Population pharmacokinetics of tobramycin administered thrice daily and once daily in children and adults with cystic fibrosis

Evaluation of Target Attainment for Tobramycin in Children and Adults with Cystic Fibrosis

Introduction: Patients with cystic fibrosis (CF) commonly experience pulmonary exacerbations, and it is recommended by the TOPIC study to treat this with tobramycin at a dose of 10 mg/kg once daily. The aim of this study was to evaluate the target attainment of the current dosing regimen. Methods: A single-center retrospective cohort study of child and adult patients with CF who received tobramycin between 2019 and 2022 was conducted. Descriptive statistics and linear mixed models were used to assess target attainment for tobramycin. Results: In total, 25 patients (53 courses), of which 10 were children (12 courses) and 15 were adults (41 courses), were included. Those 25 patients all received 10 mg/kg/day. The tobramycin peak concentrations were supratherapeutic in 82.9% and therapeutic in 100.0% of adults and children, respectively. The trough concentrations were outside the target range in 0% and 5.1% of children and adults, respectively. We found lower tobramycin concentrations with the same dose in children compared to adults. Conclusions: This study illustrates the need to validate dosing advice in a real-world setting, as supratherapeutic concentrations of tobramycin were prevalent in adults with CF.

Novel grape seed extract nanoparticles attenuate amikacin-induced nephrotoxicity in rats

Amikacin (AMK), an antibiotic, is prescribed for treating various bacterial diseases like urinary tract infections, encephalitis, asthma and joint infections. The most significant side effects, which affect 1 to 10% of consumers, are kidney injury and ototoxicity. Several studies discussed the role of grape seed extract (GSE) in renoprotection against AMK. The current study aimed to extract Muscat of Alexandria grape seeds followed by its characterization to determine its bioactive components and elements. GSE nanoparticles was prepared and tested, in vitro, to determine its safety for the in vivo experiment. Experimental groups were control group I, AMK group II, GSE (50 mg/kg)-AMK group III, GSE (100 mg/kg)-AMK group IV, GSE NPs (25 mg/kg)-AMK group V and GSE NPs (50 mg/kg)-AMK group VI. Groups 2-6 received 100 mg/kg/day of AMK by intramuscular injection for two weeks for the induction of experimental nephrotoxicity. Groups 3-6 received daily doses of GSE or GSE NPs by oral gavage, concurrently, with AMK for two weeks. GSE was rich in polyphenol compounds like proanthocyanidins, phenolic acids like gallic and egallic acids, catechine and epicatechine. GSE NPs have a smooth surface and a size that ranged from 40 to 70 nm; and have an anti-oxidant, anti-inflammatory, anti-cytotoxic and anti-microbial in vitro effects. It reduced oxidative stress and inflammation that followed AMK administration; and attenuated the AMK-induced nephrotoxicity. GSE NPs were safe to be used in vivo as a renoprotective agent against AMK; where, it reduced the oxidative stress and inflammation.

Exploration of the relationship between cumulative exposure to tobramycin and ototoxicity in patients with cystic fibrosis

BACKGROUND

Aminoglycosides (AGs), such as tobramycin, are essential antibiotics in the management of pulmonary infections in patients with cystic fibrosis (CF). They induce ototoxicity without the relationship being clearly described in the literature. Our aim is to propose a mathematical and statistical model describing the relationship between the estimated cumulative exposure (Area Under the Curve, AUC) to tobramycin and ototoxicity with audiogram interpretation in young patients with CF.

METHODS

Cumulative AUCs were estimated for each course of tobramycin, for the 106 individuals with CF (between 4 and 22 years of age) enrolled in this retrospective study (35 who had received IV tobramycin, 71 controls). Mean hearing loss was calculated for each audiogram and a statistical model was developed to predict hearing loss.

RESULTS

The model confirms a significant relationship between cumulative tobramycin exposure and changes in hearing acuity: Meanhearingloss=2.7+(3×10-5)×AUC_tobramycin+individual_susceptibility However, the ototoxic effect is not clinically perceptible (mean hearing loss: 3.8 dB). The impact of AUC on hearing loss is minor in these subjects who received a limited number of courses of tobramycin (median: 5 courses).

CONCLUSION

A significant relationship between cumulative exposure to tobramycin and ototoxicity was demonstrated. Individual treatment susceptibility should not be overlooked. As ototoxicity is not clinically perceptible in the study subjects, hearing tests should be continued during adulthood to provide individualized medical guidance and to obtain a lifetime analysis of the relationship between exposure and hearing loss.

New Recommendations of a Height-Based Dosing Regimen of Tobramycin for Cystic Fibrosis in Adults: A Population Pharmacokinetic Analysis

BACKGROUND

Acute pulmonary exacerbations (APEs) in patients with adult cystic fibrosis (CF) are treated with a beta-lactam and an aminoglycoside for activity against Pseudomonas aeruginosa (PA). Emerging drug resistance and changing pharmacokinetic profile in an aging population involve a reevaluation of tobramycin dosing recommendations. The objective of this study was to develop a population pharmacokinetic model and establish optimal dosing recommendations for tobramycin using Monte Carlo simulations.

METHODS

This retrospective clinical study and data collection were performed at the CF center of the McGill University Health Center (MUHC), Canada. Model development and simulations were performed using a nonlinear mixed-effect modeling approach (NONMEM, version 7.4.2). The ratios of maximal concentration (C max ) to the minimal inhibitory concentration (MIC) (C max /MIC ≥8 and ≥10) and area under the curve (AUC) to the MIC (AUC/MIC ≥70 and ≥100) were evaluated.

RESULTS

Adult patients with CF (n = 51) treated with tobramycin were included in the study. Plasma concentrations of tobramycin were obtained for 699 samples from the MUHC database. The two-compartmental model best described the pharmacokinetics of tobramycin. The association of patient height with the central volume of distribution significantly improved this model. Height, rather than weight, induced the best reduction in objective function. According to simulations, doses between 3.4 mg/cm and 4.4 mg/cm were necessary to achieve C max /MIC values of ≥8 and ≥10, respectively. However, higher doses were required to achieve the AUC/MIC targets.

