2 ± 5.8 L, respectively. 2. Regardless of the subgroup, 0.5 g/q6h infusion over 6 h regimen achieved a PTA > 90% when MIC ≤ 0.5 mg/L. 1.0 g/q6h infusion regimen compared with other regimen, in most cases, the probability of making PTA > 90% is higher. For patients at low MIC, 0.5 g/q6h infusion over 6 h may be preferable. For patients at high MIC, a dose regimen of 1.0 g/q6 h infusion over 6 h may be preferable. Further research is needed to confirm this exploratory result.

Infections in lung transplanted patients: A review

Lung transplantation can improve the survival of patients with severe chronic pulmonary disorders. However, the short- and long-term risk of infections can increase morbidity and mortality rates. A non-systematic review was performed to provide the most updated information on pathogen, host, and environment-related factors associated with the occurrence of bacterial, fungal, and viral infections as well as the most appropriate therapeutic options. Bacterial infections account for about 50% of all infectious diseases in lung transplanted patients, while viruses represent the second cause of infection accounting for one third of all infections. Almost 10% of patients develop invasive fungal infections during the first year after lung transplant. Pre-transplantation comorbidities, disruption of physical barriers during the surgery, and exposure to nosocomial pathogens during the hospital stay are directly associated with the occurrence of life-threatening infections. Empiric antimicrobial treatment after the assessment of individual risk factors, local epidemiology of drug-resistant pathogens and possible drug-drug interactions can improve the clinical outcomes.

Meropenem population pharmacokinetics and model-based dosing optimisation in patients with serious bacterial infection

OBJECTIVES

The objective of this study was to develop a population pharmacokinetic model of meropenem in a heterogeneous population of patients with a serious bacterial infection in order to propose dosing optimisation leading to improved achievement of the pharmacokinetic/pharmacodynamic (PK/PD) target.

METHODS

A total of 174 meropenem serum levels obtained from 144 patients during therapeutic drug monitoring were analysed using a non-linear mixed-effects modelling approach and Monte Carlo simulation was then used to compare various dosing regimens in order to optimise PK/PD target attainment.

RESULTS

The meropenem volume of distribution of the patient population was 54.95 L, while clearance started at 3.27 L/hour and increased by 0.91 L/hour with each 1 mL/s/1.73 m2 of estimated glomerular filtration rate. Meropenem clearance was also 0.31 L/hour higher in postoperative patients with central nervous system infection. Meropenem administration by continuous infusion showed a significantly higher probability of attaining the PK/PD target than a standard 30 min infusion (95.3% vs 49.5%).

CONCLUSIONS

A daily meropenem dose of 3 g, 6 g and 10.5 g administered by continuous infusion was shown to be accurate for patients with moderate to severe renal impairment, normal renal function to mild renal impairment and augmented renal clearance, respectively.

Rationale and evidence for the use of new beta-lactam/beta-lactamase inhibitor combinations and cefiderocol in critically ill patients

BACKGROUND

Healthcare-associated infections involving Gram-negative bacteria (GNB) with difficult-to-treat resistance (DTR) phenotype are associated with impaired patient-centered outcomes and poses daily therapeutic challenges in most of intensive care units worldwide. Over the recent years, four innovative β-lactam/β-lactamase inhibitor (BL/BLI) combinations (ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam) and a new siderophore cephalosporin (cefiderocol) have been approved for the treatment of certain DTR-GNB infections. The literature addressing their microbiological spectrum, pharmacokinetics, clinical efficacy and safety was exhaustively audited by our group to support the recent guidelines of the French Intensive Care Society on their utilization in critically ill patients. This narrative review summarizes the available evidence and unanswered questions on these issues.

METHODS

A systematic search for English-language publications in PUBMED and the Cochrane Library database from inception to November 15, 2022.

RESULTS

These drugs have demonstrated relevant clinical success rates and a reduced renal risk in most of severe infections for whom polymyxin- and/or aminoglycoside-based regimen were historically used as last-resort strategies-namely, ceftazidime-avibactam for infections due to Klebsiella pneumoniae carbapenemase (KPC)- or OXA-48-like-producing Enterobacterales, meropenem-vaborbactam for KPC-producing Enterobacterales, ceftazidime-avibactam/aztreonam combination or cefiderocol for metallo-β-lactamase (MBL)-producing Enterobacterales, and ceftolozane-tazobactam, ceftazidime-avibactam and imipenem-relebactam for non-MBL-producing DTR Pseudomonas aeruginosa. However, limited clinical evidence exists in critically ill patients. Extended-infusion scheme (except for imipenem-relebactam) may be indicated for DTR-GNB with high minimal inhibitory concentrations and/or in case of augmented renal clearance. The potential benefit of combining these agents with other antimicrobials remains under-investigated, notably for the most severe presentations. Other important knowledge gaps include pharmacokinetic information in particular situations (e.g., pneumonia, other deep-seated infections, and renal replacement therapy), the hazard of treatment-emergent resistance and possible preventive measures, the safety of high-dose regimen, the potential usefulness of rapid molecular diagnostic tools to rationalize their empirical utilization, and optimal treatment durations. Comparative clinical, ecological, and medico-economic data are needed for infections in whom two or more of these agents exhibit in vitro activity against the causative pathogen.

CONCLUSIONS

New BL/BLI combinations and cefiderocol represent long-awaited options for improving the management of DTR-GNB infections. Several research axes must be explored to better define the positioning and appropriate administration scheme of these drugs in critically ill patients.

The expert clinical pharmacological advice program for tailoring on real-time antimicrobial therapies with emerging TDM candidates in special populations: how the ugly duckling turned into a swan

INTRODUCTION

The growing spread of infections caused by multidrug-resistant pathogens makes the need of tailoring antimicrobial therapies by means of a 'patient-centered' approach fundamental. In this scenario, therapeutic drug monitoring (TDM) of emerging antimicrobial candidates may be a valuable approach, but expert interpretation of TDM results should be granted for making them more clinically useful. The MD Clinical Pharmacologist may take over this task since this specialist may couple PK/PD expertise on drugs with a medical background and may provide expert interpretation of TDM results of antimicrobials for tailoring therapy on real-time in each single patient based on specific both drug/pathogen issues and patient issues.

