Meropenem Population Pharmacokinetics and Dosing Regimen Optimization in Critically Ill Children Receiving Continuous Renal Replacement Therapy.

BACKGROUND AND OBJECTIVE: We aimed to develop a meropenem population pharmacokinetic model in critically ill children receiving continuous renal replacement therapy and simulate dosing regimens to optimize patient exposure. METHODS: Meropenem plasma concentration was quantified by high-performance liquid chromatography. Meropenem pharmacokinetics was investigated using a non-linear mixed-effect modeling approach. Monte Carlo simulations were performed to compute the optimal scheme of administration, according to the target of a 100% inter-dose interval time in which concentration is one to four times above the minimum inhibitory concentration (100% fT>1-4×MIC). RESULTS: A total of 27 patients with a median age of 4 [interquartile range 0-11] years, a median body weight of 16 [range 7-35] kg receiving continuous renal replacement therapy were included. Concentration-time courses were best described by a one-compartment model with first-order elimination. Body weight (BW) produced significant effects on volume of distribution (V) and BW and continuous renal replacement therapy effluent flow rate (Qeff) produced significant effects on clearance (CL): [Formula: see text] and [Formula: see text], where Vpop and CLpop estimates were 32.5 L and 5.88 L/h, respectively, normalized to a 70-kg BW and median Qeff at 1200 mL/h. Using this final model and Monte Carlo simulations, for patients with Qeff over 1200 mL/h, meropenem continuous infusion was adequate in most cases to attain 100% fT>1-4xMIC. For bacterial infections with a low minimum inhibitory concentration (≤2 mg/L), meropenem intermitent administration was appropriate for patients weighing more than 20 kg with Qeff <500 mL/h and for patients weighing more than 10 kg with Qeff <100 mL/h. CONCLUSIONS: Meropenem exposure in critically ill children receiving continuous renal replacement therapy needs dosing adjustments to the minimum inhibitory concentration that take into account body weight and the continuous renal replacement therapy effluent flow rate.

Population Pharmacokinetic Meta-Analysis and Dosing Recommendation for Meropenem in Critically Ill Patients Receiving Continuous Renal Replacement Therapy.

The optimal dosing regimen for meropenem in critically ill patients undergoing continuous renal replacement therapy (CRRT) remains undefined due to small studied sample sizes and uninformative pharmacokinetic (PK)/pharmacodynamic (PD) analyses in reported studies. The present study aimed to perform a population PK/PD meta-analysis of meropenem using available literature data to suggest the optimal treatment regimen. A total of 501 meropenem concentration measurements from 78 adult CRRT patients pooled from nine published studies were used to develop the population PK model for meropenem. PK/PD target (40% and 100% of the time with the unbound drug plasma concentration above the MIC) marker-based efficacy and risk of toxicity (trough concentrations of >45 mg/L) for short-term (30 min), prolonged (3 h), and continuous (24 h) infusion dosing strategies for meropenem were investigated. The impact of CRRT dose and identified covariates on the PD probability of target attainment (PTA) and predicted toxicity was also examined. Meropenem concentration data were adequately described by a two-compartment model with linear elimination. Trauma was identified as a pronounced modifier for endogenous clearance of meropenem. Simulations demonstrated that adequate PK/PD targets and low risk of toxicity could be achieved in non-trauma CRRT patients receiving meropenem regimens of 1 g every 6 h infused over 30 min, 1 g every 8 h infused over 3 h, and 2 to 4 g every 24 h infused over 24 h. The impact of CRRT dose (25 to 50 mL/kg/h) on PTA was clinically irrelevant, and continuous infusion of 3 to 4 g every 24 h was suitable for trauma CRRT patients (MICs of ≤0.5 mg/L). A population PK model was developed for meropenem in CRRT patients, and different dosing regimens were proposed for non-trauma and trauma CRRT patients.

Therapeutic Target Attainment of 3-Hour Extended Infusion of Meropenem in Patients With Septic Burns.

