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

Population pharmacokinetics and dosing simulations of meropenem in septic critically ill patients with complicated intra-abdominal infection or pneumonia

OBJECTIVES

Meropenem pharmacokinetics (PK) may be altered in septic critically ill patients with complicated intra-abdominal infections (cIAI) and pneumonia. We aimed to evaluate the covariates affecting meropenem PK and the performance of different dosing regimens to optimize the PK/pharmacodynamic target.

METHODS

Population PK analysis was performed using non-linear mixed-effects modeling. The final model was validated and used to simulate meropenem exposure to assess the probability of attaining the 100 %ƒT>MIC target.

RESULTS

Forty-six and 14 patients were respectively enrolled for PK analysis and external validation. A one-compartment linear model adequately described the data of 226 concentrations. The typical clearance (CL) and volume of distribution (Vd) were 9.69 L/h and 27.4 L, respectively. Septic shock from cIAI (cIASS) and actual body weight were significant covariates for meropenem Vd in addition to the influential covariates of creatinine clearance (CLCR-CG) and augmented renal clearance for CL. External validation showed the robustness and accuracy of this model. Simulation results proposed continuous infusion (CI) dosing regimens of meropenem against pathogens with MICs ≥ 2 mg/L in patients with cIASS and CLCR-CG ≥ 60 mL/min.

CONCLUSIONS

For the patients with cIASS and CLCR-CG ≥ 60 mL/min, CI meropenem is proposed for treatment of less sensitive pathogens with MICs ≥ 2 mg/L.

Is the high dose extended infusion of meropenem useful in the treatment of highly resistant gram-negative bacteria in children?

OBJECTIVES

Multidrug resistant infections present a treatment challenge for clinicians. These infections have been associated with increased morbidity and mortality. Recently, there has been increasing discussion in the literature that high dose extended infusion of meropenem may be helpful. We aimed to evaluate the clinical efficacy of high dose extended infusion of meropenem in the treatment of highly resistant Gram-negative infections.

METHODS

This retrospective observational study was conducted between December 2014 and December 2020 at Hacettepe University Ihsan Dogramaci Children's Hospital. Clinical and microbiological data of children diagnosed with invasive multidrug and extremely drug resistant Gram-negative infections were studied. The findings of patients given high dose extended infusion of meropenem were compared with patients who received colistin or tigecycline.

RESULTS

Overall, 158 pediatric patients infected with multidrug and extremely drug resistant gram-negatives were enrolled; 76 treated with high-dose prolonged infusion of meropenem; 60 treated with colistin and 22 with tigecycline. The overall clinical response at the end of the treatment was 81.6 % in meropenem group, 83.3 % in colistin group and 77.3 % in tigecycline group (P = 0.821). Microbiological response at the end of the treatment was 81.1 % in meropenem group, 76.4 % in colistin group and 72.2 % in tigecycline group (P = 0.694).

CONCLUSION

Meropenem, with an adjusted dose (high-dose and extended), seems a crucial and robust fighting agent in the treatment of pediatric patients infected with highly-resistant Gram-negative bacteria. It may also be useful in preventing the use of the latest fighting tools such as colistin and tigecycline during the antibacterial stewardship process.

Optimization of meropenem continuous infusion based on Monte Carlo simulation integrating with degradation study

OBJECTIVE

Meropenem degradation poses a challenge to continuous infusion (CI) implementation. However, data about the impact of degradation on the probability of target attainment (PTA) of meropenem has been limited. This study evaluated the stability of meropenem brands and the consequence of in-bottle degradation on PTA in different environmental scenarios.

METHOD

Seven meropenem generic brands prepared at concentrations of 1 g/48mL and 2 g/48mL in saline were examined at 25, 30, and 37°C over 8 h. A linear mixed-effects model was used to estimate degradation rate constant and potential covariates. In-bottle stability data was subsequently integrated as input for a deterministic and stochastic simulation using a published population pharmacokinetic model of critical illness. The impact of the degradation on target attainment at 98%fT>MIC was assessed.

RESULTS

Time, temperature, and infusion concentration were factors affecting the stability of the meropenem solution for all products. The differences in the degradation of seven generics were subtle, so their simulated plasma concentrations were equal. Meropenem CI with 8 h renewal infusion achieved a higher PTA than the extended 3 h infusion, even at the highest degradation condition. The impact of meropenem degradation on PTA was minimal vis-à-vis the meropenem dose, patient's renal function, and microbial susceptibility. Meropenem degradation reduced PTA by an observable magnitude in patients with augmented renal clearance and difficult-to-treat pathogens. Dose escalation up to 1.5-2g every 8 h could restore this reduction to the target 90% PTA.

CONCLUSION

Meropenem CI with 8 h of renewal infusion, considering stability even in tropical areas, was feasible to maximize the efficacy to difficult-to-treat pathogens.

The relation between inflammatory biomarkers and drug pharmacokinetics in the critically ill patients: a scoping review

BACKGROUND

The level of inflammation alters drug pharmacokinetics (PK) in critically ill patients. This might compromise treatment efficacy. Understanding the specific effects of inflammation, measured by biomarkers, on drug absorption, distribution, metabolism, and excretion is might help in optimizing dosing strategies.

OBJECTIVES

This review investigates the relationship between inflammatory biomarkers and PK parameters absorption, distribution, metabolism and excretion (ADME) in critically ill patients, providing insight in the complexity of dosing drugs in critically ill patients.

METHOD

Following PRISMA guidelines, we conducted a comprehensive search of Medline, Embase, Web of Science, and Cochrane databases (January 1946-November 2023). Studies examining inflammatory biomarkers, PK parameters, or drug exposure in critically ill patients were included. Records were screened by title, abstract, and full text, with any discrepancies resolved through discussion or consultation with a third reviewer.

RESULTS

Of the 4479 records screened, 31 met our inclusion criteria: 2 on absorption, 7 on distribution, 17 on metabolism, and 6 on excretion. In general, results are only available for a limited number of drugs, and most studies are done only looking at one of the components of ADME. Higher levels of inflammatory biomarkers may increase or decrease drug absorption depending on whether the drug undergoes hepatic first-pass elimination. For drug distribution, inflammation is negatively correlated with drug protein binding capacity, positively correlated with cerebrospinal fluid penetration, and negatively correlated with peritoneal penetration. Metabolizing capacity of most drugs was inversely correlated with inflammatory biomarkers. Regarding excretion, inflammation can lead to reduced drug clearance, except in the neonatal population.

CONCLUSION

Inflammatory biomarkers can offer valuable information regarding altered PK in critically ill patients. Our findings emphasize the need to consider inflammation-driven PK variability when individualizing drug therapy in this setting, at the same time research is limited to certain drugs and needs further research, also including pharmacodynamics.

