A quantitative map of nuclear pore assembly reveals two distinct mechanisms.

Understanding how the nuclear pore complex (NPC) is assembled is of fundamental importance to grasp the mechanisms behind its essential function and understand its role during the evolution of eukaryotes1-4. There are at least two NPC assembly pathways-one during the exit from mitosis and one during nuclear growth in interphase-but we currently lack a quantitative map of these events. Here we use fluorescence correlation spectroscopy calibrated live imaging of endogenously fluorescently tagged nucleoporins to map the changes in the composition and stoichiometry of seven major modules of the human NPC during its assembly in single dividing cells. This systematic quantitative map reveals that the two assembly pathways have distinct molecular mechanisms, in which the order of addition of two large structural components, the central ring complex and nuclear filaments are inverted. The dynamic stoichiometry data was integrated to create a spatiotemporal model of the NPC assembly pathway and predict the structures of postmitotic NPC assembly intermediates.

Engineered HaloTag variants for fluorescence lifetime multiplexing.

Self-labeling protein tags such as HaloTag are powerful tools that can label fusion proteins with synthetic fluorophores for use in fluorescence microscopy. Here we introduce HaloTag variants with either increased or decreased brightness and fluorescence lifetime compared with HaloTag7 when labeled with rhodamines. Combining these HaloTag variants enabled live-cell fluorescence lifetime multiplexing of three cellular targets in one spectral channel using a single fluorophore and the generation of a fluorescence lifetime-based biosensor. Additionally, the brightest HaloTag variant showed up to 40% higher brightness in live-cell imaging applications.

Probing coenzyme A homeostasis with semisynthetic biosensors.

Coenzyme A (CoA) is one of the central cofactors of metabolism, yet a method for measuring its concentration in living cells is missing. Here we introduce the first biosensor for measuring CoA levels in different organelles of mammalian cells. The semisynthetic biosensor is generated through the specific labeling of an engineered GFP-HaloTag fusion protein with a fluorescent ligand. Its readout is based on CoA-dependent changes in Förster resonance energy transfer efficiency between GFP and the fluorescent ligand. Using this biosensor, we probe the role of numerous proteins involved in CoA biosynthesis and transport in mammalian cells. On the basis of these studies, we propose a cellular map of CoA biosynthesis that suggests how pools of cytosolic and mitochondrial CoA are maintained.

A general method for the development of multicolor biosensors with large dynamic ranges.

Fluorescent biosensors enable the study of cell physiology with spatiotemporal resolution; yet, most biosensors suffer from relatively low dynamic ranges. Here, we introduce a family of designed Förster resonance energy transfer (FRET) pairs with near-quantitative FRET efficiencies based on the reversible interaction of fluorescent proteins with a fluorescently labeled HaloTag. These FRET pairs enabled the straightforward design of biosensors for calcium, ATP and NAD+ with unprecedented dynamic ranges. The color of each of these biosensors can be readily tuned by changing either the fluorescent protein or the synthetic fluorophore, which enables simultaneous monitoring of free NAD+ in different subcellular compartments following genotoxic stress. Minimal modifications of these biosensors furthermore allow their readout to be switched to fluorescence intensity, fluorescence lifetime or bioluminescence. These FRET pairs thus establish a new concept for the development of highly sensitive and tunable biosensors.

Towards optimizing cefepime/tazobactam (WCK 4282) exposure to achieve efficacy against piperacillin/tazobactam-resistant ESBL infections: dose recommendations for various renal functions, including intermittent haemodialysis, in healthy individuals.