PURPOSE: The aim of this prospective cohort study was to evaluate the therapeutic target attainment of 3-hour extended infusion of meropenem in patients with septic burns in the early and late periods of septic shock. METHODS: Meropenem serum levels were determined by liquid chromatography from blood samples collected within 48 hours (early period) of therapy and 10 to 14 days afterward (late period). Pharmacokinetic properties were investigated by noncompartmental analysis, and the therapeutic target was defined as 100% of the time above the MIC (100%fT> MIC). FINDINGS: Fifteen patients with 90 measured meropenem concentrations were included. Throughout the entire course of antimicrobial therapy, the therapeutic target was attained against gram-negative pathogens with an MIC ≤ 2 mg/L. Pathogens with intermediate susceptibility to meropenem were only covered in the early phase of therapy. IMPLICATIONS: Higher-dose regimens or continuous infusions may be necessary to guarantee antimicrobial coverage of meropenem against less sensitive pathogens in patients with septic burns.

Combination of Pharmacokinetic and Pathogen Susceptibility Information To Optimize Meropenem Treatment of Gram-Negative Infections in Critically Ill Patients.

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. 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 MIC distribution, stochastic simulations (n = 1,000) of an evaluated pharmacokinetic meropenem model, and a defined pharmacokinetic/pharmacodynamic target (100%T>4×MIC while minimum concentrations were <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 of >90% was considered adequate. The observed MIC distribution significantly differed from the EUCAST database. Based on the 6,520 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. 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.

Optimal loading dose of meropenem before continuous infusion in critically ill patients: a simulation study.

The aim of this study was to investigate optimal loading doses prior to continuous infusion of meropenem in critically ill patients. A previously published and successfully evaluated pharmacokinetic model of critically ill patients was used for stochastic simulations of virtual patients. Maintenance doses administered as continuous infusion of 1.5-6 g/24 h with preceding loading doses (administered as 30 min infusion) of 0.15-2 g were investigated. In addition to the examination of the influence of individual covariates, a best-case and worst-case scenario were simulated. Dosing regimens were considered adequate if the 5th percentile of the concentration-time profile did not drop at any time below four times the S/I breakpoint (= 2 mg/L) of Pseudomonas aeruginosa according to the EUCAST definition. Low albumin concentrations, high body weight and high creatinine clearances increased the required loading dose. A maximum loading dose of 0.33 g resulted in sufficient plasma concentrations when only one covariate showed extreme values. If all three covariates showed extreme values (= worst-case scenario), a loading dose of 0.5 g was necessary. Higher loading doses did not lead to further improvements of target attainment. We recommend the administration of a loading dose of 0.5 g meropenem over 30 min immediately followed by continuous infusion.

Glutathione-Conjugated Hydrogels: Flexible Vehicles for Personalized Treatment of Bacterial Infections.

PURPOSE: Skin and soft tissue infections are increasingly prevalent and often complicated by potentially fatal therapeutic hurdles, such as poor drug perfusion and antibiotic resistance. Delivery vehicles capable of versatile loading may improve local bioavailability and minimize systemic toxicities yet such vehicles are not clinically available. Therefore, we aimed to expand upon the use of glutathione-conjugated poly(ethylene glycol) GSH-PEG hydrogels beyond protein delivery and evaluate the ability to deliver traditional therapeutic molecules. METHODS: PEG and GSH-PEG hydrogels were prepared using ultraviolet light (UV)-polymerization. Hydrogel loading and release of selected drug candidates was examined using UV-visible spectrometry. Therapeutic molecules and GST-fusion protein loading was examined using UV-visible and fluorescent spectrometry. Efficacy of released meropenem was assessed against meropenem-sensitive and -resistant P. aeruginosa in an agar diffusion bioassay. RESULTS: For all tested agents, GSH-PEG hydrogels demonstrated time-dependent loading whereas PEG hydrogels did not. GSH-PEG hydrogels released meropenem over 24 h. Co-loading of biologic and traditional therapeutics into a single vehicle was successfully demonstrated. Meropenem-loaded GSH-PEG hydrogels inhibited the growth of meropenem-sensitive and resistant P. aeruginosa isolates. CONCLUSION: GSH ligands within GSH-PEG hydrogels allow loading and effective delivery of charged therapeutic agents, in addition to biologic therapeutics.