Impact of Continuous Infusion Meropenem PK/PD Target Attainment on C-Reactive Protein Dynamics in Critically Ill Patients With Documented Gram-Negative Hospital-Acquired or Ventilator-Associated Pneumonia

BACKGROUND AND OBJECTIVE

Population pharmacokinetic/pharmacodynamic (PK/PD) modelling of antibiotics including C-reactive protein (C-RP) dynamics could be helpful in predicting the efficacy of antimicrobials. We developed a PK/PD model for assessing the impact of continuous infusion (CI) meropenem PK/PD target attainment on C-RP dynamics in critically ill patients with documented Gram-negative hospital- (HAP) or ventilator-acquired pneumonia (VAP).

METHODS

Patients were grouped according to the type of antibiotic treatment received [meropenem monotherapy; meropenem plus empirical anti-MRSA (methicillin-resistant Staphylococcus aureus) therapy; meropenem in combination with another anti-Gram-negative active agent; meropenem plus a targeted anti-MRSA therapy]. A one-compartment population PK model of CI meropenem was developed by including all patients. A full C-RP production inhibition model was developed for fitting the PD data by including only patients receiving meropenem monotherapy or meropenem plus empirical anti-MRSA therapy. Monte Carlo simulations explored the relationship between the type of PK/PD target attainment of CI meropenem, defined as optimal (steady-state plasma concentration [Css] to minimum inhibitory concentration [MIC] ratio = 4-8), quasi-optimal (Css/MIC = 1-4) and sub-optimal (Css/MIC < 1) and the magnitude of C-RP production inhibition over time.

RESULTS

A total of 64 patients providing 211 meropenem concentrations were included in the PK analysis, whereas 47 patients providing 328 C-RP data were included in the PD model. Simulations showed that optimal PK/PD target attainment was associated with the highest and most rapid C-RP production inhibition (44% and 56% at days 2 and 4, respectively). Conversely, sub-optimal PK/PD target attainment was shown to be almost ineffective (< 5% at day 4 and < 10% at day 10).

CONCLUSION

Our PK/PD model predicted that attaining optimal PK/PD target with CI meropenem may grant prompt and intense C-RP decrease among critically ill patients receiving targeted monotherapy for Gram-negative HAP/VAP, thus anticipating efficacy.

Risk Factors Associated with Antibiotic Exposure Variability in Critically Ill Patients: A Systematic Review

(1) Background: Knowledge about the behavior of antibiotics in critically ill patients has been increasing in recent years. Some studies have concluded that a high percentage may be outside the therapeutic range. The most likely cause of this is the pharmacokinetic variability of critically ill patients, but it is not clear which factors have the greatest impact. The aim of this systematic review is to identify risk factors among critically ill patients that may exhibit significant pharmacokinetic alterations, compromising treatment efficacy and safety. (2) Methods: The search included the PubMed, Web of Science, and Embase databases. (3) Results: We identified 246 observational studies and ten clinical trials. The most studied risk factors in the literature were renal function, weight, age, sex, and renal replacement therapy. Risk factors with the greatest impact included renal function, weight, renal replacement therapy, age, protein or albumin levels, and APACHE or SAPS scores. (4) Conclusions: The review allows us to identify which critically ill patients are at a higher risk of not reaching therapeutic targets and helps us to recognize the extensive number of risk factors that have been studied, guiding their inclusion in future studies. It is essential to continue researching, especially in real clinical practice and with clinical outcomes.

Population pharmacokinetics of meropenem in critically ill patients

Objective

The pharmacokinetics of meropenem are significantly altered in critically ill patients. A population pharmacokinetic study was designed to estimate typical values of meropenem clearance in critically ill patients and evaluate potential factors of influence.

Methods

After meropenem reached a steady state in each patient, two blood samples were taken within the dose interval. The one-compartment pharmacokinetic model based on the data from 101 intensive care unit patients was built using NONMEM software.

Results

Typical values of meropenem clearance and volume of distribution were 3.80 L/h and 3.52 L, respectively. In the final model, meropenem clearance was influenced by serum concentrations of creatinine (CRE), leukocyte count (WBC), hypertension (HTA), and concomitant use of vancomycin (VAN) or colistimethate (COL): CL (L/h) = 5.29 × CRE ^ 0.000001 × WBCs ^ (-0.165) + 0.000001 × HTA + 0.825 × VAN + 1.28 × COL.

Conclusion

In order to achieve effective plasma concentrations of meropenem in critically ill patients, the meropenem dosing regimen should be adjusted according to individual values of drug clearance.

NOTICE OF DUPLICATE PUBLICATION: "Stability of meropenem in portable elastomeric infusion devices: which protocol should be implemented in clinical practice?"

The American Society for Microbiology (ASM) and Microbiology Spectrum are withdrawing the article mentioned below as it is an inadvertent duplicate publication: Esteban-Cartelle B, Serrano DR, Pérez Menéndez-Conde C, Vicente-Oliveros N, Álvarez-Díaz A, Abete JF, Martín-Dávila P. 2024. Stability of meropenem in portable elastomeric infusion devices: which protocol should be implemented in clinical practice? Microbiol Spectr 12:e02063-23. https://doi.org/10.1128/spectrum.02063-23. This article was accidentally published twice in the journal due to a technical error, and there are no ethical or integrity concerns regarding the original published article. The duplicate version of the article has been withdrawn to correct the scholarly record. The original published article and its content are not affected by this withdrawal and can be found here: https://journals.asm.org/doi/10.1128/spectrum.02064-23 The American Society for Microbiology apologizes to the authors and its readers for the technical error and the inconvenience this may have caused. The authors agreed with the publication of this notice.

Stability of meropenem in portable elastomeric infusion devices: which protocol should be implemented in clinical practice?

IMPORTANCE

Although outpatient parenteral antibiotic therapy can be a good approach to treating infections, a lack of data regarding antibiotic stability in portable elastomeric infusion devices restricts its safe and effective use. Actually, meropenem is used for prolonged periods above 24 h, and it is not physicochemically stable, which can compromise efficacy and toxicity. This work is of high importance to show the clinicians the real shelf life of meropenem when administered in portable elastomeric infusion devices. We propose several administration protocols for meropenem in portable elastomeric infusion devices in clinical practice, according to the stability drug results obtained in our study.

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.

Meropenem Pharmacokinetics and Target Attainment in Critically Ill Patients

Purpose

This study aimed to investigate the pharmacokinetics and target attainment of meropenem and compare the effect of meropenem dosing regimens in critically ill patients.

Patients and Methods

Thirty-seven critically ill patients who were administered meropenem in intensive care units were analyzed. Patients were classified according to their renal function. Pharmacokinetic parameters were assessed based on Bayesian estimation. The target attainment of 40%fT > MIC (fraction time that the free concentration exceeds the minimum inhibitory concentration) and 100%fT > MIC with the pathogen MIC of 2 mg/L and 8 mg/L were specially focused. Furthermore, the effects of standard dosing (1g meropenem, 30 min intravenous infusion every 8h) and non-standard dosing (dosage regimens except standard dosing) were compared.