CONCLUSIONS

This study demonstrated that height of the patients seems to be more suitable than their weight for dosing adjustments in adult patients with CF. According to this model, initial doses of tobramycin between 3.4 and 4.4 mg/cm should be recommended for patients with a median height of 164 cm and weight of 55 kg to achieve the target plasma concentrations.

A Pharmacokinetic Analysis of Tobramycin in Patients Less than Five Years of Age with Cystic Fibrosis: Assessment of Target Attainment with Extended-Interval Dosing through Simulation

Extended interval dosing of tobramycin is recommended for treatment of pulmonary exacerbations in adults and older children with cystic fibrosis (CF), but data are limited in patients less than 5 years of age. We performed a retrospective population pharmacokinetic (PK) analysis of hospitalized children with CF <5 years of age prescribed intravenous tobramycin for a pulmonary exacerbation from March 2011 to September 2018 at our hospital. Children with normal renal function who had ≥1 tobramycin concentration available were included. Nonlinear mixed effects population PK modeling was performed using NONMEM using data from the first 48 h of tobramycin treatment. Monte Carlo simulations were implemented to determine the fraction of simulated patients that met published therapeutic targets with regimens of 10-15 mg/kg/day once-daily dosing. Fifty-eight patients received 111 tobramycin courses (range 1-9/patient). A two-compartment model best described the data. Age, glomerular filtration rate, and vancomycin coadministration were significant covariates on tobramycin clearance. The typical values of clearance and central volume of distribution were 0.252 L/hr/kg^0.75 and 0.308 L/kg, respectively. No once-daily regimens achieved all pre-specified targets simultaneously in >75% of simulated subjects. A dosage of 13 mg/kg/dose best met the predefined targets of C_max >25 mg/L and AUC₂₄ of 80-120 mg·h/L. Based on our population PK analysis and simulations, once-daily dosing of tobramycin would not achieve all therapeutic goals in young patients with CF. However, extended-interval dosing regimens may attain therapeutic targets in the majority of young patients.

Aminoglycoside dosing and monitoring for Pseudomonas aeruginosa during acute pulmonary exacerbations in cystic fibrosis

Aminoglycosides are commonly used for the treatment of Pseudomonas aeruginosa (PsA) in the setting of acute pulmonary exacerbations (PEx) in pediatric patients with cystic fibrosis (CF). There are controversies and practice differences between institutions related to aminoglycoside dosing and monitoring strategies. The purpose of this review article is to summarize the currently available literature and identify gaps in the literature related to pharmacokinetic parameter goals, aminoglycoside dosing strategies, and methods for monitoring serum aminoglycoside concentrations for treatment of PsA in CF PEx, and throughout will discuss anticipated changes with the increasing availability of highly effective CF transmembrane conductance regulator modulators. This review focuses on tobramycin, as it is the most commonly used aminoglycoside in CF PEx, and will briefly discuss special circumstances surrounding use of amikacin and gentamicin.

Consideration of height-based tobramycin dosing regimens for the treatment of adult cystic fibrosis pulmonary exacerbations

AIMS

Some population pharmacokinetic models have been developed using height to explain some of the interindividual variability in tobramycin pharmacokinetics in cystic fibrosis patients. However, their predictive performance when extrapolated to other clinical centres is unclear. Therefore, the aim of this study was to externally evaluate the predictability of tobramycin population pharmacokinetic models with an independent dataset and perform simulations using previously recommended height-based dosing regimens.

METHODS

A literature search was conducted through the PubMed database to identify relevant population pharmacokinetic models. Tobramycin plasma concentration data from April 2014 to November 2019 were retrospectively collected from the Institut universitaire de cardiologie et de pneumologie de Québec, Canada. External evaluations were performed using NONMEM® v7.5 and RStudio® v1.3.1073. Monte Carlo simulations were performed to evaluate the probability of target attainment of C_max /MIC ratios for several dosing regimens.

RESULTS

The validation dataset included 27 patients and 143 concentration samples. Three models were evaluated. Only the ones by Crass et al. and Alghanem et al. performed satisfactorily in terms of prediction-based diagnostics with MDPE values of -3.4% and 29.3% and MDAPE values of 19.0 and 29.5%, respectively. In simulation-based evaluations, both pcVPC and NPDE showed no evidence of model misspecification. Our simulations suggest that patients treated with a once-daily dose of 3.4 mg/cm should produce peak and trough levels consistent with current guidelines.

CONCLUSION

Our results show that the models by Crass et al. and Alghanem et al. are appropriate for simulation-based applications to aid individualized dosing in our population and that height-based dosing regimens could be considered in cystic fibrosis patients.

Does Circadian Rhythm Affect the Pharmacokinetics of Once-Daily Tobramycin in Adults With Cystic Fibrosis?

BACKGROUND

In the era of multiple daily dosing of systemic aminoglycosides, a circadian rhythm in the clearance of these vital antibiotics has been demonstrated in animals and healthy volunteers. Over the past decade, once-daily dosing regimens have been proved to be less nephrotoxic and were therefore adopted worldwide for most indications requiring treatment with an aminoglycoside. In this study, the effect of the time of administration on the pharmacokinetics of once-daily tobramycin in adults with cystic fibrosis (CF) experiencing a pulmonary exacerbation was investigated.

METHODS

In this open randomized study, patients with CF received intravenous tobramycin at 8:00 or 22:00 hours. Pharmacokinetic and kidney function parameters were compared between the 2 groups.