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

WHAT IS KNOWN AND OBJECTIVE: Meropenem, a carbapenem antibiotic, is widely prescribed for the treatment of life-threatening infections. The main parameter associated with its therapeutic success is the percentage of time that the levels remain above the minimum inhibitory concentration. Inadequate levels of meropenem can lead to therapeutic failure and increase the possibility of microbial resistance. The employment of strategies involving dose regimens and drug pharmacodynamics has become increasingly important to optimize therapies. In the present study, we conducted a review with the purpose of assembling information about the clinical use of meropenem and therapeutic drug monitoring. METHODS: A literature review emphasizing the application of therapeutic drug monitoring (TDM) of meropenem in clinical practice has been done. To identify articles related to the topic, we performed a standardized search from January 21, 2020 to December 21, 2020, using specific descriptors in PubMed, Lilacs and Embase. RESULTS AND DISCUSSION: In total, 35 studies were included in the review. The daily dose of meropenem commonly ranged from 3 to 6 g/day. Critically ill patients and those with impaired renal function appear to be the most suitable patients for the application of meropenem TDM, in order to guide therapy. We observed that most of the studies recommend TDM and that, in nine locations, the TDM of meropenem and of other beta-lactams is a routine practice. TDM data can help to maximize the clinical outcomes of the treatment with meropenem. It can also improve the patient care by providing suitable levels of meropenem, guiding the most appropriate dose regimens, which is the main parameter associated with therapeutic success. WHAT IS NEW AND CONCLUSION: The findings from this review suggest that the therapeutic monitoring of meropenem can be beneficial, since it adjusts the treatment and aids clinical outcomes. It does so by indicating the appropriate dosage and preventing failure, toxicity and possible antimicrobial resistance. The multidisciplinary effort, basic knowledge and communication among the medical team are also essential.

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.

Pharmacodynamic Analysis of Meropenem and Fosfomycin Combination Against Carbapenem-Resistant Acinetobacter baumannii in Patients with Normal Renal Clearance: Can It Be a Treatment Option?

Background and Objective: Combination therapy may be a treatment option against carbapenem-resistant Acinetobacter baumannii (CR-AB) infections. In this study, we explored the utility of fosfomycin in combination with meropenem (FOS/MEM) against CR-AB isolates. Materials and Methods: Screening of synergistic activity of FOS/MEM was performed using the checkerboard assay. A pharmacokinetic/pharmacodynamic analysis was performed for various FOS/MEM regimens using Monte Carlo simulations. Results: The minimum inhibitory concentration (MIC) required to inhibit the growth of 50% of the isolates (MIC50) and MIC required to inhibit the growth of 90% of the isolates (MIC90) of FOS and MEM were reduced fourfold and twofold, respectively. The combination was synergistic against 14/50 isolates. No antagonism was observed. Sixteen out of fifty isolates had MEM MICs of ≤8 mg/L when subjected to combination therapy, compared to none with monotherapy. Forty-one out of 50 isolates had FOS MICs of ≤128 mg/L when subjected to combination therapy, compared to 17/50 isolates with monotherapy. The cumulative fraction response for MEM and FOS improved from 0% to 40% and 40% to 80%, with combination therapy, respectively. Conclusions: Addition of MEM improved the in vitro activity of FOS against the CR-AB isolates. FOS/MEM could be a plausible option to treat CR-AB for a small fraction of isolates.

Optimal Dosing of Meropenem in a Small Cohort of Critically Ill Children Receiving Continuous Renal Replacement Therapy.

Severe sepsis is an important cause of mortality and morbidity in critically ill children. Meropenem is a broad-spectrum antibiotic commonly used to treat sepsis. Current meropenem dosage recommendations for children on continuous renal replacement therapy are extrapolated from pharmacokinetic (PK) studies done in adults. Our study aims to determine the optimal dosing in critically ill septic children receiving continuous renal replacement therapy. A prospective single-center PK study was performed in 9 children in the intensive care unit on continuous renal replacement therapy. Meropenem concentrations were measured from blood and effluent fluid samples. A population PK model was developed using nonlinear mixed-effects modeling software (NONMEM, AstraZeneca UK Ltd, Cheshire, UK). Monte Carlo simulations were performed. The PK/pharmacodynamic target aimed for plasma concentrations above minimum inhibitory concentration of 4 mg/L for 100% of dosing interval (100%ƒT>MIC ). A 2-compartment model best characterized meropenem PK. Mean (range) clearance and elimination half-life was 0.091 L/h/kg (0.04-0.157) and 3.9 hours (2.1-7.5), respectively. Dosing of 40 mg/kg/dose every 12 hours over 30 minutes achieved PK/PD target in only 32% while 20 mg/kg every 8 hours over 4 hours or 40 mg/kg every 8 hours over 2 hours achieved 100% ƒT>MIC target for at least 90% of simulated patients.