Results

The results showed that the values of meropenem clearance (CL), central volume of distribution (V1), intercompartmental clearance (Q), and peripheral volume of distribution (V2) were 3.3 L/h, 9.2 L, 20.1 L/h and 12.8 L, respectively. The CL of the patients among renal function groups was significantly different (p < 0.001). The tow targets attainment for the pathogen MIC of 2 mg/L and 8 mg/L were 89%, 73%, 49% and 27%, respectively. The severe renal impairment group has higher fraction of target attainment than the other group. The standard dosing achieved the target of 40%fT > 2/8 mg/L (85.7% and 81%, respectively) and patients with severe renal impairment achieved the target fraction of 100% for 40%fT > MIC. Additionally, there was no significant difference between standard and non-standard dosing group in target attainment.

Conclusion

Our findings indicate that renal function is an important covariate for both meropenem pharmacokinetics parameters and target attainment. The target attainment between standard and non-standard dosing group was not comparable. Therefore, therapeutic drug monitoring is indispensable in the dosing adjustment for critically ill patients if it is available.

A Systematic Review on Antimicrobial Pharmacokinetic Differences between Asian and Non-Asian Adult Populations

While the relevance of inter-ethnic differences to the pharmacokinetic variabilities of antimicrobials has been reported in studies recruiting healthy subjects, differences in antimicrobial pharmacokinetics between Asian and non-Asian patients with severe pathologic conditions require further investigation. For the purpose of describing the potential differences in antimicrobial pharmacokinetics between Asian and non-Asian populations, a systematic review was performed using six journal databases and six theses/dissertation databases (PROSPERO record CRD42018090054). The pharmacokinetic data of healthy volunteers and non-critically ill and critically ill patients were reviewed. Thirty studies on meropenem, imipenem, doripenem, linezolid, and vancomycin were included in the final descriptive summaries. In studies recruiting hospitalised patients, inconsistent differences in the volume of distribution (V_d) and drug clearance (CL) of the studied antimicrobials between Asian and non-Asian patients were observed. Additionally, factors other than ethnicity, such as demographic (e.g., age) or clinical (e.g., sepsis) factors, were suggested to better characterise these pharmacokinetic differences. Inconsistent differences in pharmacokinetic parameters between Asian and non-Asian subjects/patients may suggest that ethnicity is not an important predictor to characterise interindividual pharmacokinetic differences between meropenem, imipenem, doripenem, linezolid, and vancomycin. Therefore, the dosing regimens of these antimicrobials should be adjusted according to patients' demographic or clinical characteristics that can better describe pharmacokinetic differences.

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.

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.

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.

Pharmacodynamics of Piperacillin-Tazobactam/Amikacin Combination versus Meropenem against Extended-Spectrum β-Lactamase-Producing Escherichia coli in a Hollow Fiber Infection Model

Carbapenems are recommended for the treatment of urosepsis caused by extended-spectrum β-lactamase (ESBL)-producing, multidrug-resistant Escherichia coli; however, due to selection of carbapenem resistance, there is an increasing interest in alternative treatment regimens including the use of β-lactam-aminoglycoside combinations. We compared the pharmacodynamic activity of piperacillin-tazobactam and amikacin as mono and combination therapy versus meropenem monotherapy against extended-spectrum β-lactamase (ESBL)-producing, piperacillin-tazobactam resistant E. coli using a dynamic hollow fiber infection model (HFIM) over 7 days. Broth-microdilution was performed to determine the MIC of E. coli isolates. Whole genome sequencing was conducted. Four E. coli isolates were tested in HFIM with an initial inoculum of ~107 CFU/mL. Dosing regimens tested were piperacillin-tazobactam 4.5 g, 6-hourly, plus amikacin 30 mg/kg, 24-hourly, as combination therapy, and piperacillin-tazobactam 4.5 g, 6-hourly, amikacin 30 mg/kg, 24-hourly, and meropenem 1 g, 8-hourly, each as monotherapy. We observed that piperacillin-tazobactam and amikacin monotherapy demonstrated initial rapid bacterial killing but then led to amplification of resistant subpopulations. The piperacillin-tazobactam/amikacin combination and meropenem experiments both attained a rapid bacterial killing (~4-5 log10) within 24 h and did not result in any emergence of resistant subpopulations. Genome sequencing demonstrated that all ESBL-producing E. coli clinical isolates carried multiple antibiotic resistance genes including blaCTX-M-15, blaOXA-1, blaEC, blaTEM-1, and aac(6')-Ib-cr. These results suggest that the combination of piperacillin-tazobactam/amikacin may have a potential role as a carbapenem-sparing regimen, which should be tested in future urosepsis clinical trials.

Double-, single- and none-carbapenem-containing regimens for the treatment of carbapenem-resistant Enterobacterales (CRE) bloodstream infections: a retrospective cohort

OBJECTIVES

To investigate the effect of double-, single- and none-carbapenem-containing antimicrobial regimens in the treatment of patients with carbapenem-resistant Enterobacterales (CRE) bloodstream infections (BSIs).

METHODS

We conducted a retrospective cohort study from 2013 to 2020 in two Brazilian hospitals. Patients ≥18 years old with CRE BSI were included and excluded if death or treatment duration for ≤48 h after BSI or non-Class A-producing carbapenemase isolates. We evaluated the impact of different carbapenem-containing regimens on 30 day mortality through a propensity score adjusted model and a Cox proportional hazards model.

RESULTS

Two-hundred and seventy-nine patients were included for analyses: 47 (16.9%), 149 (53.4%) and 83 (29.8%) were treated with double-, single- and none-carbapenem-containing regimens, respectively. One-hundred and seventeen (41.9%) patients died in 30 days. Treatment with a single-carbapenem regimen was associated with a lower risk of death in 30 days compared with therapies containing no carbapenem [adjusted HR (aHR) 0.66, 95% CI 0.44-0.99, P = 0.048], when adjusted for Charlson score and ICU admission at baseline, while double-carbapenem regimens were not associated with a lower risk of death (aHR 0.78, 95% CI 0.46-1.32, P = 0.35). Propensity score adjusted model results went in the same direction.

CONCLUSIONS

Double-carbapenem- was not superior to single-carbapenem-containing regimens in patients with CRE BSIs. Single-carbapenem-containing schemes were associated with a lower mortality risk.