AREAS COVERED

This article aims to highlight the main key-points and organizational aspects for implementing a successful TDM-based expert clinical pharmacological advice (ECPA) program for tailoring antimicrobial therapies on real-time in different hospitalized patient special populations.

EXPERT OPINION

TDM-based ECPA programs lead by the MD Clinical Pharmacologist may represent a way forward for maximizing clinical efficacy and for minimizing the risk of resistance developments and/or toxicity of antimicrobials. Stakeholders should be aware of the fact that this innovative approach may be cost-effective.

Individual Meropenem Clearance in Infants on ECMO and CVVHDF is Difficult to Predict: A Case Report and Review of the Literature

OBJECTIVES

Meropenem is a broad-spectrum carbapenem antibiotic with mostly renal excretion. Conflicting data are available regarding meropenem pharmacokinetics in critically ill neonates on concomitant continuous renal replacement therapy (CRRT) and/or extracorporeal membrane oxygenation (ECMO). Our objectives were to assess meropenem clearance in a neonate on CRRT and ECMO, compare it to previously published data and assess whether dose recommendations can be generalized in this population.

CASE DESCRIPTION

A 2.5 kg male infant with a large diaphragmatic hernia was delivered by cesarean section at week 35 and immediately mechanically ventilated due to shock and respiratory insufficiency. He underwent surgical correction of the hernia, but developed recurrent sepsis, multiorgan failure and pulmonary hypertension. He remained mechanically ventilated and required ECMO and continuous venovenous hemodiafiltration. He was started on meropenem 40 mg/kg/dose, every 8 hs for Enterobacter cloacae bacteremia and sepsis, but due to lack of clinical and microbiologic response despite in vitro susceptibility, he was started on a continuous meropenem infusion of 240 mg/kg/d, based on dose recommendations in a similar case. We measured steady state meropenem plasma concentrations on 2 occasions, during ECMO and continuous venovenous hemodiafiltration (CVVHDF) and then on CVVHDF only.

RESULTS

Meropenem serum concentrations were 90 and 64 mg/L on the first and second occasion (therapeutic target concentration, 10 mg/L) corresponding to a clearance of 1.9 and 2.6 mL/kg/min. This clearance estimate was substantially lower than that reported in toddlers on CRRT and ECMO in some studies.

CONCLUSION

In neonates and infants, meropenem clearance is difficult to predict because of dynamic ontogenetic changes in renal function. This problem is further aggravated in acutely ill infants with decreased renal function, renal replacement therapy and/or ECMO. Therefore, Target Concentration Intervention based on meropenem plasma concentrations is indispensable to ensure therapeutic exposure in this population.

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.

Prediction of Insufficient Beta-Lactam Concentrations in Extracorporeal Membranous Oxygenation Patients

BACKGROUND

The aim of this study was to identify predictors of insufficient beta-lactam concentrations in patients undergoing extracorporeal membrane oxygenation (ECMO).

METHODS

Retrospective analysis of all patients receiving ECMO support and treated with ceftazidime or cefepime (CEF), piperacillin/tazobactam (TZP), or meropenem (MEM). Trough drug concentrations (Cmin) were measured before the subsequent dose, according to the decision of the attending physician. Insufficient drug concentrations were identified if Cmin was below the clinical breakpoint of Pseudomonas aeruginosa.

RESULTS

A total of 222 Cmin (CEF, n = 41; TZP, n = 85; MEM, n = 96) from 110 patients were included; insufficient concentrations were observed in 26 (12%) antibiotic assessments; 21 (81%) of those occurred during MEM therapy. Insufficient Cmin were associated with a shorter time from initiation of antibiotics to measurement, a lower single dose of antibiotic, a higher creatinine clearance (CrCL), lower sequential organ failure assessment (SOFA) scores, and less use of continuous renal replacement therapy (CRRT) when compared to others.

CONCLUSIONS

Insufficient broad-spectrum beta-lactam concentrations were observed in 12% of drug measurement during ECMO therapy. Higher than recommended drug regimens could be considered in the very early phase of therapy and in those patients with augmented renal clearance and with less severe organ dysfunction.

Optimized Dosing Regimens of Meropenem in Septic Children Receiving Extracorporeal Life Support

Objectives: To develop a population pharmacokinetic model of meropenem in children with sepsis receiving extracorporeal life support (ECLS) and optimize the dosage regimen based on investigating the probability of target attainment (PTA). Methods: The children with sepsis were prospectively enrolled in a pediatric intensive care unit from January 2018 to December 2019. The concentration-time data were fitted using nonlinear mixed effect model approach by NONMEM program. The stochastic simulation considering various scenarios based on proposed population pharmacokinetics model were conducted, and the PTAs were calculated to optimize the dosage regimens. Results: A total of 25 children with sepsis were enrolled, of whom13 received ECMO, 9 received CRRT, and 4 received ECMO combined with CRRT. 12 children received a two-step 3-h infusion and 13 children received 1-h infusion. Bodyweight and creatinine clearance had significant impacts on the PK parameters. ECMO intervention was not related to the PK properties. If 100%T > MIC was chosen as target, children receiving 40 mg/kg q8h over a 3 h-infusion only reached the PTA up to 77.4%. If bacteria with MIC 2 mg/L were to be treated with meropenem and the PTA target was 50%T > MIC, a dose of 40 mg/kg q8h for 1 h infusion would be necessary. Conclusions: The PK properties of meropenem in septic children receiving extracorporeal life support were best described. We recommended the opitimized dosing regimens for septic children receiving ECLS depending on the PTA of PK target 50%T > MIC and 100%T > MIC, for children with sepsis during ECLS with different body weight, estimated creatinine clearance (eCRCL) and MIC of bacteria.