Efficacy of generic meropenem products in combination with colistin in carbapenemase-producing Klebsiella pneumoniae experimental osteomyelitis.

Guidelines for the management of carbapenemase-producing Enterobacterales (CPE) infections recommend a combination of two active agents, including meropenem if the minimum inhibitory concentration (MIC) is ≤8 mg/L. The therapeutic equivalence of meropenem generics has been challenged. We compared the bactericidal activity of meropenem innovator (AstraZeneca) and four generic products (Actavis, Kabi, Mylan and Panpharma), both in vitro and in vivo, in association with colistin. In vitro time-kill studies were performed at 4 × MIC. An experimental model of KPC-producing Klebsiella pneumoniae osteomyelitis was induced in rabbits by tibial injection of a sclerosing agent followed by 2 × 108 CFU of K. pneumoniae KPC-99YC (meropenem MIC = 4 mg/L; colistin MIC = 1 mg/L). At 14 days after inoculation, treatment for 7 days started in seven groups of ≥10 rabbits, including a control group, a colistin group, and one group for each meropenem product (i.e. the innovator and four generics), in combination with colistin. In vitro, meropenem + colistin was bactericidal with no viable bacteria after 6 h, and this effect was similar with all meropenem products. In the osteomyelitis model, there was no significant difference between meropenem generics and the innovator when combined with colistin. Colistin-resistant strains were detected after treatment with colistin + meropenem innovator (n = 3) and generics (n = 3). The efficacy of four meropenem generics did not differ from the innovator in vitro and in an experimental rabbit model of KPC-producing K. pneumoniae osteomyelitis in terms of bactericidal activity and the emergence of resistance.

Meropenem dosing recommendations for critically ill patients receiving continuous renal replacement therapy.

PURPOSES: To gather available meropenem pharmacokinetics and define drug dosing regimens for Asian critically ill patients receiving CRRT. METHODS: All necessary pharmacokinetic and pharmacodynamic data from Asian population were gathered to develop mathematic models with first order elimination. Meropenem concentration-time profiles were calculated to evaluate efficacy based on the probability of target attainment (PTA) of 40%fT>4MIC. A group of 5000 virtual patients was created and tested using Monte Carlo simulations for each dose in the models. The optimal dosing regimens were defined as the doses achieved at least 90% of the PTA. RESULTS: The recommended meropenem dosing regimen for Asian critically ill patients receiving CRRT with standard (20-25 mL/kg/h) and high (35 mL/kg/h) effluent rates was 750 mg q 8 h to manage Gram negative infections with expected MIC < 2 mg/L in virtual Asian patients. Some meropenem dosages from available clinical resources could not achieve the aforementioned target. The volume of distribution, body weights and nonrenal clearance significantly contributed to drug dosing adaptation especially in the specific population. CONCLUSIONS: A meropenem regimen of 750 mg q 8 h was recommended for Asian critically ill patients receiving 2 different CRRT modalities with standard and high effluent rates. Clinical validation of these results is needed.

Pharmacokinetics of meropenem in burn patients with infections caused by Gram-negative bacteria: Are we getting close to the right treatment?

OBJECTIVES: Infections caused by multidrug-resistant Gram-negative bacteria are associated with high mortality. A relevant concern is the efficacy of antibiotic therapy in burn patients in whom pathophysiological changes strongly influence pharmacokinetic (PK) parameters. This study aimed to describe the PK parameters of meropenem in a population of burn patients. METHODS: Blood samples were collected immediately before and 2 h and 5 h after the start of intravenous drug administration. Plasma meropenem concentrations were determined using an ultra-performance liquid chromatography-photodiode array method. RESULTS: Seventeen burn patients were enrolled in the study. Thirteen patients (76%) were treated with meropenem for infections byPseudomonas aeruginosa or Acinetobacter baumannii isolated from blood or wounds. Mean Cmax, Cmin, AUC0-24, half-life, drug clearance and volume of distribution were 28.9 mg/L, 3.7 mg/L, 280.2 mg h/L, 2.0 h, 19.0 L/h and 44.4 L, respectively. Six patients (35%) achieved a Cmin ≥3.3 mg/L and seven patients (41%) achieved a Cmax ≥ 28.4 mg/L, whilst nine patients (53%) achieved an AUC0-24 of >226 mg h/L. Given a minimum inhibitory concentration (MIC) of 0.5 mg/L, all patients satisfied the target AUC/MIC of >125, but when the MIC rises to 2 mg/L (the ECOFF), only five patients reached the desired AUC/MIC. Regarding fT>MIC at an MIC of 2 mg/L with a 2-h infusion time, 13 patients (76%) achieved the PK target (>75%). CONCLUSION: These data suggest that a combined 2-h infusion with a higher dosage of meropenem, including a loading dose, may be successful to achieve effective PK parameters.