Tissue Penetration of Antimicrobials in Intensive Care Unit Patients: A Systematic Review—Part I

The challenging severity of some infections, especially in critically ill patients, makes the diffusion of antimicrobial drugs within tissues one of the cornerstones of chemotherapy. The knowledge of how antibacterial agents penetrate tissues may come from different sources: preclinical studies in animal models, phase I–III clinical trials and post-registration studies. However, the particular physiopathology of critically ill patients may significantly alter drug pharmacokinetics. Indeed, changes in interstitial volumes (the third space) and/or in glomerular filtration ratio may influence the achievement of bactericidal concentrations in peripheral compartments, while inflammation can alter the systemic distribution of some drugs. On the contrary, other antibacterial agents may reach high and effective concentrations thanks to the increased tissue accumulation of macrophages and neutrophils. Therefore, the present review explores the tissue distribution of beta-lactams and other antimicrobials acting on the cell wall and cytoplasmic membrane of bacteria in critically ill patients. A systematic search of articles was performed according to PRISMA guidelines, and tissue/plasma penetration ratios were collected. Results showed a highly variable passage of drugs within tissues, while large interindividual variability may represent a hurdle which must be overcome to achieve therapeutic concentrations in some compartments. To solve that issue, off-label dosing regimens could represent an effective solution in particular conditions.

Plasma and Cerebrospinal Fluid Population Pharmacokinetics of Meropenem in Neurocritical Care Patients: a Prospective Two-Center Study

Morbidity and mortality related to ventriculitis in neurocritical care patients remain high. Antibiotic dose optimization may improve therapeutic outcomes. In this study, a population pharmacokinetic model of meropenem in infected critically ill patients was developed. We applied the final model to determine optimal meropenem dosing regimens required to achieve targeted cerebrospinal fluid exposures. Neurocritical care patients receiving meropenem and with a diagnosis of ventriculitis or extracranial infection were recruited from two centers to this study. Serial plasma and cerebrospinal fluid samples were collected and assayed. Population pharmacokinetic modeling and Monte Carlo dosing simulations were performed using Pmetrics. We sought to determine optimized dosing regimens that achieved meropenem cerebrospinal fluid concentrations above pathogen MICs for 40% of the dosing interval, or a higher target ratio of meropenem cerebrospinal fluid trough concentrations to pathogen MIC of ≥1. In total, 53 plasma and 34 cerebrospinal fluid samples were obtained from eight patients. Meropenem pharmacokinetics were appropriately described using a three-compartment model with linear plasma clearance scaled for creatinine clearance and cerebrospinal fluid penetration scaled for patient age. Considerable interindividual pharmacokinetic variability was apparent, particularly in the cerebrospinal fluid. Percent coefficients of variation for meropenem clearance from plasma and cerebrospinal fluid were 41.7% and 89.6%, respectively; for meropenem, the volume of distribution in plasma and cerebrospinal fluid values were 63.4% and 58.3%, respectively. High doses (up to 8 to 10 g/day) improved attainment of meropenem cerebrospinal fluid target exposures, particularly for less susceptible organisms (MICs, ≥0.25 mg/L). Standard meropenem doses of 2 g every 8 h may not achieve effective concentrations in cerebrospinal fluid in all critically ill patients. Higher doses, or alternative dosing methods (e.g., loading dose followed by continuous infusion) may be required to optimize cerebrospinal fluid exposures. Doses of up to 8 to 10 g/day either as intermittent boluses or continuous infusion would be suitable for patients with augmented renal clearance; lower doses may be considered for patients with impaired renal function as empirical suggestions. Ongoing dosing should be tailored to the individual patient circumstances. Notably, the study population was small and dosing recommendations may not be generalizable to all critically ill patients.

Evaluating Mono- and Combination Therapy of Meropenem and Amikacin against Pseudomonas aeruginosa Bacteremia in the Hollow-Fiber Infection Model

Debate continues as to the role of combination antibiotic therapy for the management of Pseudomonas aeruginosa infections. We studied the extent of bacterial killing by and the emergence of resistance to meropenem and amikacin as monotherapies and as a combination therapy against susceptible and resistant P. aeruginosa isolates from bacteremic patients using the dynamic in vitro hollow-fiber infection model. Three P. aeruginosa isolates (meropenem MICs of 0.125, 0.25, and 64 mg/L) were used, simulating bacteremia with an initial inoculum of ~1 × 105 CFU/mL and the expected pharmacokinetics of meropenem and amikacin in critically ill patients. For isolates susceptible to amikacin and meropenem (isolates 1 and 2), the extent of bacterial killing was increased with the combination regimen compared with the killing by monotherapy of either antibiotic. Both the combination and meropenem monotherapy were able to sustain bacterial killing throughout the 7-day treatment course, whereas regrowth of bacteria occurred with amikacin monotherapy after 12 h. For the meropenem-resistant P. aeruginosa isolate (isolate 3), only the combination regimen demonstrated bacterial killing. Given that tailored antibiotic regimens can maximize potential synergy against some isolates, future studies should explore the benefit of combination therapy against resistant P. aeruginosa. IMPORTANCE Current guidelines recommend that aminoglycosides should be used in combination with β-lactam antibiotics as initial empirical therapy for serious infections, and otherwise, patients should receive β-lactam antibiotic monotherapy. Given the challenges associated with studying the clinical effect of different antibiotic strategies on patient outcomes, useful data for subsequent informed clinical testing can be obtained from in vitro models like the hollow-fiber infection model (HFIM). Based on the findings of our HFIM, we propose that the initial use of combination therapy with meropenem and amikacin provides some bacterial killing against carbapenem-resistant P. aeruginosa isolates. For susceptible isolates, combination therapy may only be of benefit in specific patient populations, such as critically ill or immunocompromised patients. Therefore, clinicians may want to consider using the combination therapy for the initial management and ceasing the aminoglycosides once antibiotic susceptibility results have been obtained.

Pharmacodynamic evaluation of piperacillin/tazobactam versus meropenem against extended-spectrum β-lactamase-producing and non-producing Escherichia coli clinical isolates in a hollow-fibre infection model

BACKGROUND

Urosepsis caused by extended-spectrum β-lactamase (ESBL)-producing Escherichia coli is increasing worldwide. Carbapenems are commonly recommended for the treatment of ESBL infections; however, to minimize the emergence of carbapenem resistance, interest in alternative treatments has heightened.

OBJECTIVES

This study compared pharmacodynamics of piperacillin/tazobactam versus meropenem against ESBL-producing and non-producing E. coli clinical isolates.

METHODS

E. coli isolates, obtained from national reference laboratory in Bangladesh, were characterized by phenotypic tests, WGS, susceptibility tests and mutant frequency analysis. Three ESBL-producing and two non-producing E. coli were exposed to piperacillin/tazobactam (4.5 g, every 6 h and every 8 h, 30 min infusion) and meropenem (1 g, every 8 h, 30 min infusion) in a hollow-fibre infection model over 7 days.