OBJECTIVES: WCK 4282 is a novel combination of cefepime 2 g and tazobactam 2 g being developed for the treatment of infections caused by piperacillin/tazobactam-resistant ESBL infections. The dosing regimen for cefepime/tazobactam needs to be optimized to generate adequate exposures to treat infections caused by ESBL-producing pathogens resistant to both cefepime and piperacillin/tazobactam. METHODS: We developed pharmacokinetic population models of cefepime and tazobactam to evaluate the optimal dose adjustments in patients, including those with augmented renal clearance as well as various degrees of renal impairment, and also for those on intermittent haemodialysis. Optimal doses for various degrees of renal function were identified by determining the PTA for a range of MICs. To cover ESBL-producing pathogens with an cefepime/tazobactam MIC of 16 mg/L, a dosing regimen of 2 g q8h infused over 1.5 h resulted in a combined PTA of 99% for the mean murine 1 log10-kill target for the cefepime/tazobactam combination. RESULTS: We found that to adjust for renal function, doses need to be reduced to 1 g q8h, 500 mg q8h and 500 mg q12h for patients with CLCR of 30-59, 15-29 and 8-14 mL/min (as well as patients with intermittent haemodialysis), respectively. In patients with high to augmented CLR (estimated CLCR 120-180 mL/min), a prolonged 4 h infusion of standard dose is required. CONCLUSIONS: The suggested dosing regimens will result in exposures of cefepime and tazobactam that would be adequate for infections caused by ESBL-producing pathogens with a cefepime/tazobactam MICs up to 16 mg/L.

'Under pressure': The role of therapeutic drug monitoring in the treatment of hypertension.

Antihypertensive drugs do not qualify as optimal candidates for therapeutic drug monitoring (TDM), given their obvious physiological effect, the absence of a clear relationship between drug concentrations and pharmacodynamic outcomes and their wide therapeutic range. However, since non-adherence is a major challenge in hypertension management, using drug concentrations can be of value to identify non-adherence as a first step towards better blood pressure control. In this article we discuss the key challenges associated with measuring and interpreting antihypertensive drug concentrations that are important when TDM is used to improve non-adherence. Additionally, we elaborate on the role of TDM in optimizing antihypertensive drug treatment besides addressing non-adherence by highlighting its value in specific patient groups with altered pharmacokinetic parameters such as female vs. male or elderly patients.

Therapeutic Drug Monitoring to Optimize Risperidone Treatment in Children with Autism Spectrum Disorder.

BACKGROUND: Risperidone is an atypical antipsychotic drug used to treat irritability and aggression in children and adolescents with autism spectrum disorder. In an earlier study, the sum trough concentration of risperidone and its metabolite (9-hydroxyrisperidone) was positively correlated with weight gain and effectiveness. The aim of this study was to determine the therapeutic window for risperidone sum trough concentrations that balances weight gain with treatment effectiveness in this population. In addition, the effect of therapeutic drug monitoring (TDM) on treatment optimization was simulated. METHODS: In a retrospective cohort (n = 24 children), the target window for risperidone leading to the least increase in body mass index z-scores while retaining effectiveness as measured by the irritability subscale of the Aberrant Behavior Checklist was determined using receiver operating curve analysis. This target range was used to simulate the effect of TDM using a population PK model implemented in the software platform InsightRX. Dosing advice was based on plasma trough concentrations and the dose administered at 12 weeks to simulate whether more children would be on target at 24 weeks after the start of treatment. RESULTS: A risperidone sum trough target range of 3.5-7.0 mcg/L would minimize increase in body mass index z-score and optimize effectiveness. Dosing advice using TDM and a population PK model would lead to a larger proportion of children achieving the target concentration range (62.5% versus 16.7%). CONCLUSIONS: TDM may be a useful tool for optimizing risperidone treatment in children and adolescents with autism spectrum disorder.

Experimental and computational framework for a dynamic protein atlas of human cell division.