Use of meropenem in treating carbapenem-resistant Enterobacteriaceae infections.

Introduction: The epidemiology of carbapenem-resistant Enterobacterales (CRE) is increasingly worldwide. Production of carbapenemases is the most common and efficient mechanism of carbapenem resistance, and could theoretically be overcome by optimizing the pharmacokinetic/pharmacodynamic (PK/PD) behavior of meropenem. Areas covered: This article overviews the available literature concerning the potential role that meropenem may still have in the treatment carbapenem-resistant Enterobacteriaceae infections. Clinical studies published in English language until June 2019 were searched on PubMed database. Expert commentary: High-dose continuous infusion meropenem-based combination regimens could still represent a valuable option for treating CRE infections in specific circumstances. Knowledge of the local prevalent mechanisms of carbapenem resistance, of patient clinical severity, of the site of infection, of an accurate minimum inhibitory concentration (MIC) value, coupled with the possibility of carrying-out a real-time therapeutic drug monitoring (TDM)-based PK/PD optimization of drug exposure must all be considered as fundamental for properly pursuing this goal.

Relative potency of different generic brands of meropenem, colistin and fosfomycin: Implications for antimicrobial therapy and antimicrobial formulary.

There is a need of a relatively simple and inexpensive method for the determination of relative potency of various generic brands of antibiotics in comparison to original products. The current study describes an agar diffusion method which can be performed in any microbiology laboratory, is cheap (costs $2 per test) and its results can be available after overnight incubation. The results show that neither all generics are reliable nor are all generic antibiotics of poor quality.

OTAC: Optimization of Antibiotic Therapy in Critically ill Patients. Using beta-lactam antibiotics by continuous infusion.

OBJECTIVE: To determine the percentage of patients given standard doses of piperacillin/tazobactam or meropenem by continuous  infusion who achieved the target pharmacokinetic/pharmacodynamic  (PK/PD) index, which was defined as free concentrations four times  more than the minimum inhibitory concentration (CMI) for 100% of the  dosing interval (100% fT≥ 4 x MIC). METHOD: Preliminary data from a larger prospective clinical study  analysing the PK/PD behaviour of ß-lactams antibiotics continuous  infusion (CI) in critical patients. The study was conducted in the  intensive care units of a tertiary university hospital for adults (June  2015-May 2017). Inclusion criteria: normal renal function (glomerular  renal function (GFR) CKD-EPI formula ≥ 60 mL/min/1.73 m2) and  treatment with standard dose ß-lactams CI. Concentrations at steady  state (Css) conditions were determined using UHPLC-MS/MS. We  selected the highest susceptible MIC for all likely organisms according to  European Commitee on Antimicrobial Susceptibility Testing's (i.e.  piperacillin/tazobactam: 8 mg/L for enterobacteriaceae and 16 mg/L for  Pseudomonas aeruginosa; meropenem: 2 mg/L for any  microorganism). In addition, a subanalysis of patients was conducted using actual MIC values. RESULTS: 61 patients were enrolled (25 to meropenem and 36 to  piperacillin/tazobactam). Average age was 59 (15) years and median  GFR rate was 95 mL/min/1.73 m2 (83-115). Median meropenem and  piperacillin free concentrations were 16 mg/L (11-29) and 40 mg/L (21- 51), respectively. 88% of patients treated with meropenem reached the  PK/PD target, without differences between both microorganisms. For  piperacillin/tazobactam, 61% and 11% of patients reached the target,  with enterobacteriaceae and Pseudomonas as suspected  microorganisms, respectively. The pathogen was isolated in 35 (57%)  patients: 94% reached the target PK/PD, without differences between  both antibiotic therapies. CONCLUSIONS: Standard doses of meropenem CI are sufficient to  achieve a PK/PD target of 100% fT≥ 4 x MIC in suspected infections  with high MICs (Pseudomonas aeruginosa or enterobacteriaceae).  However, higher doses of piperacillin/tazobactam could be considered to  achieve this goal. In patients with isolated microorganisms, a  standard dose of both antibiotic therapies would be sufficient to achieve  the target. Therapeutic drug monitoring is highly recommended for  therapeutic optimization.