RESULTS

Twenty-five patients were included. The mean weight-corrected clearances of tobramycin were 1.46 versus 1.43 mL/h*kg (P = 0.50) and mean volumes of distribution were 0.25 versus 0.27 L/kg (P = 0.54) for the 8:00 and 22:00 groups, respectively. In addition, no significant differences were detected in changes in estimated clearances of creatinine or tobramycin on day 1 and day 8 in the 8:00 or 22:00 group, indicating that there was no decline in clearance over time. At day 8 of therapy, the increase in serum blood urea nitrogen in the 22:00 group was significantly higher than that in the 8:00 group (1.8 versus 0.2 mmol/L, P = 0.015).

CONCLUSIONS

The time of administration (8:00 versus 22:00) did not affect tobramycin pharmacokinetics in the adult CF population studied. The increase in serum blood urea nitrogen in the 22:00 group requires further investigation.

Population pharmacokinetic modeling and dosing simulations of tobramycin in pediatric patients with cystic fibrosis

Initial dosing and dose adjustment of intravenous tobramycin in cystic fibrosis children is challenging. The objectives of this study were to develop nonparametric population pharmacokinetic (PK) models of tobramycin in children with CF to be used for dosage design and model-guided therapeutic drug monitoring. We performed a retrospective analysis of tobramycin PK data in our CF children center. The Pmetrics package was used for nonparametric population PK analysis and dosing simulations. Both the maximal concentration over the MIC (Cmax/MIC) and daily area under the concentration-time curve to the MIC (AUC₂₄/MIC) ratios were considered as efficacy target. Trough concentration (Cmin) was considered as the safety target. A total of 2884 tobramycin concentrations collected in 195 patients over 9 years were analyzed. A two-compartment model including total body weight, body surface area and creatinine clearance as covariates best described the data. A simpler model was also derived for implementation into the BestDose software to perform Bayesian dose adjustment. Both models were externally validated. PK/PD simulations with the final model suggest that an initial dose of tobramycin of 15 to 17.5 mg/kg/day was necessary to achieve Cmax/MIC ≥ 10 values for MIC values up to 2 mg/L in most patients. The AUC₂₄/MIC target was associated with larger dosage requirements and higher Cmin. A daily dose of 12.5 mg/kg would optimize both efficacy and safety target attainment. We recommend to perform tobramycin TDM, model-based dose adjustment, and MIC determination to individualize intravenous tobramycin therapy in children with CF.

Pharmacokinetic and Pharmacodynamic Optimization of Antibiotic Therapy in Cystic Fibrosis Patients: Current Evidences, Gaps in Knowledge and Future Directions

Antibiotic therapy is one of the main treatments for cystic fibrosis (CF). It aims to eradicate bacteria during early infection, calms down the inflammatory process, and leads to symptom resolution of pulmonary exacerbations. CF can modify both the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of antibiotics, therefore specific PK/PD endpoints should be determined in the context of CF. Currently available data suggest that optimal PK/PD targets cannot be attained in sputum with intravenous aminoglycosides. Continuous infusion appears preferable for β-lactam antibiotics, but optimal concentrations in sputum are unlikely to be reached, with some possible exceptions such as meropenem and ceftolozane. Usual doses are likely suboptimal for fluoroquinolones and linezolid, whereas daily doses of 45-60 mg/kg and 200 mg could be convenient for vancomycin and doxycycline, respectively. Weekly azithromycin doses of 22-30 mg/kg could also be appropriate for its anti-inflammatory effect. The difficulty with achieving optimal concentrations supports the use of combined treatments and the inhaled administration route, as very high local concentrations, concomitantly with low systemic exposure, can be obtained with the inhaled route for aminoglycosides, colistin, and fluoroquinolones, thus minimizing the risk of toxicity.

Antibiotics in Adult Cystic Fibrosis Patients: A Review of Population Pharmacokinetic Analyses

BACKGROUND

Lower respiratory tract infections are common in adult patients with cystic fibrosis (CF) and are frequently caused by Pseudomonas aeruginosa, resulting in chronic lung inflammation and fibrosis. The progression of multidrug-resistant strains of P. aeruginosa and alterations in the pharmacokinetics of many antibiotics in CF make optimal antimicrobial therapy a challenge, as reflected by high between- and inter-individual variability (IIV).

OBJECTIVES

This review provides a synthesis of population pharmacokinetic models for various antibiotics prescribed in adult CF patients, and aims at identifying the most reported structural models, covariates and sources of variability influencing the dose-concentration relationship.

METHODS

A literature search was conducted using the PubMed database, from inception to August 2020, and articles were retained if they met the inclusion/exclusion criteria.

RESULTS

A total of 19 articles were included in this review. One-, two- and three-compartment models were reported to best describe the pharmacokinetics of various antibiotics. The most common covariates were lean body mass and creatinine clearance. After covariate inclusion, the IIV (range) in total body clearance was 27.2% (10.40-59.7%) and 25.9% (18.0-33.9%) for β-lactams and aminoglycosides, respectively. IIV in total body clearance was estimated at 36.3% for linezolid and 22.4% for telavancin. The IIV (range) in volume of distribution was 29.4% (8.8-45.9%) and 15.2 (11.6-18.0%) for β-lactams and aminoglycosides, respectively, and 26.9% for telavancin. The median (range) of residual variability for all studies, using a combined (proportional and additive) model, was 12.7% (0.384-30.80%) and 0.126 mg/L (0.007-1.88 mg/L), respectively.

CONCLUSION

This is the first review that highlights key aspects of different population pharmacokinetic models of antibiotics prescribed in adult CF patients, effectively proposing relevant information for clinicians and researchers to optimize antibiotic therapy in CF.

The pharmacokinetics of antibiotics in cystic fibrosis

INTRODUCTION

Dosing of antibiotics in people with cystic fibrosis (CF) is challenging, due to altered pharmacokinetics, difficulty of lung tissue penetration, and increasing presence of antimicrobial resistance.