Optimizing Antimicrobial Drug Dosing in Critically Ill Patients

A fundamental step in the successful management of sepsis and septic shock is early empiric antimicrobial therapy. However, for this to be effective, several decisions must be addressed simultaneously: (1) antimicrobial choices should be adequate, covering the most probable pathogens; (2) they should be administered in the appropriate dose, (3) by the correct route, and (4) using the correct mode of administration to achieve successful concentration at the infection site. In critically ill patients, antimicrobial dosing is a common challenge and a frequent source of errors, since these patients present deranged pharmacokinetics, namely increased volume of distribution and altered drug clearance, which either increased or decreased. Moreover, the clinical condition of these patients changes markedly over time, either improving or deteriorating. The consequent impact on drug pharmacokinetics further complicates the selection of correct drug schedules and dosing during the course of therapy. In recent years, the knowledge of pharmacokinetics and pharmacodynamics, drug dosing, therapeutic drug monitoring, and antimicrobial resistance in the critically ill patients has greatly improved, fostering strategies to optimize therapeutic efficacy and to reduce toxicity and adverse events. Nonetheless, delivering adequate and appropriate antimicrobial therapy is still a challenge, since pathogen resistance continues to rise, and new therapeutic agents remain scarce. We aim to review the available literature to assess the challenges, impact, and tools to optimize individualization of antimicrobial dosing to maximize exposure and effectiveness in critically ill patients.

Prolonged Infusion of β-Lactams Decreases Mortality in Patients with Septic Shock: A Retrospective before-and-after Study

Septic shock substantially alters the pharmacokinetic properties of β-lactams with a subsequently high risk of insufficiently low serum concentrations and treatment failure. Considering their pharmacokinetic (PK)/pharmacodynamic (PD) index, prolonged infusions (PI) of β-lactams extend the time that the unbound fraction of the drug remains above the minimal inhibitory concentration MIC (ft _>MIC) and may improve patient survival. The present study is a monocentric, retrospective before-and-after analysis of septic shock patients treated with β-lactams. Patients of the years 2015–2017 received intermittent bolus application whereas patients of 2017–2020 received PI of β-lactams. The primary outcome was mortality at day 30 and 90 after diagnosis of septic shock. Mortality rates in the PI group were significantly lower on day 30 (PI: 41%, n = 119/290 vs. IB: 54.8%, n = 68/114; p = 0.0097) and day 90 (PI: 47.9%, n = 139/290 vs. IB: 62.9%, n = 78/124; p = 0.005). After propensity-score matching, 30- and 90-day mortality remained lower for the PI group (−10%, p = 0.14). PI was further associated with a reduction in the duration of invasive ventilation and a stronger decrease in SOFA scores within a 14 day-observation period. PI of β-lactams was associated with a significant reduction of mortality in patients with septic shock and may have beneficial effects on invasive ventilation and recovery from sepsis-related organ failure.

Comparison of two empirical prolonged infusion dosing regimens for meropenem in patients with septic shock: A two-center pilot study

BACKGROUND

Due to high pharmacokinetic variability, standard doses of meropenem are frequently inadequate in septic patients. Therapeutic drug monitoring of meropenem is not widely available; therefore, improved empiric dosing recommendations are needed.

OBJECTIVES

This study aimed to compare the attainment of pharmacologic targets for two common empirical dosing regimens for meropenem in patients with septic shock.

METHODS

Two empiric dosing schemes for meropenem were compared using extended infusions (120 minutes) in 32 patients with septic shock in the intensive care units at two different hospitals. One regimen was 3 × 2 g meropenem/24 h for two days, followed by 3 × 1 g meropenem/24 h; the other regimen was 4 × 1 g meropenem/24 h. Serum meropenem concentrations were measured for the first 72 h of therapy, and pharmacokinetic modelling was performed to define the percentage of time the free drug concentration was above various target MICs for each regimen (%fT_>MIC).

RESULTS

Both regimens led to a sufficiently high %fT_>MIC for pathogens with target MICs < 4 mg/L. When higher MICs were targeted, the %fT_>MIC of 4 × 1 g meropenem decreased faster than that of 3 × 2 g meropenem. At high MICs of 32 mg/L, both dosing regimens failed to provide appropriate drug concentrations. Renal function was a significant covariate of target attainment.

CONCLUSIONS

The results of this study can guide clinicians in their choice of an empirical dosing regimen for meropenem. If pathogens with low MICs (< 4 mg/L) are targeted, both dosing regimens are adequate, whereas more resistant strains require higher doses.

Clinical outcomes of empirical high-dose meropenem in critically ill patients with sepsis and septic shock: a randomized controlled trial

Background

Appropriate antimicrobial dosing is challenging because of changes in pharmacokinetics (PK) parameters and an increase in multidrug-resistant (MDR) organisms in critically ill patients. This study aimed to evaluate the effects of an empirical therapy of high-dose versus standard-dose meropenem in sepsis and septic shock patients.

Methods

We performed a prospective randomized open-label study to compare the changes of modified sequential organ failure assessment (mSOFA) score and other clinical outcomes of the high-dose meropenem (2-g infusion over 3 h every 8 h) versus the standard-dose meropenem (1-g infusion over 3 h every 8 h) in sepsis and septic shock patients. Patients' characteristics, clinical and microbiological outcomes, 14 and 28-day mortality, vasopressor- and ventilator-free days, intensive care unit (ICU) and hospital-free days, percent of the time of antibiotic concentrations above the minimum inhibitory concentration (%T>MIC), and safety were assessed.

Results

Seventy-eight patients were enrolled. Median delta mSOFA was comparable between two groups (- 1 in the high-dose group vs. - 1 in the standard-dose group; P value = 0.75). There was no difference between the two groups regarding clinical and microbiological cure, 14- and 28-day mortality, vasopressor- and ventilator-free days, and ICU- and hospital-free days. In patients admitted from the emergency department (ED) with a mSOFA score ≥ 7, the high-dose group demonstrated significantly better microbiological cure compared with the standard-dose group (75% (9/12 patients) vs. 20% (2/10 patients); P value = 0.03). Likewise, the high-dose group presented higher microbiological cure rate in patients admitted from ED who had either APACHE II score > 20 (83.3% (10/12) vs. 28.6% (2/7); P value = 0.045) or on mechanical ventilator (87.5% (7/8) vs. 23.1% (3/13); P value = 0.008) than the standard-dose group. Adverse events were comparable between the two groups.