RESULTS

Piperacillin/tazobactam regimens attained ∼4-5 log10 cfu/mL bacterial killing within 24 h and prevented resistance emergence over the experiment against ESBL-producing and non-producing E. coli. However, compared with 8 hourly meropenem, the 6 hourly piperacillin/tazobactam attained ∼1 log10 lower bacterial kill against one of three ESBL-producing E. coli (CTAP#173) but comparable killing for the other two ESBL-producing (CTAP#168 and CTAP#169) and two non-producing E. coli (CTAP#179 and CTAP#180). The 6 hourly piperacillin/tazobactam regimen attained ∼1 log10 greater bacterial kill compared with the 8 hourly regimen against CTAP#168 and CTAP#179 at 24 h.

CONCLUSIONS

Our study suggests piperacillin/tazobactam may be a potential alternative to carbapenems to treat urosepsis caused by ESBL-producing E. coli, although clinical trials with robust design are needed to confirm non-inferiority of outcome.

External Evaluation of Population Pharmacokinetic Models to Inform Precision Dosing of Meropenem in Critically Ill Patients

Routine clinical meropenem therapeutic drug monitoring data can be applied to model-informed precision dosing. The current study aimed to evaluate the adequacy and predictive capabilities of the published models with routine meropenem data and identify the dosing adaptations using a priori and Bayesian estimation. For this, 14 meropenem models for the external evaluation carried out on an independent cohort of 134 patients with 205 meropenem concentrations were encoded in NONMEM 7.3. The performance was determined using: 1) prediction-based and simulation-based diagnostics; and 2) predicted meropenem concentrations by a priori prediction using patient covariates only; and Bayesian forecasting using previous observations. The clinical implications were assessed according to the required dose adaptations using the meropenem concentrations. All assessments were stratified based on the patients with or without continuous renal replacement therapy. Although none of the models passed all tests, the model by Muro et al. showed the least bias. Bayesian forecasting could improve the predictability over an a priori approach, with a relative bias of −11.63–68.89% and −302.96%–130.37%, and a relative root mean squared error of 34.99–110.11% and 14.78–241.81%, respectively. A dosing change was required in 40.00–68.97% of the meropenem observation results after Bayesian forecasting. In summary, the published models couldn’t adequately describe the meropenem pharmacokinetics of our center. Although the selection of an initial meropenem dose with a priori prediction is challenging, the further model-based analysis combining therapeutic drug monitoring could be utilized in the clinical practice of meropenem therapy.

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.

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).

Population pharmacokinetics of meropenem in critically ill infant patients

BACKGROUND

Population pharmacokinetic analysis in critically ill infants remains a challenge for lack of information.

OBJECTIVES

To determine the population pharmacokinetic parameters of meropenem and evaluate the covariates affecting population pharmacokinetic parameters.

METHODS

A prospective study was conducted on 35 patients. A total of 160 blood samples were collected and determined free of drug concentrations of meropenem. Population pharmacokinetic data were analyzed using NONMEM software. Internal validation methods, including bootstrapping and prediction-corrected visual predictive checks, were applied to evaluate the robustness and predictive power of the final model.

RESULTS

A one-compartment model with first-order elimination showed the best fit to the data. The typical clearance (CL) values and volume of distribution (V_d) were 1.33 L/h and 2.27 L, respectively. Weight and creatinine clearance were influential covariates for CL, while weight was a significant covariate for V_d of meropenem. The model evaluation results suggested robustness and good predictability of the final model. The standard dosage regimens of meropenem achieved 40% f T_>MIC but not enough if a more aggressive target of 80% f T_>MIC at MIC value of ≥ 16 µg/mL is desired.

CONCLUSIONS

This population pharmacokinetic model could be used for suggesting individualized meropenem dosage regimens in critically ill infants.

Population Pharmacokinetics and Pharmacodynamics of Meropenem in Critically Ill Patients: How to Achieve Best Dosage Regimen According to the Clinical Situation

BACKGROUND AND OBJECTIVES

Meropenem is frequently used for the treatment of severe bacterial infections in critically ill patients. Because critically ill patients are more prone to pharmacokinetic variability than other patients, ensuring an effective blood concentration can be complex. Therefore, describing this variability to ensure a proper use of this antibiotic drug limits the rise and dissemination of antimicrobial resistance, and helps preserve the current antibiotic arsenal. The aims of this study were to describe the pharmacokinetics of meropenem in critically ill patients, to identify and quantify the patients' characteristics responsible for the observed pharmacokinetic variability, and to perform different dosing simulations in order to determine optimal individually adapted dosing regimens.

METHODS

A total of 58 patients hospitalized in the medical intensive care unit and receiving meropenem were enrolled, including 26 patients with renal replacement therapy. A population pharmacokinetic model was developed (using NONMEM software) and Monte Carlo simulations were performed with different dosing scenarios (bolus-like, extended, and continuous infusion) exploring the impact of clinical categories of residual diuresis (anuria, oliguria, and preserved diuresis) on the probability of target attainment (MIC: 1-45 mg/L).

RESULTS

The population pharmacokinetic model included five covariates with a significant impact on clearance: glomerular filtration rate, dialysis (continuous and semi-continuous), renal function status, and volume of residual diuresis. The clearance for a typical patient in our population is 4.20 L/h and volume of distribution approximately 44 L. Performed dosing regimen simulations suggested that, for equivalent doses, the continuous infusion mode (with loading dose) allowed the obtaining of the pharmacokinetic/pharmacodynamic target for a larger number of patients (100% for MIC ≤ 20 mg/L). Nevertheless, for the treatment of susceptible bacteria (MIC ≤ 2 mg/L), differences in the probability of target attainment between bolus-like, extended, and continuous infusions were negligible.

CONCLUSIONS

Identified covariates in the model are easily accessible information in patient health records. The model highlighted the importance of considering the patient's overall condition (renal function and dialysis) and the pathogen's characteristics (MIC target) during the establishment of a patient's dosing regimen.

Pharmacokinetics of Non-β-Lactam β-Lactamase Inhibitors

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

Pharmacokinetics and pharmacodynamics of antibiotics in cystic fibrosis: a narrative review

Cystic fibrosis affects several organs, predisposing patients to severe bacterial respiratory infections, including those caused by methicillin-resistant Staphylococcus aureus. Cystic fibrosis is also associated with a wide spectrum of pathological changes that can significantly affect the absorption, distribution, metabolism, and/or elimination of several drugs, including antibacterial agents. Therefore, awareness of the pharmacokinetic derangements in patients with cystic fibrosis is mandatory for the optimisation of antibiotic therapy. This review discusses the basic principles of pharmacokinetics and the pathophysiology of the pharmacokinetics changes associated with cystic fibrosis; it also provides an update of available data for the most widely used antibiotics. Evidence accumulated in the last few years has clearly shown that a significant number of cystic fibrosis patients treated with conventional dosing schemes have sub-therapeutic antibiotic concentrations, increasing their risk of therapeutic failure and/or the emergence of resistant pathogens. Some proposals to optimise antibiotic therapies in this clinical setting based on therapeutic drug monitoring are also discussed.