Essential biological functions, such as mitosis, require tight coordination of hundreds of proteins in space and time. Localization, the timing of interactions and changes in cellular structure are all crucial to ensure the correct assembly, function and regulation of protein complexes1-4. Imaging of live cells can reveal protein distributions and dynamics but experimental and theoretical challenges have prevented the collection of quantitative data, which are necessary for the formulation of a model of mitosis that comprehensively integrates information and enables the analysis of the dynamic interactions between the molecular parts of the mitotic machinery within changing cellular boundaries. Here we generate a canonical model of the morphological changes during the mitotic progression of human cells on the basis of four-dimensional image data. We use this model to integrate dynamic three-dimensional concentration data of many fluorescently knocked-in mitotic proteins, imaged by fluorescence correlation spectroscopy-calibrated microscopy5. The approach taken here to generate a dynamic protein atlas of human cell division is generic; it can be applied to systematically map and mine dynamic protein localization networks that drive cell division in different cell types, and can be conceptually transferred to other cellular functions.

The Clearance of Midazolam and Metabolites during Continuous Renal Replacement Therapy in Critically Ill Patients with COVID-19.

INTRODUCTION: Midazolam-based continuous intravenous sedation in patients admitted to the intensive care unit (ICU) was a necessity during the COVID-19 pandemic. However, benzodiazepine-based sedation is associated with a high incidence of benzodiazepine-related delirium and additional days on mechanical ventilation. Due to the requirement of high midazolam doses in combination with the impaired renal clearance (CL) of the pharmacological active metabolite 1-OH-midazolam-glucuronide (10% compared to midazolam), ICU patients with COVID-19 and continuous renal replacement therapy (CRRT) were at risk of unintended prolonged sedation. Several CRRT-related factors may have influenced the delivered CL of midazolam and its metabolites. Therefore, the aim of the study was to identify and describe these CRRT-related factors. METHODS: Pre-filter blood samples and ultrafiltrate samples were collected simultaneously. Midazolam, 1-OH-midazolam, and 1-OH-midazolam-glucuronide plasma samples were analyzed using an UPLC-MS/MS method. The prescribed CRRT dose was corrected for downtime and filter integrity using the urea ratio (urea concentration in effluent/urea concentration plasma). CL of midazolam and its metabolites were calculated with the delivered CRRT dose (corrected for downtime and saturation coefficient [SD]). RESULTS: Three patients on continuous venovenous hemodialysis (CVVHD) and 2 patients on continuous venovenous hemodiafiltration (CVVHDF) were included. Midazolam, 1-OH-midazolam, and 1-OH-midazolam-glucuronide concentrations were 2,849 (0-6,700) µg/L, 153 (0-295) µg/L, and 27,297 (1,727-39,000) µg/L, respectively. The SD was 0.03 (0.02-0.03) for midazolam, 0.05 (0.05-0.06) for 1-OH-midazolam, and 0.33 (0.23-0.43) for 1-OH-midazolam-glucuronide. The delivered CRRT CL was 1.4 (0-1.7) mL/min for midazolam, 2.7 (0-3.5) mL/min for 1-OH-midazolam, and 15.7 (4.0-27.7) mL/min for 1-OH-midazolam-glucuronide. CONCLUSIONS: Midazolam and 1-OH-midazolam were not removed during CVVHD and CVVHDF. However, 1-OH-midazolam-glucuronide was removed reasonably, approximately up to 43%. CRRT modality, filter integrity, and downtime affect this removal. These data imply a personalized titration of midazolam in critically ill patients with renal failure and awareness for the additional sedative effects of its active metabolites.

In Vitro Elution of Gentamicin from CERAMENT® G Has an Antimicrobial Effect on Bacteria With Various Levels of Gentamicin Resistance Found in Fracture-related Infection.