Conclusions

Empirical therapy with the high-dose meropenem presented comparable clinical outcomes to the standard-dose meropenem in sepsis and septic shock patients. Besides, subgroup analysis manifested superior microbiological cure rate in sepsis or septic shock patients admitted from ED.

Trial registration

ClinicalTrials.gov, NCT03344627, registered on November 17, 2017.

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

Background

Optimal antibiotic exposure is a vital but challenging prerequisite for achieving clinical success in ICU patients.

Objectives

To develop and externally validate a population pharmacokinetic model for continuous-infusion meropenem in critically ill patients and to establish a nomogram based on a routinely available marker of renal function.

Methods

A population pharmacokinetic model was developed in NONMEM® 7.3 based on steady-state meropenem concentrations (CSS) collected during therapeutic drug monitoring. Different serum creatinine-based markers of renal function were compared for their influence on meropenem clearance (the Cockcroft-Gault creatinine clearance CLCRCG, the CLCR bedside estimate according to Jelliffe, the Chronic Kidney Disease Epidemiology Collaboration equation and the four-variable Modification of Diet in Renal Disease equation). After validation of the pharmacokinetic model with independent data, a dosing nomogram was developed, relating renal function to the daily doses required to achieve selected target concentrations (4/8/16 mg/L) in 90% of the patients. Probability of target attainment was determined for efficacy (CSS ≥8 mg/L) and potentially increased likelihood of adverse drug reactions (CSS >32 mg/L).

Results

In total, 433 plasma concentrations (3.20-48.0 mg/L) from 195 patients (median/P0.05 - P0.95 at baseline: weight 77.0/55.0-114 kg, CLCRCG 63.0/19.6-168 mL/min) were used for model building. We found that CLCRCG best described meropenem clearance (CL = 7.71 L/h, CLCRCG = 80 mL/min). The developed model was successfully validated with external data (n = 171, 73 patients). According to the nomogram, daily doses of 910/1480/2050/2800/3940 mg were required to reach a target CSS = 8 mg/L in 90% of patients with CLCRCG = 20/50/80/120/180 mL/min, respectively. A low probability of adverse drug reactions (<0.5%) was associated with these doses.

Conclusions

A dosing nomogram was developed for continuous-infusion meropenem based on renal function in a critically ill population.

Towards a Generic Tool for Prediction of Meropenem Systemic and Infection-Site Exposure: A Physiologically Based Pharmacokinetic Model for Adult Patients with Pneumonia

OBJECTIVE

The objective of this study was to develop a physiologically based pharmacokinetic model for meropenem using a retrograde approach, which could serve as a basis for prediction of the systemic and infection-site drug exposures in different populations and indications. We intended this model to be a useful tool to inform (local) pharmacokinetic-based optimal dosing of meropenem in different settings.

METHODS

We developed a reduced physiologically based pharmacokinetic model with NONMEM software using a top-down approach. We used historical (previously published) data for model development and qualification. We used steady-state systemic and infection-site concentrations from 60 adult patients diagnosed with severe lung infection for model development and internal evaluation. The data included rich plasma and sparse epithelial lining fluid samples. We based the internal validation of the model on successful numerical convergence, adequate precision in parameter estimation, acceptable goodness-of-fit plot with no indication of bias, and acceptable performance of visual predictive checks. We performed external validation by fitting the model to independent data from five previously published studies: four studies in patients with pneumonia, with different grades of renal impairment, and one study in morbidly obese patients.

RESULTS

We successfully fitted a reduced physiologically based pharmacokinetic model with six compartments (arterial and venous pools, infection site [lungs], liver, kidneys and rest of the body) to the data and adequately estimated model parameters. We successfully qualified the model (internally and externally) using established methods. Estimated values for tissue-to-plasma partition coefficients were 0.2629 and 0.1946 for lungs and non-fat tissues (kidneys and liver), respectively. Estimated total clearance was 8.174 L/h for a typical patient with a glomerular filtration rate of 65 mL/min. Consistent with the known mechanism of meropenem elimination and previously published models, renal clearance accounted for 70% of total clearance. The model had good predictive performances on data from five different sources including populations with different characteristics with regard to body size, renal function and morbidity.

CONCLUSIONS

We successfully developed a physiologically based pharmacokinetic model for meropenem in adult patients to be used as a basis for prediction of concentrations in different groups of patients, and eventually for effective dose individualisation in different subgroups of the population.

Scaling beta-lactam antimicrobial pharmacokinetics from early life to old age

AIMS

Beta-lactam dose optimization in critical care is a current priority. We aimed to review the pharmacokinetics (PK) of three commonly used beta-lactams (amoxicillin ± clavulanate, piperacillin-tazobactam and meropenem) to compare PK parameters reported in critically and noncritically ill neonates, children and adults, and to investigate whether allometric and maturation scaling principles could be applied to describe changes in PK parameters through life.

METHODS

A systematic review of PK studies of the three drugs was undertaken using MEDLINE and EMBASE. PK parameters and summary statistics were extracted and scaled using allometric principles to 70 kg individual for comparison. Pooled data were used to model clearance maturation and decline using a sigmoidal (Hill) function.

RESULTS

A total of 130 papers were identified. Age ranged from 29 weeks to 82 years and weight from 0.9-200 kg. PK parameters from critically ill populations were reported with wider confidence intervals than those in healthy volunteers, indicating greater PK variability in critical illness. The standard allometric size and sigmoidal maturation model adequately described increasing clearance in neonates, and a sigmoidal model was also used to describe decline in older age. Adult weight-adjusted clearance was achieved at approximately 2 years postmenstrual age. Changes in volume of distribution were well described by the standard allometric model, although amoxicillin data suggested a relatively higher volume of distribution in neonates.

CONCLUSIONS

Critical illness is associated with greater PK variability than in healthy volunteers. The maturation models presented will be useful for optimizing beta-lactam dosing, although a prospective, age-inclusive study is warranted for external validation.