AREAS COVERED

The purpose of this work is to critically review original data as well as previous reviews and guidelines on pharmacokinetics of systemic and inhaled antibiotics in CF, with the aim to propose strategies for optimization of antibacterial therapy in both children and adults with CF.

EXPERT OPINION

For systemic antibiotics, absorption is comparable in CF patients and non-CF controls. The volume of distribution (Vd) of most antibiotics is similar between people with CF with normal body composition and healthy individuals. However, there are a few exceptions, like cefotiam and tobramycin. Many antibiotic class-dependent changes in drug metabolism and excretion are reported, with an increased total body clearance for ß-lactam antibiotics, aminoglycosides, fluoroquinolones, and trimethoprim. We, therefore, recommend following class-specific guidelines for CF, mostly resulting in higher dosages per kg bodyweight in CF compared to non-CF controls. Higher local antibiotic concentrations in the airways can be obtained by inhalation therapy, with which eradication of bacteria may be achieved while minimizing systemic exposure and risk of toxicity.

Area under the curve achievement of once daily tobramycin in children with cystic fibrosis during clinical care

BACKGROUND

The area under the concentration-time curve over 24 hours (AUC₂₄ ) is frequently utilized to monitor tobramycin exposure in children with cystic fibrosis (CF). An understanding of exposure target achievement during clinical implementation of an AUC₂₄ based approach in children is limited.

METHODS

A retrospective chart review was performed in children with CF treated with once daily tobramycin and drug concentration monitoring at a pediatric CF center. During clinical care AUC₂₄ was estimated using a traditional log-linear regression approach (LLR). AUC₂₄ was also estimated retrospectively using a pharmacokinetic model-based Bayesian forecasting approach (BF). AUC₂₄ achievement after both approaches were compared.

RESULTS

In 77 treatment courses (mean age, 12.7 ± 5.0 years), a target AUC₂₄ 100 to 125 mg h/L was achieved after starting dose in 21 (27%) and after initial dose adjustment in 35 (45%). In the first 7 days of treatment, 24 (32%) required ≥3 dose adjustments, and the mean number of drug concentrations measured was 7.1 ± 3.2. Examination of a BF approach demonstrated adequate prediction of measured tobramycin concentrations (median bias -2.1% [95% CI -3.1 to -1.4]; median precision 7.6% [95% CI, 7.1%-8.2%]). AUC₂₄ estimates utilizing the BF approach were higher than the LLR approach with a mean difference of 6.4 mg h/L (95% CI, 4.8 to 8.0 mg h/L).

CONCLUSIONS

Achievement of a narrow AUC₂₄ target is challenging during clinical care, and dose individualization is needed in most children with CF. Implementing a BF approach for estimating AUC₂₄ in children with CF is supported.

Bacterial persisters in long-term infection: Emergence and fitness in a complex host environment

Despite intensive antibiotic treatment, Pseudomonas aeruginosa often persists in the airways of cystic fibrosis (CF) patients for decades, and can do so without antibiotic resistance development. Using high-throughput screening assays of bacterial survival after treatment with high concentrations of ciprofloxacin, we have determined the prevalence of persisters in a large patient cohort using 460 longitudinal isolates of P. aeruginosa from 39 CF patients. Isolates were classed as high persister variants (Hip) if they regrew following antibiotic treatment in at least 75% of the experimental replicates. Strain genomic data, isolate phenotyping, and patient treatment records were integrated in a lineage-based analysis of persister formation and clinical impact. In total, 19% of the isolates were classified as Hip and Hip emergence increased over lineage colonization time within 22 Hip+ patients. Most Hip+ lineages produced multiple Hip isolates, but few Hip+ lineages were dominated by Hip. While we observed no strong signal of adaptive genetic convergence within Hip isolates, they generally emerged in parallel or following the development of ciprofloxacin resistance and slowed growth. Transient lineages were majority Hip-, while strains that persisted over a clinically diagnosed 'eradication' period were majority Hip+. Patients received indistinguishable treatment regimens before Hip emergence, but Hip+ patients overall were treated significantly more than Hip- patients, signaling repeated treatment failure. When subjected to in vivo-similar antibiotic dosing, a Hip isolate survived better than a non-Hip in a structured biofilm environment. In sum, the Hip phenotype appears to substantially contribute to long-term establishment of a lineage in the CF lung environment. Our results argue against the existence of a single dominant molecular mechanism underlying bacterial antibiotic persistence. We instead show that many routes, both phenotypic and genetic, are available for persister formation and consequent increases in strain fitness and treatment failure in CF airways.

Sputum microbiota in adults with CF associates with response to inhaled tobramycin

BACKGROUND

Inhaled tobramycin powder/solution (TIP/S) use has resulted in improved clinical outcomes in patients with cystic fibrosis (CF) with chronic Pseudomonas aeruginosa. However, TIP/S effect on the CF sputum microbiome has not been explored. We hypothesised that TIP/S has additional 'off-target' effects beyond merely P. aeruginosa and that baseline microbiome prior to initiation of therapy is associated with subsequent patient response.

METHODS

We drew sputum samples from a prospectively collected biobank. Patients were included if they had one sputum sample in the 18 months before and after TIP/S. Bacterial 16S rRNA gene profiling was used to characterise the sputum microbiome.

RESULTS

Forty-one patients met our inclusion criteria and 151 sputum samples were assessed. At baseline, median age was 30.4 years (IQR 24.2-35.2) and forced expiratory volume in 1 (FEV₁) second was 57% predicted (IQR 44-74). Nineteen patients were defined a priori as responders having no net decrease in FEV₁ in the year following TIP/S. No significant changes were observed in key microbiome metrics of alpha (within-sample) or beta (between-sample) diversity for samples collected before and after TIP/S. However, significant beta-diversity (Bray-Curtis) differences were noted at baseline between patients based on response status. Notably, responders were observed to have a higher abundance of Staphylococcus in pretherapy baseline samples.