Objetivo: Determinar el porcentaje de pacientes, a los que se les  administró dosis estándar de piperacilina/tazobactam o meropenem en  perfusión continua, que alcanzaban el índice  farmacocinético/farmacodinámico diana definido como el 100% del  intervalo de administración en que las concentraciones de antibiótico  libre fueron cuatro veces iguales o superiores a la concentración mínima  inhibitoria (100% fT ≥ 4 x CMI).Método: Datos preliminares obtenidos de un estudio clínico prospectivo que analiza el comportamiento  farmacocinético/farmacodinámico de los antibióticos betalactámicos  administrados en perfusión continua en pacientes críticos. Se realizó en  unidades de cuidados intensivos de un hospital universitario de tercer  nivel, desde junio de 2015 a mayo de 2017. Criterios de inclusión:  adultos con función renal correcta (filtrado glomerular según la fórmula  CKD-EPI ≥ 60 ml/min/1,73 m2) y tratados con dosis estándar de  antibióticos betalactámicos en perfusión continua. Las concentraciones  en estado de equilibrio estacionario fueron determinadas mediante  cromatografía líquida acoplada a espectrometría de masas (UHPLC- MS/MS). Se utilizaron valores de concentración mínima  inhibitoria  teóricos para microorganismos más resistentes (piperacilina/ tazobactam: 16 mg/l para Pseudomonas aeruginosa y 8 mg/l para Enterobacteriaceae; meropenem: 2 mg/l, independientemente del  microorganismo). Además, se realizó un subanálisis de los pacientes con aislamiento microbiológico (concentraciones mínimas inhibitorias  reales).Resultados: Se incluyeron 61 pacientes (25 meropenem y 36  piperacilina/ tazobactam). Edad media 59 años (15), mediana de  filtrado glomerular 95 ml/min/1,73 m2 (83-115). Mediana de  concentraciones en estado de equilibrio estacionario libre: 16 mg/l (11- 29) meropenem y 40 mg/l (21-51) piperacilina. El 88% de los pacientes  tratados con meropenem alcanzaron el objetivo  farmacocinético/farmacodinámico, sin diferencias entre Enterobacteriaceae y Pseudomonas. En el caso de  piperacilina/tazobactam, el 61% y el 11% de los pacientes alcanzaron la  diana, considerando Enterobacteriaceae y Pseudomonas como  microorganismo sospechoso. Un total de 35 (57%) pacientes  presentaron aislamiento microbiológico. El 94% de ellos alcanzaron la  diana, sin diferencias entre los dos antibióticos.Conclusiones: Ante la sospecha de infecciones por microorganismos con concentraciones mínimas inhibitorias elevadas  (Pseudomonas aeruginosa o enterobacterias), se observa que dosis  convencionales de meropenem en perfusión continua son suficientes  para lograr la diana 100% fT≥ 4 x MIC. Sin embargo, se requerirían  dosis superiores de piperacilina/tazobactam. En casos de aislamiento  microbiológico, dosis estándar de ambos antibióticos fueron suficientes  para lograr la diana. La monitorización farmacocinética es altamente  recomendable para la optimización terapéutica.

Ex Vivo Characterization of Effects of Renal Replacement Therapy Modalities and Settings on Pharmacokinetics of Meropenem and Vaborbactam.