Pharmacokinetics-pharmacodynamics issues relevant for the clinical use of beta-lactam antibiotics in critically ill patients

Antimicrobials are among the most important and commonly prescribed drugs in the management of critically ill patients and beta-lactams are the most common antibiotic class used. Critically ill patient's pathophysiological factors lead to altered pharmacokinetics and pharmacodynamics of beta-lactams.A comprehensive bibliographic search in PubMed database of all English language articles published from January 2000 to December 2017 was performed, allowing the selection of articles addressing the pharmacokinetics or pharmacodynamics of beta-lactam antibiotics in critically ill patients.In critically ill patients, several factors may increase volume of distribution and enhance renal clearance, inducing high intra- and inter-patient variability in beta-lactam concentration and promoting the risk of antibiotic underdosing. The duration of infusion of beta-lactams has been shown to influence the fT > minimal inhibitory concentration and an improved beta-lactam pharmacodynamics profile may be obtained by longer exposure with more frequent dosing, extended infusions, or continuous infusions.The use of extracorporeal support techniques in the critically ill may further contribute to this problem and we recommend not reducing standard antibiotic dosage since no drug accumulation was found in the available literature and to maintain continuous or prolonged infusion, especially for the treatment of infections caused by multidrug-resistant bacteria.Prediction of outcome based on concentrations in plasma results in overestimation of antimicrobial activity at the site of infection, namely in cerebrospinal fluid and the lung. Therefore, although no studies have assessed clinical outcome, we recommend using higher than standard dosing, preferably with continuous or prolonged infusions, especially when treating less susceptible bacterial strains at these sites, as the pharmacodynamics profile may improve with no apparent increase in toxicity.A therapeutic drug monitoring-guided approach could be particularly useful in critically ill patients in whom achieving target concentrations is more difficult, such as obese patients, immunocompromised patients, those infected by highly resistant bacterial strains, patients with augmented renal clearance, and those undergoing extracorporeal support techniques.

Maximally effective dosing regimens of meropenem in patients with septic shock

Objectives

To use a population pharmacokinetic approach to define maximally effective meropenem dosing recommendations for treatment of Acinetobacter baumannii and Pseudomonas aeruginosa infections in a large cohort of patients with septic shock.

Methods

Adult patients with septic shock and conserved renal function, treated with meropenem, were eligible for inclusion. Seven blood samples were collected during a single dosing interval and meropenem concentrations were measured by a validated HPLC-MS/MS method. Monte Carlo simulations were employed to define optimum dosing regimens for treatment of empirical or targeted therapy of A. baumannii and P. aeruginosa. EudraCT-no. 2014-002555-26 and NCT02240277.

Results

Fifty patients were included, 26 male and 24 female, with a median age of 64 years with an all-cause 90 day mortality of 34%. A two-compartment linear model including creatinine clearance (CLCR) as a covariate best described meropenem pharmacokinetics. For empirical treatment of A. baumannii, 2000 mg/6 h was required by intermittent (30 min) or prolonged (3 h) infusion, whereas 6000 mg/day was required with continuous infusion. For P. aeruginosa, 2000 mg/8 h or 1000 mg/6 h was required for both empirical and targeted treatment. In patients with a CLCR of ≤ 100 mL/min, successful concentration targets could be reached with intermittent dosing of 1000 mg/8 h.

Conclusions

In patients with septic shock and possible augmented renal clearance, doses should be increased and/or administration should be performed by prolonged or continuous infusion to increase the likelihood of achieving therapeutic drug concentrations. In patients with normal renal function, however, standard dosing seems to be sufficient.

A Nonparametric Pharmacokinetic Approach to Determine the Optimal Dosing Regimen for 30-Minute and 3-Hour Meropenem Infusions in Critically Ill Patients

BACKGROUND

Pharmacokinetics of meropenem differ widely in the critically ill population. It is imperative to maintain meropenem concentrations above the inhibitory concentrations for most of the interdose interval. A population pharmacokinetic/pharmacodynamic model was developed to determine the probability of target attainment for 3-hour and 30-minute infusion regimens in this population.

METHODS

This study was performed in an intensive care setting among adult patients who were initiated on meropenem at a dose of 1000 mg. Multiple blood specimens were collected at predetermined time points during the interdose period, and meropenem concentrations were measured using high performance liquid chromatography. Using Pmetrics, a pharmacokinetic/pharmacodynamic model was developed and validated. Monte Carlo simulation was performed, and probability of target attainment (100% T > minimum inhibitory concentration (MIC), with a probability >0.9) for doubling MICs was determined for different regimens of meropenem.

RESULTS

A 2-compartment multiplicative gamma error model best described the population parameters from 34 patients. The pharmacokinetic parameters used in the final model were Ke (elimination rate constant from the central compartment), Vc (volume of distribution of central compartment), KCP and KPC (intercompartmental rate constants), and IC2 (the fitted amount of meropenem in the peripheral compartment). Inclusion of creatinine clearance (CLcreat) and body weight as covariates improved the model prediction (Ke = Ke0 × (Equation is included in full-text article.), Vc = Vc0 × Weight). The Ke and Vc [geometric mean (range)] of the individuals were 0.54 (0.01-2.61)/h and 9.36 (4.35-21.62) L, respectively. The probability of attaining the target, T > MIC of 100%, was higher for 3-hour infusion regimens compared with 30-minute infusion regimens for all ranges of CLcreat.

CONCLUSIONS

This study emphasizes that extended regimens of meropenem are preferable for treating infections caused by bacteria with higher MICs. The nonparametric analysis using body weight and CLcreat as covariate adequately predicted the pharmacokinetics of meropenem in critically ill patients with a wide range of renal function.

Role of renal function in risk assessment of target non-attainment after standard dosing of meropenem in critically ill patients: a prospective observational study

Background

Severe bacterial infections remain a major challenge in intensive care units because of their high prevalence and mortality. Adequate antibiotic exposure has been associated with clinical success in critically ill patients. The objective of this study was to investigate the target attainment of standard meropenem dosing in a heterogeneous critically ill population, to quantify the impact of the full renal function spectrum on meropenem exposure and target attainment, and ultimately to translate the findings into a tool for practical application.