BACKGROUND: Fracture-related infection is a serious complication after trauma. CERAMENT® G combines dead-space management with local release of gentamicin in a single-stage procedure. Bacterial resistance against antibiotics is increasing. The local effect of CERAMENT® G on bacteria resistant to systemically administered gentamicin is unknown. QUESTIONS/PURPOSES: (1) What is the in vitro elution pattern of gentamicin from CERAMENT® G using a full washout model? (2) What is the in vitro antimicrobial activity (zone of inhibition) of CERAMENT® G against bacterial isolates found in fracture-related infection with different susceptibility levels toward gentamicin? METHODS: Elution of gentamicin from CERAMENT® G was determined in vitro over a period of 2 months. Elution experiments were performed in fivefold, with gentamicin being sampled in threefold at 19 different timepoints within 2 months. Antimicrobial activity was determined using the four most-frequently cultured bacterial species found in fracture-related infection: Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Enterobacter cloacae . For each of the species, four different isolates with a different susceptibility to gentamicin were used. According to the European Committee on Antimicrobial Susceptibility Testing, the susceptibility of each isolate was classified into four different groups: fully susceptible (minimum inhibitory concentration 0.064 to 4 mg/L), minimally resistant (minimum inhibitory concentration 4 to 16 mg/L), moderately resistant (minimum inhibitory concentration 8 to 96 mg/L), and highly resistant (minimum inhibitory concentration 24 to 1024 mg/L), depending on each organism. The antimicrobial activity of CERAMENT® G was determined according to the European Committee on Antimicrobial Susceptibility Testing disk protocol. The experiment was performed in fivefold for each isolate. The zone of inhibition was compared between each bacterial isolate and within each of the four separate species. Nonlinear regression statistics were calculated between the zone of interest and logarithmic minimum inhibitory concentration for each bacterial species. RESULTS: After 24 hours, 95% of all available gentamicin was eluted, and gentamicin was still detectable after 2 months. CERAMENT® G showed antimicrobial activity against all bacterial species; only S taphylococcus aureus (with a minimum inhibitory concentration > 1024 mg/L) was not susceptible. The zone of interest of the different bacterial isolates was correlated with the logarithmic minimum inhibitory concentration. CONCLUSION: CERAMENT® G offers a bone substitute capable of releasing high levels of gentamicin within a short period of time. This study shows that CERAMENT® G has antimicrobial activity against bacterial isolates that are resistant to gentamicin when systemically administered. This finding raises the question of whether European Committee on Antimicrobial Susceptibility Testing cutoff points for systemic application are useful for the use of local CERAMENT® G. Standardized experiments to determine local antibiotic antimicrobial activity in fracture-related infection treatment are needed to form guidelines for the use of local antibiotics and ultimately improve fracture-related infection treatment. CLINICAL RELEVANCE: Local concentrations of gentamicin with CERAMENT® G are much higher than when systemically administered. It seems effective against certain bacterial strains that are not affected by systemically reachable concentrations of gentamicin. CERAMENT® G might still be effective when bacteria that are resistant to systemically administered concentrations of gentamicin are occulated from patients with fracture-related infection.

Comparison of antipsychotic drug use in children and adolescents in the Netherlands before and during the COVID-19 pandemic.

This study aims to describe the patterns and trends in antipsychotic prescription among Dutch youth before and during the corona virus disease 2019 (COVID-19) pandemic (between 2017 and 2022). The study specifically aims to determine whether there has been an increase or decrease in antipsychotic prescription among this population, and whether there are any differences in prescription patterns among different age and sex groups. The study utilized the IADB database, which is a pharmacy prescription database containing dispensing data from approximately 120 community pharmacies in the Netherlands, to analyze the monthly prevalence and incidence rates of antipsychotic prescription among Dutch youth before and during the pandemic. The study also examined the prescribing patterns of the five most commonly used antipsychotics and conducted an autoregressive integrated moving average (ARIMA) analysis using data prior to the pandemic, to predict the expected prevalence rate during the pandemic. The prescription rate of antipsychotics for Dutch youth was slightly affected by the pandemic, with a monthly prevalence of 4.56 [4.50-4.62] per 1000 youths before COVID-19 pandemic and 4.64 [4.59-4.69] during the pandemic. A significant increase in prevalence was observed among adolescent girls aged 13-19 years. The monthly incidence rate remained stable overall, but rose for adolescent girls aged 13-19 years. Aripiprazole, and Quetiapine had higher monthly prevalence rates during the pandemic, while Risperidone and Pipamperon had lower rates. Similarly, the monthly incidence rates of Aripiprazole and Olanzapine went up, while Risperidone went down. Furthermore, the results from the ARIMA analysis revealed that despite the pandemic, the monthly prevalence rate of antipsychotic prescription was within expectation. The findings of this study suggest that there has been a moderate increase in antipsychotic prescription among Dutch youth during the COVID-19 pandemic, particularly in adolescent females aged 13-19 years. However, the study also suggests that factors beyond the pandemic may be contributing to the rise in antipsychotic prescription in Dutch youth.