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.

Evaluation of the MeroRisk Calculator, A User-Friendly Tool to Predict the Risk of Meropenem Target Non-Attainment in Critically Ill Patients

BACKGROUND

The MeroRisk-calculator, an easy-to-use tool to determine the risk of meropenem target non-attainment after standard dosing (1000 mg; q8h), uses a patient's creatinine clearance and the minimum inhibitory concentration (MIC) of the pathogen. In clinical practice, however, the MIC is rarely available. The objectives were to evaluate the MeroRisk-calculator and to extend risk assessment by including general pathogen sensitivity data.

METHODS

Using a clinical routine dataset (155 patients, 891 samples), a direct data-based evaluation was not feasible. Thus, in step 1, the performance of a pharmacokinetic model was determined for predicting the measured concentrations. In step 2, the PK model was used for a model-based evaluation of the MeroRisk-calculator: risk of target non-attainment was calculated using the PK model and agreement with the MeroRisk-calculator was determined by a visual and statistical (Lin's concordance correlation coefficient (CCC)) analysis for MIC values 0.125-16 mg/L. The MeroRisk-calculator was extended to include risk assessment based on EUCAST-MIC distributions and cumulative-fraction-of-response analysis.

RESULTS

Step 1 showed a negligible bias of the PK model to underpredict concentrations (-0.84 mg/L). Step 2 revealed a high level of agreement between risk of target non-attainment predictions for creatinine clearances >50 mL/min (CCC = 0.990), but considerable deviations for patients <50 mL/min. For 27% of EUCAST-listed pathogens the median cumulative-fraction-of-response for the observed patients receiving standard dosing was < 90%.

CONCLUSIONS

The MeroRisk-calculator was successfully evaluated: For patients with maintained renal function it allows a reliable and user-friendly risk assessment. The integration of pathogen-based risk assessment substantially increases the applicability of the tool.

Model-Informed Therapeutic Drug Monitoring of Meropenem in Critically Ill Patients: Improvement of the Predictive Ability of Literature Models with the PRIOR Approach

BACKGROUND AND OBJECTIVE

To improve the predictive ability of literature models for model-informed therapeutic drug monitoring (TDM) of meropenem in intensive care units, we propose to tweak the literature models with the "prior approach" using a subset of the data. This study compares the predictive ability of both literature and tweaked models on TDM concentrations of meropenem in critically ill patients.

METHODS

Blood samples were collected from patients of an intensive care unit treated with intravenous meropenem. Data were split six times into an "estimation" and a "prediction" datasets. Population pharmacokinetic (popPK) models of meropenem were selected from literature. These models were run on the "estimation" dataset with the $PRIOR subroutine in NONMEM to obtain tweaked models. The literature and tweaked models were used a priori (with covariate only) and with Bayesian fitting to predict each individual concentration from the previous concentration(s). Their respective predictive abilities were compared using median relative prediction error (MDPE%) and median absolute relative prediction error (MDAPE%).

RESULTS

The total dataset was composed of 115 concentrations from 58 patients. For each of the six splits, the "estimation" and the "prediction" datasets were respectively composed of 44 and 14 patients or 45 and 13 patients. Six popPK models were selected in the literature. MDPE% and MDAPE% were globally lower for the tweaked than for the literature models, especially for a priori predictions.

CONCLUSION

The "prior approach" could be a valuable tool to improve the predictive ability of literature models, especially for a priori predictions, which are important to optimize dosing in emergency situations.

Evaluation of pharmacokinetic and pharmacodynamic parameters of meropenem in critically ill patients with acute kidney disease

Purpose

No study has been evaluated pharmacokinetic (PK) and pharmacodynamic (PD) properties of β-lactam antibiotics in patients with acute kidney injury (AKI), not requiring renal replacement therapy (RRT). We evaluated the time that plasma concentrations remain above four times the MIC (ft > 4MIC) and PK parameters of meropenem in this population.

Methods

In this prospective, randomized clinical trial (RCT), all patients received standard dose (3 g daily) of meropenem for 48 h, then randomly allocated in standard or adjusted groups. The standard group received meropenem without dose adjustment. In the adjusted group, the meropenem dose was adjusted based on the Cockcroft-Gault(C-G) equation. Meropenem concentrations were measured at the peak and trough times on the 2nd and 5th days of the study.

Results

On the 2nd day of the study, 3 out of 10 (30%) of patients attained the PD target (≥ 80%ft > 4MIC). In the 5th day of the study, the PD target was attained in 2 out of 10 (20%) and 1 out of 5 (20%) of patients who received standard and adjusted doses of meropenem, respectively (p = 1). In all samples, increased volume of distribution (Vd) (median; IQR) (46.04; 23.06–103.18 L), terminal half-life (T1/2) (4.51; 2.67–8.88 h) and decreased clearance (6.52; 4.43–10.16 L/h) have been shown.

Conclusion

In critically ill patients with AKI, who not receive RRT, standard doses, and adjusted according to renal function of meropenem failed to achieve PD target of ≥ 80%ft > 4MIC. Higher doses are required for this target.

Retrospectively registered

The study protocol with registered retrospectively and approved on January 19, 2019, with the number of IRCT20160412027346N5.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00228-020-03062-0.

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.

Reappraisal of the Optimal Dose of Meropenem in Critically Ill Infants and Children: a Developmental Pharmacokinetic-Pharmacodynamic Analysis

Data of developmental pharmacokinetics (PK) of meropenem in critically ill infants and children with severe infections are limited. We assessed the population PK and defined the appropriate regimen to optimize treatment in this population based on developmental PK-pharmacodynamic (PD) analysis. Blood samples were collected from pediatric intensive care unit patients with severe infection treated with standard dosage regimens for meropenem. Population PK data were analyzed using NONMEM software. Fifty-seven patients (mean age, 2.96 years [range, 0.101 to 14.4]; mean body weight, 15.8 kg [range, 5.0 to 65.0]) were included. A total of 135 meropenem concentrations were obtainable for population PK modeling. The median number of samples per patients was 2 (range, 1 to 4). A two-compartment model with first-order elimination was optimal for PK modeling. Weight and creatinine clearance (estimated by the Schwartz formula) were significantly correlated with the PK parameters of meropenem. The probabilities of target attainment for pathogens with low MICs of 1 and 2 μg/ml were 87.5% and 68.6% following administration of 40 mg/kg/dose (every 8 h [q8h]) as a 4-h infusion and 98.0% and 73.3% with high MICs of 4 and 8 μg/ml following administration of 110 mg/kg/day as a continuous infusion in critically ill infants and children under 70% fT _>MIC (the free time during which the plasma concentration of meropenem exceeds the MIC), respectively. The standard dosage regimens for meropenem did not meet an appropriate PD target, and an optimal dosing regimen was established in critically ill infants and children. (This study has been registered at ClinicalTrials.gov under identifier NCT03643497.).