Methods

A prospective observational single-centre study was performed with critically ill patients with severe infections receiving standard dosing of meropenem. Serial blood samples were drawn over 4 study days to determine meropenem serum concentrations. Renal function was assessed by creatinine clearance according to the Cockcroft and Gault equation (CLCR_CG). Variability in meropenem serum concentrations was quantified at the middle and end of each monitored dosing interval. The attainment of two pharmacokinetic/pharmacodynamic targets (100%T_>MIC, 50%T_>4×MIC) was evaluated for minimum inhibitory concentration (MIC) values of 2 mg/L and 8 mg/L and standard meropenem dosing (1000 mg, 30-minute infusion, every 8 h). Furthermore, we assessed the impact of CLCR_CG on meropenem concentrations and target attainment and developed a tool for risk assessment of target non-attainment.

Results

Large inter- and intra-patient variability in meropenem concentrations was observed in the critically ill population (n = 48). Attainment of the target 100%T_>MIC was merely 48.4% and 20.6%, given MIC values of 2 mg/L and 8 mg/L, respectively, and similar for the target 50%T_>4×MIC. A hyperbolic relationship between CLCR_CG (25–255 ml/minute) and meropenem serum concentrations at the end of the dosing interval (C_8h) was derived. For infections with pathogens of MIC 2 mg/L, mild renal impairment up to augmented renal function was identified as a risk factor for target non-attainment (for MIC 8 mg/L, additionally, moderate renal impairment).

Conclusions

The investigated standard meropenem dosing regimen appeared to result in insufficient meropenem exposure in a considerable fraction of critically ill patients. An easy- and free-to-use tool (the MeroRisk Calculator) for assessing the risk of target non-attainment for a given renal function and MIC value was developed.

Trial registration

Clinicaltrials.gov, NCT01793012. Registered on 24 January 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1829-4) contains supplementary material, which is available to authorized users.

Population pharmacokinetics of meropenem in elderly patients: dosing simulations based on renal function

OBJECTIVES

The aim of this study was to evaluate different dosage regimens of meropenem in elderly patients in relation with renal function using a population pharmacokinetic (popPK) model.

METHODS

The data of 178 elderly patients treated with meropenem was collected from different sources. A popPK model was developed by using NONMEM® and the influence of different covariates on meropenem CL and V₁ was observed. Monte Carlo dosing simulations were performed at steady state to observe the % T > MIC for targets of 40, 60 and 80% of dosage intervals at different levels of creatinine clearance (CL_CR).

RESULTS

The data was described by a two-compartment model and the values of parameter estimates for CL, V₁, Q and V₂ were 5.27 L/h, 17.2 L, 9.92 L/h and 10.6 L, respectively. The CL_CR, body weight and centre had a significant influence on meropenem CL while no direct influence of age was observed. Extended infusions had pharmacokinetic and pharmacodynamic (PK/PD) breakpoint one dilution greater than corresponding short infusion regimens for each target of % T > MIC.

CONCLUSION

Meropenem CL was significantly lower in the elderly compared to CL reported in younger patients due to the reduced renal function. An extended infusion of 1000 mg q8h can be considered for empirical treatment of infections in elderly patients when CL_CR is ≤ 50 mL/min. A continuous infusion of 3000 mg daily dose is preferred if CL_CR > 50 mL/min. However, a higher daily dose of meropenem would be required for resistant strains (MIC >8 mg/L) of bacteria if CL_CR is >100 mL/min.

Pharmacokinetic/pharmacodynamic considerations for the optimization of antimicrobial delivery in the critically ill

PURPOSE OF REVIEW

Antimicrobials are very commonly used drugs in the intensive care setting. Extensive research has been conducted in recent years to describe their pharmacokinetics/pharmacodynamics in order to maximize the pharmacological benefit and patient outcome. Translating these new findings into clinical practice is encouraged.

RECENT FINDINGS

This article will discuss mechanistic data on factors causing changes in antimicrobial pharmacokinetics in critically ill patients, such as the phenomena of augmented renal clearance as well as the effects of hypoalbuminemia, renal replacement therapy, and extracorporeal membrane oxygenation. Failure to achieve clinical cure has been correlated with pharmacokinetics/pharmacodynamics target nonattainment, and a recent meta-analysis suggests an association between dosing strategies aimed at optimizing antimicrobial pharmacokinetics/pharmacodynamics with improvement in clinical cure and survival. Novel dosing strategies including therapeutic drug monitoring are also now being tested to address challenges in the optimization of antimicrobial pharmacokinetics/pharmacodynamics.

SUMMARY

Optimization of antimicrobial dosing in accordance with pharmacokinetics/pharmacodynamics targets can improve survival and clinical cure. Dosing regimens for critically ill patients should aim for pharmacokinetics/pharmacodynamics target attainment by utilizing altered dosing strategies including adaptive feedback using therapeutic drug monitoring.

Serum β-lactam concentrations in critically ill patients with cirrhosis: a matched case-control study

BACKGROUND & AIMS

The pharmacokinetics of β-lactam antibiotics have not been well defined in critically ill patients with cirrhosis.

METHODS

We reviewed data from critically ill patients with cirrhosis and matched controls in whom routine therapeutic drug monitoring of two broad-spectrum β-lactam antibiotics (piperacillin/tazobactam and meropenem) had been performed. Serum drug concentrations were measured twice by high-performance liquid chromatography. Antibiotic pharmacokinetics were calculated using a one-compartment model. We considered that therapy was adequate when serum drug concentrations were between 4 and 8 times the minimal inhibitory concentration of Pseudomonas aeruginosa during optimal periods of time for each drug (≥ 50% for piperacillin/tazobactam; ≥ 40% for meropenem).

RESULTS

We studied 38 patients with cirrhosis (16 for piperacillin/tazobactam and 22 for meropenem) and 38 matched controls. Drug dosing was similar in the two groups. The pharmacokinetics analysis showed a lower volume of distribution of meropenem (P = 0.05) and a lower antibiotic clearance of piperacillin/tazobactam (P = 0.009) in patients with cirrhosis than in the matched controls. Patients with cirrhosis were more likely than those without cirrhosis to have excessive serum β-lactam concentrations (P = 0.015), in particular for piperacillin/tazobactam.