Oral and Intravenous Amoxicillin Dosing Recommendations in Neonates: A Pooled Population Pharmacokinetic Study.

BACKGROUND: There is a lack of evidence on oral amoxicillin pharmacokinetics and exposure in neonates with possible serious bacterial infection (pSBI). We aimed to describe amoxicillin disposition following oral and intravenous administration and to provide dosing recommendations for preterm and term neonates treated for pSBI. METHODS: In this pooled-population pharmacokinetic study, 3 datasets were combined for nonlinear mixed-effects modeling. In order to evaluate amoxicillin exposure following oral and intravenous administration, pharmacokinetic profiles for different dosing regimens were simulated with the developed population pharmacokinetic model. A target of 50% time of the free fraction above the minimal inhibitory concentration (MIC) with an MICECOFF of 8 mg/L (to cover gram-negative bacteria such as Escherichia coli) was used. RESULTS: The cohort consisted of 261 (79 oral, 182 intravenous) neonates with a median (range) gestational age of 35.8 weeks (range, 24.9-42.4) and bodyweight of 2.6 kg (range, 0.5-5). A 1-compartment model with first-order absorption best described amoxicillin pharmacokinetics. Clearance (L/h/kg) in neonates born after 30 weeks' gestation increased with increasing postnatal age (PNA day 10, 1.25-fold; PNA day 20, 1.43-fold vs PNA day 3). Oral bioavailability was 87%. We found that a twice-daily regimen of 50 mg/kg/day is superior to a 3- or 4-times daily schedule in the first week of life for both oral and intravenous administration. CONCLUSIONS: This pooled population pharmacokinetic description of intravenous and oral amoxicillin in neonates provides age-specific dosing recommendations. We conclude that neonates treated with oral amoxicillin in the first weeks of life reach adequate amoxicillin levels following a twice-daily dosing regimen. Oral amoxicillin therapy could therefore be an adequate, cost-effective, and more patient-friendly alternative for neonates worldwide.

Chemogenetic Control of Nanobodies.

We introduce an engineered nanobody whose affinity to green fluorescent protein (GFP) can be switched on and off with small molecules. By controlling the cellular localization of GFP fusion proteins, the engineered nanobody allows interrogation of their roles in basic biological processes, an approach that should be applicable to numerous previously described GFP fusions. We also outline how the binding affinities of other nanobodies can be controlled by small molecules.

Plasma protein binding of ceftriaxone in critically ill patients: can we predict unbound fractions?

BACKGROUND: Standard antibiotic dosing is not suitable for critically ill patients, due to altered pharmacokinetics (PK) in these patients. Knowledge of protein binding is important for optimizing antibiotic exposure because only the unbound fraction is pharmacologically active. If unbound fractions can be predicted, minimal sampling techniques and less costly methods can be routinely used. METHODS: Data from the DOLPHIN trial, a prospective randomized clinical trial that included critically ill patients, were used. Total and unbound ceftriaxone concentrations were determined using a validated UPLC-MS/MS method. A non-linear saturable binding model was made using 75% of the trough concentrations and validated on the remaining data. Our model and previously published models were tested for their performance for subtherapeutic (<1 mg/L) and high (>10 mg/L) unbound concentrations. RESULTS: In total, 113 patients were sampled [Acute Physiology And Chronic Health Evaluation version 4 (APACHE IV) score 71 (IQR 55-87), albumin 28 g/L (IQR 24-32)]. This resulted in 439 samples (trough = 224, peak = 215). Unbound fractions were significantly different between samples taken at trough and peak times [10.9% (IQR 7.9-16.4) versus 19.7% (IQR 12.9-26.6), P < 0.0001], which was not explained by concentration differences. Our model and most literature models showed good sensitivity and low specificity to determine high and subtherapeutic ceftriaxone trough concentrations using only the total ceftriaxone and albumin concentrations. CONCLUSIONS: Ceftriaxone protein binding is not concentration related in critically ill patients. Existing models show good ability to predict high concentrations, but low specificity in predicting subtherapeutic concentrations.