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.

Population pharmacokinetics and evaluation of the predictive performance of pharmacokinetic models in critically ill patients receiving continuous infusion meropenem: a comparison of eight pharmacokinetic models

Background

Several population pharmacokinetic (PopPK) models for meropenem dosing in ICU patients are available. It is not known to what extent these models can predict meropenem concentrations in an independent validation dataset when meropenem is infused continuously.

Patients and methods

A PopPK model was developed with concentration-time data collected from routine care of 21 ICU patients (38 samples) receiving continuous infusion meropenem. The predictability of this model and seven other published PopPK models was studied using an independent dataset that consisted of 47 ICU patients (161 samples) receiving continuous infusion meropenem. A statistical comparison of imprecision (mean square prediction error) and bias (mean prediction error) was conducted.

Results

A one-compartment model with linear elimination and creatinine clearance as a covariate of clearance best described our data. The mean ± SD parameter estimate for CL was 9.89 ± 3.71 L/h. The estimated volume of distribution was 48.1 L. The different PopPK models showed a bias in predicting serum concentrations from the validation dataset that ranged from -8.76 to 7.06 mg/L. Imprecision ranged from 9.90 to 42.1 mg/L.

Conclusions

Published PopPK models for meropenem vary considerably in their predictive performance when validated in an external dataset of ICU patients receiving continuous infusion meropenem. It is necessary to validate PopPK models in a target population before implementing them in a therapeutic drug monitoring program aimed at optimizing meropenem dosing.

Diagnostic and medical needs for therapeutic drug monitoring of antibiotics

Therapeutic drug monitoring (TDM) of antibiotics has been practiced for more than half a century, but it is still not widely applied for infected patients. It has a traditional focus on limiting toxicity of specific classes of antibiotics such as aminoglycosides and vancomycin. With more patients in critical care with higher levels of sickness severity and immunosuppression as well as an increasingly obese and ageing population, an increasing risk of suboptimal antibiotic exposure continues to escalate. As such, the value of TDM continues to expand, especially for beta-lactams which constitute the most frequently used antibiotic class. To date, the minimum inhibitory concentration (MIC) of infectious microbes rather than classification in terms of susceptible and resistant can be reported. In parallel, increasingly sophisticated TDM technology is becoming available ensuring that TDM is feasible and can deliver personalized antibiotic dosing schemes. There is an obvious need for extensive studies that will quantify the improvements in clinical outcome of individual TDM-guided dosing. We suggest that a broad diagnostic and medical investigation of the TDM arena, including market analyses and analytical technology assessment, is a current priority.

Using machine learning to optimize antibiotic combinations: dosing strategies for meropenem and polymyxin B against carbapenem-resistant Acinetobacter baumannii

OBJECTIVES

Increased rates of carbapenem-resistant strains of Acinetobacter baumannii have forced clinicians to rely upon last-line agents, such as the polymyxins, or empirical, unoptimized combination therapy. Therefore, the objectives of this study were: (a) to evaluate the in vitro pharmacodynamics of meropenem and polymyxin B (PMB) combinations against A. baumannii; (b) to utilize a mechanism-based mathematical model to quantify bacterial killing; and (c) to develop a genetic algorithm (GA) to define optimal dosing strategies for meropenem and PMB.

METHODS

A. baumannii (N16870; MIC_meropenem = 16 mg/L, MIC_PMB = 0.5 mg/L) was studied in the hollow-fibre infection model (initial inoculum 10⁸ cfu/mL) over 14 days against meropenem and PMB combinations. A mechanism-based model of the data and population pharmacokinetics of each drug were used to develop a GA to define the optimal regimen parameters.

RESULTS

Monotherapies resulted in regrowth to ~10¹⁰ cfu/mL by 24 h, while combination regimens employing high-intensity PMB exposure achieved complete bacterial eradication (0 cfu/mL) by 336 h. The mechanism-based model demonstrated an SC₅₀ (PMB concentration for 50% of maximum synergy on meropenem killing) of 0.0927 mg/L for PMB-susceptible subpopulations versus 3.40 mg/L for PMB-resistant subpopulations. The GA had a preference for meropenem regimens that improved the %T > MIC via longer infusion times and shorter dosing intervals. The GA predicted that treating 90% of simulated subjects harbouring a 10⁸ cfu/mL starting inoculum to a point of 10⁰ cfu/mL would require a regimen of meropenem 19.6 g/day 2 h prolonged infusion (2 hPI) q5h + PMB 5.17 mg/kg/day 2 hPI q6h (where the 0 h meropenem and PMB doses should be 'loaded' with 80.5% and 42.2% of the daily dose, respectively).

CONCLUSION

This study provides a methodology leveraging in vitro experimental data, a mathematical pharmacodynamic model, and population pharmacokinetics provide a possible avenue to optimize treatment regimens beyond the use of the 'traditional' indices of antibiotic action.

Bio-analytical methods for investigating the effect of age, body mass index and gender on the PK/PD ratio of antibiotics

The effectiveness of antibiotics (ABs) is governed by achieving the adequate pharmacokinetic (PK)/pharmacodynamics (PD) ratio. In this study, fast LC-MS/MS methods were developed and validated for the bioanalysis of cefaclor (CFC), ciprofloxacin (CFC), roxithomycin (RXM) and clindamycin (CLD). Chromatographic separation was performed on a C₁₈ Zorbax-Eclipse Plus (3.5 μm, 100 × 4.6 mm) using isocratic elution. Detection was performed by positive electrospray ionization. The methods were applied for the assessment of PK parameters in volunteers (n = 101, 64 male and 37 female) and the effects of age, body mass index (BMI) and gender were investigated. Good linearity (r² ≥ 0.99), accuracy (>86%), precision (CV% ≤ 11) and extraction recovery (>83%) were observed for CFC, CFX, RXM and CLD. Application to PK studies revealed that age and BMI affected the T_half and the AUC of RXM and CLD (p < 0.023). Gender difference affected the critical PK parameters of the four ABs (T_half (U = 18; P = 0.036) of CFC, the C_max of CFX (U = 30; P = 0.017), the T_half (U = 23; P = 0.009) and AUC (U = 26; P = 0.008) of RXM and CLD), respectively. These results highlight the significance of age and BMI variations for RXM and CLD dosing. Furthermore, it indicates that the gender difference may be considered when adjusting the AB dose.

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.