CONCLUSIONS

Our longitudinal study demonstrates that the sputum microbiome of patients with CF is relatively stable following inhaled tobramycin over many months. Intriguingly, our findings suggest that baseline microbiome may associate with patient response to TIP/S-suggesting the sputum microbiome could be used to personalise therapy.

Pharmacokinetic/pharmacodynamic analysis of weight- and height-scaled tobramycin dosage regimens for patients with cystic fibrosis

OBJECTIVES

To determine the outcomes of weight- and height-based tobramycin dosing regimens for patients with cystic fibrosis (CF).

METHODS

A simulated dataset of 5000 patients based on 331 patients with CF was created using NONMEM. Pharmacokinetic (PK) parameters were derived for each patient from a published model using Monte Carlo simulation. The abilities of 10 and 12 mg/kg/day and 3 and 4 mg/cm/day to achieve standard and extended Cmax (20-30 and 20-40 mg/L) and AUC0-24 (80-120 and 80-150 mg·h/L) targets were evaluated. PK/pharmacodynamic (PK/PD) indices were a Cmax/MIC ratio ≥10 and an AUC0-24/MIC ratio ≥110. For these indices and a range of MICs, cumulative fractions of response (CFRs) for Pseudomonas aeruginosa were also determined.

RESULTS

More patients achieved standard Cmax and AUC0-24 targets with 3 mg/cm/day (64% and 62%, respectively) than with 10 mg/kg/day (43% and 48%, respectively). AUC0-24 estimates >120 mg·h/L were more common with weight-based dosing. With higher doses, 72% achieved high target peaks with 4 mg/cm/day and 65% with 12 mg/kg/day. For the Cmax/MIC index, the maximal MIC for the target microorganism was 2 mg/L with lower doses, 2.5 mg/L with higher doses and 0.5 mg/L for AUC0-24/MIC-based regimens. The CFR for all regimens was >90% for Cmax targets and 66% to 79% for AUC0-24 targets.

CONCLUSIONS

A tobramycin dose of 3 mg/cm/day rather than 10 mg/kg/day achieved similar PK/PD outcomes but dose and AUC0-24 ranges were narrower and the incidence of high AUC0-24 values was lower. Height-based doses should therefore be considered for patients with CF.

Population pharmacokinetics of amikacin in patients with pediatric cystic fibrosis

INTRODUCTION

Amikacin is commonly used in patients with pediatric cystic fibrosis (CF) for the treatment of pulmonary exacerbations. Amikacin efficacy is related to maximum plasma concentration/minimum inhibitory concentration (Cmax/MIC) ratio >8. Pharmacokinetic data in patients with pediatric CF are scarce. The aim of this study was to develop a population pharmacokinetic (PopPK) model describing amikacin disposition in patients with pediatric CF.

METHODS

CF patients under 18 years of age with pulmonary exacerbation who received amikacin were enrolled. Patients received different amikacin regimens (30 mg^-1  kg^-1  day^-1 every 8, 12, or 24 hours) depending on the patient's status and hospital protocols. Amikacin serum levels were obtained for therapeutic drug monitoring. PopPK model was developed using MONOLIX Suite-2018R1 (Lixoft).

RESULTS

A total of 39 patients (114 amikacin concentrations) were included in this study. Population estimates for the elimination rate constant (k) and the volume of distribution (V) were 0.541 hours^-1 and 0.451 L/kg, respectively. Between-subject and between-occasion variability were 53% and 16.5% for k and 31% and 22% for V, respectively. Bodyweight was a significant covariate associated with V. Based on simulations, almost 70% of the patients receiving 30 mg^-1  kg^-1  day^-1 every 24 hours would achieve a Cmax/MIC ratio >8 which is an appropriate therapeutic goal while no patient in the other two groups (Q8 and Q12) would achieve that objective.

CONCLUSIONS

The regimen of 30  mg^-1  kg^-1  day^-1 every 24 hours more adequately fulfilled the therapeutic target for amikacin. Although all our patients had good clinical results and a good adverse-events profile, further studies are necessary to redefine the optimal treatment strategy.

Once-daily versus multiple-daily dosing with intravenous aminoglycosides for cystic fibrosis

BACKGROUND

People with cystic fibrosis, who are chronically colonised with the organism Pseudomonas aeruginosa, often require multiple courses of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations. The properties of aminoglycosides suggest that they could be given in higher doses less often. This is an update of a previously published review.

OBJECTIVES

To assess the effectiveness and safety of once-daily versus multiple-daily dosing of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations in cystic fibrosis.

SEARCH METHODS

We searched the Cystic Fibrosis Specialist Register held at the Cochrane Cystic Fibrosis and Genetic Disorders Group's editorial base, comprising references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings.Date of the most recent search: 31 January 2019.We also searched online trial registries. Date of latest search: 25 February 2019.

SELECTION CRITERIA

All randomised controlled trials, whether published or unpublished, in which once-daily dosing of aminoglycosides has been compared with multiple-daily dosing in terms of efficacy or toxicity or both, in people with cystic fibrosis.

DATA COLLECTION AND ANALYSIS

The two authors independently selected the studies to be included in the review and assessed the risk of bias of each study; authors also assessed the quality of the evidence using the GRADE criteria. Data were independently extracted by each author. Authors of the included studies were contacted for further information. As yet unpublished data were obtained for one of the included studies.