CONCLUSIONS

Standard β-lactam antibiotics regimens resulted in excessive serum concentrations in two thirds of the patients with cirrhosis. This was particularly true for piperacillin/tazobactam, probably because of reduced drug clearance.

Pharmacodynamic Evaluation of the Potential Clinical Utility of Fosfomycin and Meropenem in Combination Therapy against KPC-2-Producing Klebsiella pneumoniae

KPC-producing Klebsiella pneumoniae causes serious infections associated with high death rates worldwide. Combination therapy consisting of fosfomycin and a carbapenem is better than monotherapy to combat multidrug-resistant microorganisms, but no dosages for the combination have been defined. The MICs of meropenem and fosfomycin were evaluated against 18 clinical isolates of KPC-2-producing K. pneumoniae The activities of combination antimicrobials were also determined by the checkerboard method. The MIC50 and MIC90 of each agent alone and in combination were challenged against short (1.5-h) or prolonged (3-h) infusion regimens of meropenem (1 g every 8 h [q8h], 1.5 g q6h, 2 g q8h) and fosfomycin (4 g q8h, 6 g q6h, 8 g q8h) by Monte Carlo simulation to evaluate the time above the MIC of the free drug concentration as a percentage of the dosing interval (fT>MIC). The monotherapy MIC50s and MIC90s were 32 and 256 mg/liter for meropenem and 64 and 512 mg/liter for fosfomycin, respectively. Antimicrobial combination increased bacterial susceptibility to 1/4 the MIC50s and to 1/8 to 1/16 the MIC90s of monotherapy. The antimicrobial combination demonstrated a synergistic effect for at least two-thirds of the isolates. In combination therapy, fosfomycin regimens of 6 g q6h and 8 g q8h as a 3-h infusion against the MIC50 and MIC90 had better chances of achieving ≥90% probability of target attainment (PTA) of 70% fT>MIC. Meropenem regimens of 1.5 g q6h and 2 g q8h in prolonged infusion can achieve close to 90% PTA of 40% fT>MIC for MIC50 but not MIC90 The significant reduction in the MIC values and the achievement of appropriate PTA demonstrated that regimens containing fosfomycin with meropenem can be effective against KPC-2-producing K. pneumoniae.

Therapeutic drug monitoring of anti-infective agents in critically ill patients

Initial adequate anti-infective therapy is associated with significantly improved clinical outcomes for patients with severe infections. However, in critically ill patients, several pathophysiological and/or iatrogenic factors may affect the pharmacokinetics of anti-infective agents leading to suboptimal drug exposure, in particular during the early phase of therapy. Therapeutic drug monitoring (TDM) may assist to overcome this problem. We discuss the available evidence on the use of TDM in critically ill patient populations for a number of anti-infective agents, including aminoglycosides, β-lactams, glycopeptides, antifungals and antivirals. Also, we present the available evidence on the practices of anti-infective TDM and describe the potential utility of TDM to improve treatment outcome in critically ill patients with severe infections. For aminoglycosides, glycopeptides and voriconazole, beneficial effects of TDM have been established on both drug effectiveness and potential side effects. However, for other drugs, therapeutic ranges need to be further defined to optimize treatment prescription in this setting.

Population pharmacokinetics and probability of target attainment of meropenem in critically ill patients

PURPOSE

Patients admitted to intensive care unit (ICU) with Klebsiella pneumoniae infections are characterized by high mortality. The aims of the present study were to investigate the population pharmacokinetics parameters and to assess the probability of target attainment of meropenem in critically ill patients to provide information for more effective regimens.

METHODS

Twenty-seven consecutive patients were included in the study. Meropenem was administered as 3-h intravenous (i.v.) infusions at doses of 1-2 g every 8 or 12 h. Meropenem plasma concentrations were measured by a high-performance liquid chromatography (HPLC) method, and a population pharmacokinetics analysis was performed using NONMEM software. Meropenem plasma disposition was simulated for extended (3 h; 5 h) or continuous i.v. infusions, and the following parameters were calculated: time during which free drug concentrations were above minimum inhibitory concentration (MIC) (fT > MIC), free minimum plasma concentrations above 4× MIC (fCmin > 4× MIC), probability of target attainment (PTA), and cumulative fraction of response (CFR).

RESULTS

Gender and severity of sepsis affected meropenem clearance, whose typical population values ranged from 6.22 up to 12.04 L/h (mean ± standard deviation (SD) value, 9.38 ± 4.47 L/h). Mean C min value was 7.90 ± 7.91 mg/L, suggesting a high interindividual variability. The simulation confirmed that 88 and 97.5 % of patients achieved effective C min > 4× MIC values after 3- and 5-h i.v. infusions of meropenem 2 g × 3/day, respectively. On the contrary, the same total daily doses reached the target C min > 4× MIC values in 100 % of patients when administered as continuous i.v. infusions.

CONCLUSIONS

Several factors may influence meropenem pharmacokinetics in ICU patients. Continuous i.v. infusions of meropenem seem to be more effective than standard regimens to achieve optimal therapeutic targets.

Personalised beta-lactam therapy: basic principles and practical approach

Bacterial infections are potentially life-threatening diseases requiring effective antibiotic treatment right from the outset to achieve a favourable prognosis. Therapeutic success depends on the susceptibility of the bacterial pathogen, determined by the minimum inhibitory concentration (MIC), and the concentration of the antibiotic at the focus of infection, which is influenced by drug metabolism and pharmacokinetic (PK) factors. Beta-lactams are time-dependent antibiotics. Bacterial killing correlates with the duration of the drug concentration above the MIC of the pathogen. Critical illness is associated with major PK changes. This may lead to unexpected drug concentrations and unpredictable dose requirements differing significantly from standard dosages. Emerging dosing strategies are therefore based on PK/pharmacodynamic (PD) principles. Therapeutic drug monitoring (TDM) is increasingly playing a key role in antibiotic treatment optimisation in general and in beta-lactam therapy, in particular, notably in severely ill patients. Furthermore, evidence of the superiority of continuous beta-lactam infusions over shorter administration regimens is growing. Target drug concentrations have to be defined, considering MIC values especially in pathogens with limited susceptibility. For reliable TDM results, correct pre-analytical sample handling is indispensable. Personalised, TDM-guided therapy currently offers the most promising approach to assuring that beta-lactam treatment is effective, especially in critically ill patients.