Dose optimization of cefotaxime as pre-emptive treatment in critically ill adult patients: A population pharmacokinetic study.

AIMS: To describe the pharmacokinetics (PK) of cefotaxime as pre-emptive treatment in critically ill adult patients, including covariates and to determine the probability of target attainment (PTA) of different dosage regimens for Enterobacterales and Staphylococcus aureus. METHODS: Five samples were drawn during 1 dosage interval in critically ill patients treated with cefotaxime 1 g q6h or q4h. PK parameters were estimated using NONMEM (v7.4.2). The percentage of patients reaching 100% fT>MICECOFF was used to compare different dosage regimens for Enterobacterales and S. aureus. RESULTS: This study included 92 patients (437 samples). The best structural model was a 2-compartment model with a combined error, interindividual variability on clearance, central volume and intercompartmental clearance. Correlations between interindividual variability were included. Clearance increased with higher estimated glomerular filtration rate (eGFR; creatinine clearance) and albumin concentration. For Enterobacterales, 1 g q8h reached 95% PTA and continuous infusion (CI) of 4 g 24 h-1 100% PTA at the highest eGFR and albumin concentration. For S. aureus the predefined target of 95% PTA was not reached with higher eGFR and/or albumin concentrations. CI of 6 g 24 h-1 for S. aureus resulted in a minimum of 99% PTA. CONCLUSION: Cefotaxime PK in critically ill patients was best described by a 2-compartment model with eGFR and albumin concentration as covariates influencing clearance. For Enterobacterales 1 g q8h or CI of 4 g 24 h-1 was adequate for all combinations of eGFR and albumin concentration. For S. aureus CI of 6 g 24 h-1 would be preferred if eGFR and albumin concentration exceed 80 mL min-1 and 40 g L-1 respectively.

Towards precision dosing of aripiprazole in children and adolescents with autism spectrum disorder: Linking blood levels to weight gain and effectiveness.

AIMS: Aripiprazole is one of the most commonly prescribed antipsychotic drugs to children and adolescents worldwide, but it is associated with serious side-effects, including weight gain. This study assessed the population pharmacokinetics of aripiprazole and its active metabolite and investigated the relationship between pharmacokinetic parameters and body mass index (BMI) in children and adolescents with autism spectrum disorder (ASD) and behavioural problems. Secondary outcomes were metabolic, endocrine, extrapyramidal and cardiac side-effects and drug effectiveness. METHODS: Twenty-four children and adolescents (15 males, 9 females) aged 6-18 years were included in a 24-week prospective observational trial. Drug plasma concentrations, side-effects and drug effectiveness were measured at several time points during follow-up. Relevant pharmacokinetic covariates, including CYP2D6, CYP3A4, CYP3A5 and P-glycoprotein (ABCB1) genotypes, were determined. Nonlinear mixed-effects modelling (NONMEM®) was used for a population pharmacokinetic analysis with 92 aripiprazole and 91 dehydro-aripiprazole concentrations. Subsequently, model-based trough concentrations, maximum concentrations and 24-h area under the curves (AUCs) were analysed to predict outcomes using generalized and linear mixed-effects models. RESULTS: For both aripiprazole and dehydro-aripiprazole, one-compartment models best described the measured concentrations, with albumin and BMI as significant covariates. Of all the pharmacokinetic parameters, higher sum (aripiprazole plus dehydro-aripiprazole) trough concentrations best predicted higher BMI z-scores (P < .001) and higher Hb1Ac levels (P = .03) during follow-up. No significant association was found between sum concentrations and effectiveness. CONCLUSIONS: Our results indicate a threshold with regard to safety, which suggests that therapeutic drug monitoring of aripiprazole could potentially increase safety in children and adolescents with ASD and behavioural problems.