MAIN RESULTS

We identified 15 studies for possible inclusion in the review. Five studies reporting results from a total of 354 participants (aged 5 to 50 years) were included in this review. All studies compared once-daily dosing with thrice-daily dosing. One cross-over trial had 26 participants who received the first-arm treatment but only 15 received the second arm. One study had a low risk of bias for all criteria assessed; the remaining included studies had a high risk of bias from blinding, but for other criteria were judged to have either an unclear or a low risk of bias.There was little or no difference between treatment groups in: forced expiratory volume in one second, mean difference (MD) 0.33 (95% confidence interval (CI) -2.81 to 3.48, moderate-quality evidence); forced vital capacity, MD 0.29 (95% CI -6.58 to 7.16, low-quality evidence); % weight for height, MD -0.82 (95% CI -3.77 to 2.13, low-quality evidence); body mass index, MD 0.00 (95% CI -0.42 to 0.42, low-quality evidence); or in the incidence of ototoxicity, relative risk 0.56 (95% CI 0.04 to 7.96, moderate-quality evidence). Once-daily treatment in children probably improved the percentage change in creatinine, MD -8.20 (95% CI -15.32 to -1.08, moderate-quality evidence), but showed no difference in adults, MD 3.25 (95% CI -1.82 to 8.33, moderate-quality evidence). The included trials did not report antibiotic resistance patterns or quality of life.

AUTHORS' CONCLUSIONS

Once- and three-times daily aminoglycoside antibiotics appear to be equally effective in the treatment of pulmonary exacerbations of cystic fibrosis. There is evidence of less nephrotoxicity in children.

Relationship between shift work and liver enzymes: a cross-sectional study based on the Korea National Health and Examination Survey (2007-2015)

Background

Shift work has well-known adverse effects on health. However, few studies have investigated the relationship between shift work and hepatic disorders. This study aimed to evaluate the association between shift work and abnormal level of liver enzymes.

Methods

The aggregated data from the 2007–2009, 2010–2012, and 2013–2015 cycles of the Korea National Health and Nutrition Examination Survey was used for this study. The χ² test and multiple logistic regression analysis were used to assess relationship between shift work and abnormal level of liver enzymes stratified by gender.

Results

The odds ratio (OR) of abnormal serum level of alanine aminotransferase (abnormal ALT) in female shift workers was higher with 1.31 (95% confidence interval: 1.00–1.71) compared with day workers after adjusting for covariates. After dividing into subgroups of the shift work pattern, the ORs of abnormal liver enzymes for each pattern compared with day work were not significantly higher.

Conclusions

This study provides limited support for the hypothesis that shift work is related to liver enzyme abnormalities, but offers some evidence in favor of the idea that shift work affects female workers more than males on abnormal ALT. Further studies are needed to define the relationship between shift work and abnormal liver enzymes to be carried out as well as the gender difference in the association.

Mutations causing low level antibiotic resistance ensure bacterial survival in antibiotic-treated hosts

In 474 genome sequenced Pseudomonas aeruginosa isolates from 34 cystic fibrosis (CF) patients, 40% of these harbor mutations in the mexZ gene encoding a negative regulator of the MexXY-OprM efflux pump associated with aminoglycoside and fluoroquinolone resistance. Surprisingly, resistance to aminoglycosides and fluoroquinolones of mexZ mutants was far below the breakpoint of clinical resistance. However, the fitness increase of the mutant bacteria in presence of the relevant antibiotics, as demonstrated in competition experiments between mutant and ancestor bacteria, showed that 1) very small phenotypic changes cause significant fitness increase with severe adaptive consequences, and 2) standardized phenotypic tests fail to detect such low-level variations. The frequent appearance of P. aeruginosa mexZ mutants in CF patients is directly connected to the intense use of the target antibiotics, and low-level antibiotic resistance, if left unnoticed, can result in accumulation of additional genetic changes leading to high-level resistance.

Polyester-based particles to overcome the obstacles of mucus and biofilms in the lung for tobramycin application under static and dynamic fluidic conditions

Pulmonary infections with Pseudomonas aeruginosa and Burkholderia cepacia complex (Bcc) are difficult to treat and related with high mortality in some diseases like cystic fibrosis due to the recurrent formation of biofilms. The biofilm formation hinders efficient treatment with inhaled antibiotics due to a low penetration of the antibiotics through the polyanionic biofilm matrix and increased antimicrobial resistance of the biofilm-embedded bacteria. In this study, tobramycin (Tb) was encapsulated in particles based on poly(d,l,-lactide-co-glycolide) (PLGA) and poly(ethylene glycol)-co-poly(d,l,-lactide-co-glycolide) diblock (PEG-PLGA) to overcome the biofilm barrier with particle sizes of 225-231 nm (nanoparticles) and 896-902 nm (microparticles), spherical shape and negative zeta potentials. The effectiveness against biofilms of P. aeruginosa and B. cepacia was strongly enhanced by the encapsulation under fluidic experimental condition as well as under static conditions in artificial mucus. The biofilm-embedded bacteria were killed by less than 0.77 mg/l encapsulated Tb, whereas 1,000 mg/l of free Tb or the bulk mixtures of Tb and the particles were ineffective against the biofilms. Moreover, encapsulated Tb was even effective against biofilms of the intrinsically aminoglycoside-resistant B. cepacia, indicating a supportive effect of PEG and PLGA on Tb. No cytotoxicity was detected in vitro in human lung epithelial cells with any formulation.

Spatiotemporal pharmacodynamics of meropenem- and tobramycin-treated Pseudomonas aeruginosa biofilms

Objectives

The selection and dose of antibiotic therapy for biofilm-related infections are based on traditional pharmacokinetic studies using planktonic bacteria. The objective of this study was to characterize the time course and spatial activity of human exposure levels of meropenem and tobramycin against Pseudomonas aeruginosa biofilms grown in an in vitro flow-chamber model.

Methods

Pharmacokinetic profiles of meropenem and tobramycin used in human therapy were administered to GFP-labelled P. aeruginosa PAO1 grown in flow chambers for 24 or 72 h. Images were acquired using confocal laser scanning microscopy throughout antibiotic treatment. Bacterial biomass was measured using COMSTAT and pharmacokinetic/pharmacodynamic models were fitted using NONMEM7.