The combination product meropenem-vaborbactam, with activity against KPC-producing carbapenem-resistant Enterobacteriaceae, is likely to be used during renal replacement therapy. The aim of this work was to describe the extracorporeal removal (adsorption and clearance) of meropenem-vaborbactam during continuous venovenous hemofiltration (CVVH). An ex vivo model was used to examine the effects of a matrix of operational settings. Vaborbactam did not adsorb to AN69 (acrylonitrile and sodium methallylsulfonate copolymer) ST100 (surface area, 1 m2) hemofilter; the mean (±standard deviation [SD]) meropenem adsorption was 9% (±1%). The sieving coefficients (mean ± SD) with AN69 ST100 and ST150 (surface area, 1.5 m2) filters ranged from 0.97 ± 0.16 to 1.14 ± 0.12 and from 1.13 ± 0.01 to 1.53 ± 0.28, respectively, for meropenem and from 0.64 ± 0.39 to 0.90 ± 0.14 and 0.78 ± 0.18 to 1.04 ± 0.28, respectively, for vaborbactam. At identical settings, vaborbactam sieving coefficients were 25% to 30% lower than for meropenem. Points of dilution, blood flow rates, or effluent flow rates did not affect sieving coefficients for either drug. However, doubling the effluent flow rate resulted in >50 to 100% increases in filter clearance for both drugs. Postfilter dilution resulted in 40 to 80% increases in filter clearance at a high effluent flow rate (4,000 ml/h), compared with ∼15% increases at a low effluent flow rate (1,000 ml/h) for both drugs. For all combinations of setting and filters tested, vaborbactam clearance was lower than that of meropenem by ∼20 to 40%. Overall, meropenem-vaborbactam is efficiently cleared in CVVH mode.

Therapeutic drug monitoring of ß-lactam antibiotics in the critically ill: direct measurement of unbound drug concentrations to achieve appropriate drug exposures.

Objectives: To describe the achievement of unbound ß-lactam antibiotic concentration targets in a therapeutic drug monitoring (TDM) programme in critically ill patients, and the factors associated with failure to achieve a target concentration. Patients and methods: Plasma samples and clinical data were obtained for analysis from a single centre prospectively. Unbound concentrations of ceftriaxone, cefazolin, meropenem, ampicillin, benzylpenicillin, flucloxacillin and piperacillin were directly measured using ultracentrifugation. Factors associated with the achievement of pharmacokinetic/pharmacodynamic (PK/PD) targets or negative clinical outcomes were evaluated with binomial logistic regression. Results: TDM data from 330 patients, and 369 infection episodes, were included. The range of doses administered was 99.4% ± 45.1% relative to a standard daily dose. Dose increases were indicated in 33.1% and 63.4% of cases to achieve PK/PD targets of 100% fT>MIC and 100% fT>4×MIC, respectively. Dose reduction was indicated in 17.3% of cases for an upper PK/PD threshold of 100% fT>10×MIC. Higher protein bound ß-lactams (ceftriaxone and benzylpenicillin) had better therapeutic target attainment (P < 0.01), but were prone to excessive dosing. Augmented renal clearance (calculated CLCR >130 mL/min) increased the odds of failure to achieve 100% fT>MIC and 100% fT>4×MIC (OR 2.47 and 3.05, respectively; P < 0.01). Conclusions: Measuring unbound concentrations of ß-lactams as part of a routine TDM programme is feasible and demonstrates that a large number of critically ill patients do not achieve predefined PK/PD targets. The clinical significance of this finding is unknown due to the lack of correlation between PK/PD findings and clinical outcomes.

Activity of Meropenem-Vaborbactam in Mouse Models of Infection Due to KPC-Producing Carbapenem-Resistant Enterobacteriaceae.

Meropenem-vaborbactam (Vabomere) is highly active against Gram-negative pathogens, especially Klebsiella pneumoniae carbapenemase (KPC)-producing, carbapenem-resistant Enterobacteriaceae The objective of these studies was to evaluate the efficacy of meropenem alone and in combination with vaborbactam in mouse thigh and lung infection models. Thighs or lungs of neutropenic mice were infected with KPC-producing carbapenem-resistant Enterobacteriaceae, with meropenem MICs ranging from ≤0.06 to 8 mg/liter in the presence of 8 mg/liter vaborbactam. Mice were treated with meropenem alone or meropenem in combination with vaborbactam every 2 h for 24 h to provide exposures comparable to 2-g doses of each component in humans. Meropenem administered in combination with vaborbactam produced bacterial killing in all strains tested, while treatment with meropenem alone either produced less than 0.5 log CFU/tissue of bacterial killing or none at all. In the thigh model, 11 strains were treated with the combination of meropenem plus vaborbactam (300 plus 50 mg/kg of body weight). This combination produced from 0.8 to 2.89 logs of bacterial killing compared to untreated controls at the start of treatment. In the lung infection model, two strains were treated with the same dosage regimen of meropenem and vaborbactam. The combination produced more than 1.83 logs of bacterial killing against both strains tested compared to untreated controls at the start of treatment. Overall, these data suggest that meropenem-vaborbactam may have utility in the treatment of infections due to KPC-producing carbapenem-resistant Enterobacteriaceae.