No Development of Imipenem Resistance in Pneumonia Caused by Escherichia coli

BACKGROUND

Antibiotic resistance continues to rise due to the increased number of antibiotic prescriptions and is now a major threat to public health. In particular, there is an increase in antibiotic resistance to Escherichia coli according to the latest reports.

TRIAL DESIGN

This article examines, retrospectively, antibiotic resistance in patients with community- and nosocomial-acquired pneumonia caused by E coli.

METHODS

The data of all patients with community- and nosocomial-acquired pneumonia caused by E coli were collected from the hospital charts at the HELIOS Clinic, Witten/Herdecke University, Wuppertal, Germany, within the study period 2004 to 2014. An antibiogram was performed for the study patients with pneumonia caused by E coli. Antimicrobial susceptibility testing was performed for the different antibiotics that have been consistently used in the treatment of patients with pneumonia caused by E coli. All demographic, clinical, and laboratory data of all of the patients with pneumonia caused by E coli were collected from the patients' records.

RESULTS

During the study period of January 1, 2004 to August 12, 2014, 135 patients were identified with community- and nosocomial-acquired pneumonia affected by E coli. These patients had a mean age of 72.5 ± 11.6 (92 [68.1%, 95% CI 60.2%-76.0%] males and 43 [31.9%, 95% CI 24.0%-39.8%] females). E coli had a high resistance rate to ampicillin (60.7%), piperacillin (56.3%), ampicillin-sulbactam (44.4%), and co-trimoxazole (25.9%). No patients with pneumonia caused by E coli showed resistance to imipenem (P < 0.0001).

CONCLUSION

E coli was resistant to many of the typically used antibiotics. No resistance was detected toward imipenem in patients with pneumonia caused by E coli.

Population pharmacokinetics and Monte Carlo dosing simulations of meropenem during the early phase of severe sepsis and septic shock in critically ill patients in intensive care units

Pathophysiological changes during the early phase of severe sepsis and septic shock in critically ill patients, resulting in altered pharmacokinetic (PK) patterns for antibiotics, are important factors influencing therapeutic success. The aims of this study were (i) to reveal the population PK parameters and (ii) to assess the probability of target attainment (PTA) for meropenem. The PK studies were carried out following administration of 1 g of meropenem every 8 h during the first 24 h of severe sepsis and septic shock in nine patients, and a Monte Carlo simulation was performed to determine the PTA of achieving 40% exposure time during which the free plasma drug concentration remains above the MIC (fT>MIC) and 80% fT>MIC. The volume of distribution (V) and total clearance (CL) of meropenem in these patients were 23.7 liters and 7.82 liters/h, respectively. For pathogens with MICs of 4 μg/ml, the PTAs of 40% fT>MIC following administration of meropenem as a 1-h infusion of 1 g every 8 h and a 4-h infusion of 0.5 g every 8 h were 92.52% and 90.29%, respectively. For pathogens with MICs of 2 μg/ml in immunocompromised hosts, the PTAs of 80% fT>MIC following administration of 1-h and 4-h infusions of 2 g of meropenem every 8 h were 84.32% and 94.72%, respectively. These findings indicated that the V of meropenem was greater and the CL of meropenem was lower than the values obtained in a previous study with healthy subjects. The maximum recommended dose, i.e., 2 g of meropenem every 8 h, may be required for treatment of life-threatening infections in this patient population.

The combined effects of extracorporeal membrane oxygenation and renal replacement therapy on meropenem pharmacokinetics: a matched cohort study

INTRODUCTION

The scope of extracorporeal membrane oxygenation (ECMO) is expanding; however, optimal drug prescription during ECMO remains a developing science. Currently, there are no clear guidelines for antibiotic dosing during ECMO. This open-label, descriptive, matched-cohort pharmacokinetics (PK) study aimed to compare the PK of meropenem in ECMO patients to critically ill patients with sepsis not receiving ECMO (controls).

METHODS

Eleven adult patients on ECMO (venovenous (VV) ECMO, n = 6; venoarterial (VA) ECMO, n = 5) receiving intravenous (IV) meropenem were included. Meropenem plasma concentrations were determined using validated chromatography. Population PK analysis was performed using non-linear mixed effects modelling. This data was compared with previously published meropenem PK data from 10 critically ill adult patients not on ECMO (preserved renal function (n = 5) or receiving renal replacement therapy (RRT) (n = 5). Using these data, we then performed Monte Carlo simulations (n = 1,000) to describe the effect of creatinine clearance on meropenem plasma concentrations.

RESULTS

In total, five (two VV, three VA) out of eleven ECMO patients received RRT. The other six patients (four VV, two VA) had no significant impairment in renal function. A two-compartment model adequately described the data. ECMO patients had numerically higher volume of distribution (0.45 ± 0.17 versus 0.41 ± 0.13 L/kg, P = 0.21) and lower clearance compared to controls (7.9 ± 5.9 versus 11.7 ± 6.5 L/h, P = 0.18). Variability in meropenem clearance was correlated with creatinine clearance or the presence of RRT. The observed median trough concentrations in the controls were 4.2 (0.0 to 5.7) mg/L. In ECMO patients, while trough meropenem concentrations >2 mg/L were achieved in all patients, a more aggressive target of >8 mg/L for less susceptible microorganisms was observed in only eight out of eleven patients, with five of them being on RRT.

CONCLUSIONS

ECMO patients exhibit high PK variability. Decreased meropenem CL on ECMO appears to compensate for ECMO and critical illness-related increases in volume of distribution. Routine target concentrations >2 mg/L are maintained with standard dosing (1 g IV 8-hourly). However, an increase in dose may be necessary when targeting higher concentrations or in patients with elevated creatinine clearance.