Results

Meropenem treatment resulted in more rapid and sustained killing of both the 24 and 72 h PAO1 biofilm compared with tobramycin. Biofilm regrowth after antibiotic treatment occurred fastest with tobramycin. Meropenem preferentially killed subpopulations within the mushroom cap of the biofilms, regardless of biofilm maturity. The spatial killing by tobramycin varied with biofilm maturity. A tobramycin-treated 24 h biofilm resulted in live and dead cells detaching from the biofilm, while treatment of a 72 h biofilm preferentially killed subpopulations on the periphery of the mushroom stalk. Regrowth occurred primarily on the mushroom caps. Combination meropenem and tobramycin therapy resulted in rapid and efficient killing of biofilm cells, with a spatial pattern similar to meropenem alone.

Conclusions

Simulated human concentrations of meropenem and tobramycin in young and mature PAO1 biofilms exhibited differences in temporal and spatial patterns of killing and antibiotic tolerance development.

Melatonin Attenuates Dysregulation of the Circadian Clock Pathway in Mice With CCl4-Induced Fibrosis and Human Hepatic Stellate Cells

Dysregulation of the circadian clock machinery is a critical mechanism in the pathogenesis of fibrosis. This study aimed to investigate whether the antifibrotic effect of melatonin is associated with attenuation of circadian clock pathway disturbances in mice treated with carbon tetrachloride (CCl₄) and in human hepatic stellate cells line LX2. Mice received CCl₄ 5 μL/g body weight i.p. twice a week for 4 or 6 weeks. Melatonin was given at 5 or 10 mg/kg/day i.p., beginning 2 weeks after the start of CCl₄ administration. Treatment with CCl₄ resulted in fibrosis evidenced by the staining of α-smooth muscle actin (α-SMA) positive cells and a significant decrease of peroxisome proliferator-activated receptor (PPARα) expression. CCl₄ led to a lower expression of brain and muscle Arnt-like protein 1 (BMAL1), circadian locomotor output cycles kaput (CLOCK), period 1–3 (PER1, 2, and 3), cryptochrome 1 and 2 (CRY1 and 2) and the retinoic acid receptor-related orphan receptor (RORα). The expression of the nuclear receptor REV-ERBα showed a significant increase. Melatonin significantly prevented all these changes. We also found that melatonin (100 or 500 μM) potentiated the inhibitory effect of REV-ERB ligand SR9009 on α-SMA and collagen1 expression and increased the expression of PPARα in LX2 cells. Analysis of circadian clock machinery revealed that melatonin or SR9009 exposure upregulated BMAL1, CLOCK, PER2, CRY1, and RORα expression, with a higher effect of combined treatment. Findings from this study give new insight into molecular pathways accounting for the protective effect of melatonin in liver fibrosis.

Determination of Tobramycin in M9 Medium by LC-MS/MS: Signal Enhancement by Trichloroacetic Acid

It is well known that ion-pairing reagents cause ion suppression in LC-MS/MS methods. Here, we report that trichloroacetic acid increases the MS signal of tobramycin. To support studies of an in vitro pharmacokinetic/pharmacodynamic simulator for bacterial biofilms, an LC-MS/MS method for determination of tobramycin in M₉ media was developed. Aliquots of 25 μL M₉ media samples were mixed with the internal standard (IS) tobramycin-d₅ (5 µg/mL, 25 µL) and 200 µL 2.5% trichloroacetic acid. The mixture (5 µL) was directly injected onto a PFP column (2.0 × 50 mm, 3 µm) eluted with water containing 20 mM ammonium formate and 0.14% trifluoroacetic acid and acetonitrile containing 0.1% trifluoroacetic acid in a gradient mode. ESI⁺ and MRM with ion m/z 468 → 324 for tobramycin and m/z 473 → 327 for the IS were used for quantification. The calibration curve concentration range was 50-25000 ng/mL. Matrix effect from M₉ media was not significant when compared with injection solvents, but signal enhancement by trichloroacetic acid was significant (∼3 fold). The method is simple, fast, and reliable. Using the method, the in vitro PK/PD model was tested with one bolus dose of tobramycin.

Mathematical Modeling of Biofilm Structures Using COMSTAT Data

Mathematical modeling holds great potential for quantitatively describing biofilm growth in presence or absence of chemical agents used to limit or promote biofilm growth. In this paper, we describe a general mathematical/statistical framework that allows for the characterization of complex data in terms of few parameters and the capability to (i) compare different experiments and exposures to different agents, (ii) test different hypotheses regarding biofilm growth and interaction with different agents, and (iii) simulate arbitrary administrations of agents. The mathematical framework is divided to submodels characterizing biofilm, including new models characterizing live biofilm growth and dead cell accumulation; the interaction with agents inhibiting or stimulating growth; the kinetics of the agents. The statistical framework can take into account measurement and interexperiment variation. We demonstrate the application of (some of) the models using confocal microscopy data obtained using the computer program COMSTAT.

Once-daily versus multiple-daily dosing with intravenous aminoglycosides for cystic fibrosis

BACKGROUND

People with cystic fibrosis, who are chronically colonised with the organism Pseudomonas aeruginosa, often require multiple courses of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations. The properties of aminoglycosides suggest that they could be given in higher doses less often. This is an update of a previously published review.

OBJECTIVES

To assess the effectiveness and safety of once-daily versus multiple-daily dosing of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations in cystic fibrosis.

SEARCH METHODS

We searched the Cystic Fibrosis Specialist Register held at the Cochrane Cystic Fibrosis and Genetic Disorders Group's editorial base, comprising references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings.Date of the most recent search: 24 June 2016.

SELECTION CRITERIA

All randomised controlled trials, whether published or unpublished, in which once-daily dosing of aminoglycosides has been compared with multiple-daily dosing in terms of efficacy or toxicity or both, in people with cystic fibrosis.

DATA COLLECTION AND ANALYSIS

The two authors independently selected the studies to be included in the review and assessed the risk of bias of each study; authors also assessed the quality of the evidence using the GRADE criteria. Data were independently extracted by each author. Authors of the included studies were contacted for further information. As yet unpublished data were obtained for one of the included studies.