Pharmacodynamic model for β-lactam regimens used in surgical prophylaxis: model-based evaluation of standard dosing regimens

Background Continual evolution of resistance among bacteria against methods of surgical prophylaxis may make currently used beta-lactam regimens inadequate. Objective To re-evaluate beta-lactam regimens in surgical prophylaxis. Setting A pharmacodynamic Monte Carlo simulation (MCS) model based on a number of patients in China. Methods Pharmacodynamic profiling using Monte Carlo simulation up to 4 hours postinfusion was conducted for standard-dose, short-term (0.5 h) and prolonged (2 to 4 h) infusions of ampicillin, cefazolin, cefotaxime, cefoxitin, cefuroxime, ertapenem, and piperacillin/tazobactam in adult patients with normal renal function. Microbiological data were incorporated. Cumulative fraction of response (CFR) was determined for each regimen against populations of S. aureus, coagulase-negative staphylococci and E. coli. The optimal CFR was defined as ≥ 90% response. Main Outcome Measure Cumulative fractions of response of pharmacodynamic target attainment. Results During the first 2 hours postinfusion, piperacillin/tazobactam 3.375 g exhibited consistently optimal cumulative fractions against S. aureus, CoNS and E. coli. Ampicillin 2 g (2 h) also displayed optimal CFRs for S. aureus and E. coli but not for coagulase-negative staphylococci. Cefoxitin 2 g didnot achieve any optimal CFRs, even via 2-h prolonged infusion (maximum 72.8% CFR for S. aureus and 64.5% CFR for E. coli). Cefazolin 2 g (4 h) and cefuroxime 1.5 g (4 h) provided desired CFRs across 4 h postinfusion for S. aureus but provided poor CFRs for coagulase-negative staphylococci and E. coli. Only ertapenem 1 g for E. coli and S. aureus and cefotaxime 1 g for E. coli consistently yielded ≥ 90% CFRs for 4 hour postinfusion. Conclusions Certain dosing regimens may warrant adjustment for improved prevention efficiency and enhanced empirical antibiotic regimens for surgical prophylaxis.

Population Pharmacokinetic Analysis of Meropenem After Intravenous Infusion in Korean Patients With Acute Infections

PURPOSE

The aim of this study was to investigate the population pharmacokinetic (PK) profile of meropenem in Korean patients with acute infections.

METHODS

The study included 37 patients with a creatinine clearance ≤50 or >50 mL/min who received a 500- or 1000-mg dose of meropenem, respectively, infused intravenously over 1 hour every 8 hours. Blood samples were collected before and at 1, 1.5, and 5 hours after the start of the fourth infusion. The population PK analysis was conducted by using nonlinear mixed effect modeling software (NONMEM). Monte-Carlo simulations were performed to identify optimal dosing regimens.

FINDINGS

Thirty-seven subjects completed the study. Meropenem PK variables were well described by using a one-compartment model. The typical values (relative SE) for weight-normalized clearance (CL) and V_d were 0.266 L/h/kg (12.29%) and 0.489 L/kg (11.01%), respectively. Meropenem CL was significantly influenced by the serum creatinine level, which explained 11% of the interindividual CK variability. The proposed equation to estimate meropenem CL in Korean patients was as follows: CL (L/h) = 0.266 × weight × [serum creatinine/0.74]^-1.017_. The simulation results indicate that the current meropenem dosing regimen may be suboptimal in patients infected with normal or augmented renal function.

IMPLICATIONS

Prolonged infusions of meropenem over at least 2 hours should be considered, especially in patients with augmented renal function and those infected with pathogens for which the minimum inhibitory meropenem concentration is >1 μg/mL. Our results suggest an individualized meropenem dosing regimen for patients with abnormal renal function and those infected with pathogens with decreased in vitro susceptibility.

Clinical outcomes of prolonged infusion (extended infusion or continuous infusion) versus intermittent bolus of meropenem in severe infection: A meta-analysis

Background

Meropenem exhibits time-dependent antimicrobial activity and prolonged infusion (PI) (extended infusion or continuous infusion, EI or CI) of meropenem can better achieve pharmacodynamics target when comparing with intermittent bolus (IB). However, the clinical outcomes between two groups remain inconclusive.

Objective

To evaluate current published literatures by meta-analysis to ascertain whether PI of meropenem can improve clinical outcomes.

Methods

Medline, Cochrane database and EMBASE were searched. Randomized control trails (RCT) and observational studies which compared the clinical outcomes of PI and IB groups were included and evaluated for quality. The data of studies were extracted and meta-analysis was performed using Revman 5.3 software.

Results

Six RCTs and 4 observation studies with relatively high quality were included in this analysis. Compared to IB group, PI group had a higher clinical success rate (odd ratio 2.10, 95% confidence interval 1.31–3.38) and a lower mortality (risk ratio 0.66, 95% confidence interval 0.50–0.88). The sensitivity analysis showed the results were stable.

Conclusion

PI of meropenem was associated with a higher clinical improvement rate and a lower mortality. It is recommended for patients with severe infection or infected by less sensitive microbial.

KPC-producing Klebsiella pneumoniae bloodstream isolates from Brazilian hospitals: What (still) remains active?

OBJECTIVES

This study assessed susceptibility to polymyxin B (PMB) and alternative antimicrobials, with focus on aminoglycosides and tigecycline, according to different breakpoints in KPC-producing Klebsiella pneumoniae (KPC-Kp) bloodstream isolates from Brazilian hospitals.

METHODS

Bloodstream K. pneumoniae isolates non-susceptible to any of the three carbapenems (meropenem, imipenem or ertapenem) from four Brazilian tertiary-care hospitals were selected. Antimicrobial susceptibility was determined and interpreted according to distinct breakpoints. Twenty-nine PMB-resistant KPC-Kp isolates were selected for molecular typing.

RESULTS

A total of 158 KPC-Kp were analysed. MIC_50/90 values for PMB were 0.25/16mg/L; 40 isolates (25.3%) were resistant to PMB. MIC_50/90 values for meropenem were 32/≥256mg/L; no isolates were susceptible to meropenem according to CLSI, but 10 isolates were intermediate using EUCAST breakpoints (1, MIC=4mg/L; 9, MIC=8mg/L). MIC_50/90 values for tigecycline were 2/8mg/L; 53 (33.5%) and 94 (59.5%) isolates were susceptible according to EUCAST and FDA breakpoints, respectively. MIC_50/90 values were 32/≥64mg/L for amikacin and ≥16/≥16mg/L for gentamicin; 48 (30.4%), 28 (17.7%) and 16 (10.1%) were susceptible to amikacin according to CLSI, EUCAST and USCAST, respectively, but susceptibility rates to gentamicin were <7.0%. Eighteen distinct clonal profiles were identified among 29 PMB-resistant isolates by DNA macrorestriction. Most clones belonged to CC11.

CONCLUSION

Elevated rates of PMB-resistant KPC-Kp bloodstream infections were found in four Brazilian hospitals, mostly of polyclonal origin. Alternative antimicrobials with the highest in vitro activity were tigecycline and amikacin, although susceptibility rates significantly decreased using criteria with stricter breakpoints (e.g. EUCAST, USCAST).