Stability of 10 Beta-Lactam Antibiotics in Human Plasma at Different Storage Conditions.

BACKGROUND: Recently, several studies have assessed the effects of therapeutic drug monitoring of frequently prescribed beta-lactam antibiotics, for which they were quantified in human plasma samples. Beta-lactams are considered unstable, leading to extra challenges in quantification. Therefore, to ensure sample stability and minimize sample degradation before analysis, stability studies are crucial. This study investigated the stability of 10 frequently used beta-lactam antibiotics in human plasma at relevant storage conditions for clinical use. METHODS: Amoxicillin, benzylpenicillin, cefotaxime, ceftazidime, ceftriaxone, cefuroxime, flucloxacillin, imipenem, meropenem, and piperacillin were analyzed using ultraperformance convergence chromatography tandem mass spectrometry and liquid chromatography tandem mass spectrometry. Their short-term and long-term stabilities were investigated by measuring quality control samples at low and high concentrations against freshly prepared calibration standards. Measured concentrations at each time point were compared with the concentrations at T = 0. Antibiotics were considered stable if recovery results were between 85% and 115%. RESULTS: Short-term stability results indicated ceftriaxone, cefuroxime, and meropenem to be stable up to 24 hours at room temperature. All evaluated antibiotics, except imipenem, were stable on ice in a cool box for 24 hours. Amoxicillin, benzylpenicillin, and piperacillin were stable for 24 hours at 4-6°C. Cefotaxime, ceftazidime, cefuroxime, and meropenem were stable at 4-6°C up to 72 hours. Ceftriaxone and flucloxacillin were stable for 1 week at 4-6°C. Long-term stability results showed that all antibiotics were stable up to 1 year at -80°C, except imipenem and piperacillin, which were stable for 6 months at -80°C. CONCLUSIONS: Plasma samples for amoxicillin, benzylpenicillin, cefotaxime, ceftazidime, flucloxacillin, and piperacillin may be stored for a maximum of 24 hours in a cool box. Refrigeration is suitable for plasma samples of amoxicillin, benzylpenicillin, meropenem, and piperacillin for up to 24 hours and cefotaxime, ceftriaxone, ceftazidime and cefuroxime for 72 hours. Plasma samples for imipenem should be frozen directly at -80°C. For long-term storage, plasma samples can be stored at -80°C for a maximum of 6 months for imipenem and piperacillin and 12 months for all other evaluated antibiotics.

Population plasma and urine pharmacokinetics and the probability of target attainment of fosfomycin in healthy male volunteers.

PURPOSE: A population pharmacokinetic model of fosfomycin was developed in healthy volunteers after intravenous administration, and different dosing regimens were evaluated in terms of the probability of target attainment for Escherichia coli using both plasma and urinary pharmacokinetic/pharmacodynamic targets. METHODS: Eight healthy men received fosfomycin as both intermittent 8 g q8h and continuous infusion 1 g/h with a loading dose of 8 g in a crossover study design. Dense sampling was conducted during both regimens. Population pharmacokinetic modelling was performed using NONMEM. Monte Carlo simulations were conducted to evaluate the Probability of Target Attainment (PTA) of different dosing regimens using bactericidal (AUC24h/MIC of 83 and 75%T>MIC) and bacteriostatic (AUC24h/MIC of 25) plasma targets and bacteriostatic (AUC24h/MIC of 3994) urine target. RESULTS: A total of 176 plasma and 86 urine samples were available for PK analysis. A two-compartment model with a urine compartment best described the data. Glomerular filtration rate (GFR) showed a significant correlation with renal clearance and was implemented in the final model. Simulation results show that the dose of 4 g q8h reached 100% of PTA using bactericidal and bacteriostatic targets for MIC up to 16 mg/L. CONCLUSION: For the clinical breakpoint of 32 mg/L, the standard dosing regimen (4 g q8h) might not be sufficient to reach the bactericidal target. Higher dosing of 8 g q8h as an intermittent infusion or 0.75 g/h as a continuous infusion might be required. Continuous infusion resulted in better attainment of the %T>MIC target than intermittent infusion.

Pursuing the Real Vancomycin Clearance during Continuous Renal Replacement Therapy in Intensive Care Unit Patients: Is There Adequate Target Attainment?

INTRODUCTION: Vancomycin is used in intensive care unit (ICU) patients for the treatment of infections caused by gram-positive bacteria. The vancomycin pharmacokinetic/pharmacodynamic index is a ratio of the area under the concentration to the minimum inhibitory concentration ≥400-600 h*mg/L. This target can generally be achieved by a plasma concentration of 20-25 mg/L. Together with the pathophysiological alterations and pharmacokinetic variability associated with critical illness, the use of continuous renal replacement therapy (CRRT) may complicate the attainment of adequate vancomycin concentrations. The primary objective was the prevalence of attainment of vancomycin concentrations 20-25 mg/L after 24 h in adult ICU patients receiving CRRT. Secondary outcomes were to evaluate target attainment at days 2 and 3 and to calculate vancomycin clearance (CL) by CRRT and residual diuresis. METHODS: We performed a prospective observational study in adult ICU patients on CRRT, which received at least 24 h continuous infusion of vancomycin. Between May 2020 and February 2021, daily vancomycin residual blood gas and dialysate samples were collected from 20 patients, every 6 h and if possible vancomycin urine samples. Vancomycin was analysed with an immunoassay method. The CL by CRRT was calculated by a different approach correcting for the downtime and providing insight into the degree of filter patency. RESULTS: The proportion of patients with vancomycin concentrations <20 mg/L was 50% 24 h after starting vancomycin (n = 10). No differences were observed in patient characteristics. The target vancomycin concentration 20-25 mg/L was only achieved in 30% of the patients. On days 2 and 3, despite the use of TDM and albeit in lower percentages, sub- and supratherapeutic levels were still observed. Taking downtime and filter patency into account resulted in lower vancomycin CL. CONCLUSIONS: 50% of the studied ICU patients on CRRT showed subtherapeutic vancomycin concentrations 24 h after starting therapy. The results reveal that optimization of vancomycin dosage during CRRT therapy is needed.

Alternative dosing strategies for immune checkpoint inhibitors to improve cost-effectiveness: a special focus on nivolumab and pembrolizumab.

Immune checkpoint inhibitors have revolutionised cancer treatment by offering durable responses to many patients with solid and haematological cancers. The high prices and increasing use of immune checkpoint inhibitors put considerable strain on health-care budgets globally. This financial strain could jeopardise patients' access to these anti-cancer therapies. However, substantial evidence suggests that immune checkpoint inhibitors are being administered at doses that exceed the minimum dose required for maximum anti-tumour efficacy. Therefore, investigating and implementing the most cost-effective dosing strategies for immune checkpoint inhibitors are urgently necessary. This Personal View provides an overview of existing data on immune checkpoint inhibitor pharmacology and (novel) dosing strategies for anti-PD-1 therapy with nivolumab and pembrolizumab, with a special focus on cost-effectiveness and saving potential. Furthermore, specific recommendations to guide health-care professionals are provided, through the process of prescribing, rounding, preparing, and administering nivolumab and pembrolizumab in the most practical and cost-effective way possible.