MAIN RESULTS

Fifteen studies were identified for possible inclusion in the review. Four studies reporting results from a total of 328 participants (aged 5 to 50 years) were included in this review. All studies compared once-daily dosing with thrice-daily dosing. One study had a low risk of bias for all criteria assessed; the remaining three included studies had a high risk of bias from blinding, but for other criteria were judged to have either an unclear or a low risk of bias.There was no significant difference between treatment groups in: forced expiratory volume in one second, mean difference 0.33 (95% confidence interval -2.81 to 3.48, moderate quality evidence); forced vital capacity, mean difference 0.29 (95% confidence interval -6.58 to 7.16, low quality evidence); % weight for height, mean difference -0.82 (95% confidence interval -3.77 to 2.13, low quality evidence); body mass index, mean difference 0.00 (95% confidence interval -0.42 to 0.42, low quality evidence); or in the incidence of ototoxicity, relative risk 0.56 (95% confidence interval 0.04 to 7.96, moderate quality evidence). The percentage change in creatinine significantly favoured once-daily treatment in children, mean difference -8.20 (95% confidence interval -15.32 to -1.08, moderate quality evidence), but showed no difference in adults, mean difference 3.25 (95% confidence interval -1.82 to 8.33, moderate quality evidence). The included trials did not report antibiotic resistance patterns or quality of life.

AUTHORS' CONCLUSIONS

Once- and three-times daily aminoglycoside antibiotics appear to be equally effective in the treatment of pulmonary exacerbations of cystic fibrosis. There is evidence of less nephrotoxicity in children.

Evaluation of a Once/Day Tobramycin Regimen to Achieve Target Concentrations in Adult Patients with Cystic Fibrosis

STUDY OBJECTIVE

To evaluate the success of an initial tobramycin dosing regimen to achieve target peak and trough concentrations in adult patients with pulmonary exacerbations of cystic fibrosis (CF).

DESIGN

Retrospective single-center medical record review.

SETTING

Large tertiary care academic medical center.

PATIENTS

A total of 186 patient encounters where 112 patients with CF were treated for acute pulmonary exacerbations with 10 mg/kg/day of tobramycin between January 1, 2009, and December 5, 2014.

MEASUREMENTS AND MAIN RESULTS

Baseline demographics, clinical characteristics, tobramycin data, and pharmacokinetic variables were collected. The primary outcome evaluated the success of the initial tobramycin dosing regimen in attaining the target peak concentration. Secondary end points were achievement of the target trough concentration, achievement of combined peak and trough targets, and incidence of nephrotoxicity. Bivariate and multivariate analyses were performed to evaluate factors associated with achieving target concentrations. Of the 186 patient encounters, 41% achieved the target peak with the first dosing regimen, 62% achieved a target trough, and 23% achieved the target peak and trough. Nephrotoxicity occurred in 10% of patient encounters. A body mass index (BMI) of 18.5-24.9 kg/m(2) was associated with higher odds of meeting the target peak compared with a BMI lower than 18.5 kg/m(2) (odds ratio [OR] 24.5; 95% confidence interval [CI] 5.2-117.2). Conversely, a BMI of 18.5-24.9 kg/m(2) was associated with lower odds of attaining the target trough compared with a BMI lower than 18.5 kg/m(2) (OR 0.16; 95% CI 0.05-0.56). Higher volume of distribution and elimination rate constants (Kel ) were associated with significantly lower odds of achieving the target peak. In addition, higher Kel values were associated with significantly higher odds of achieving the target trough.

CONCLUSIONS

The current initial tobramycin regimen did not achieve target serum tobramycin concentrations reliably. Optimization of the initial CF tobramycin dosing regimen is warranted.

Assessing Predictive Performance of Published Population Pharmacokinetic Models of Intravenous Tobramycin in Pediatric Patients

Several population pharmacokinetic models describe the dose-exposure relationship of tobramycin in pediatric patients. Before the implementation of these models in clinical practice for dosage adjustment, their predictive performance should be externally evaluated. This study tested the predictive performance of all published population pharmacokinetic models of tobramycin developed for pediatric patients with an independent patient cohort. A literature search was conducted to identify suitable models for testing. Demographic and pharmacokinetic data were collected retrospectively from the medical records of pediatric patients who had received intravenous tobramycin. Tobramycin exposure was predicted from each model. Predictive performance was assessed by visual comparison of predictions to observations, by calculation of bias and imprecision, and through the use of simulation-based diagnostics. Eight population pharmacokinetic models were identified. A total of 269 concentration-time points from 41 pediatric patients with cystic fibrosis were collected for external evaluation. Three models consistently performed best in all evaluations and had mean errors ranging from -0.4 to 1.8 mg/liter, relative mean errors ranging from 4.9 to 29.4%, and root mean square errors ranging from 47.8 to 66.9%. Simulation-based diagnostics supported these findings. Models that allowed a two-compartment disposition generally had better predictive performance than those that used a one-compartment disposition model. Several published models of the pharmacokinetics of tobramycin showed reasonable low levels of bias, although all models seemed to have some problems with imprecision. This suggests that knowledge of typical pharmacokinetic behavior and patient covariate values alone without feedback concentration measurements from individual patients is not sufficient to make precise predictions.

Extended-Interval Aminoglycoside Use in Cystic Fibrosis Exacerbation in Children and Young Adults: A Prospective Quality Improvement Project

This is a prospective quality improvement project for patients with cystic fibrosis who are 5 years of age and older who were admitted for intravenous antibiotic administration as part of treatment of cystic fibrosis exacerbation. The goal of this project was to compare the pharmacokinetics of once-daily versus thrice-daily aminoglycoside use when treating cystic fibrosis exacerbation in different age groups. Of the total of 119 patient encounters, 82.4% were started on once-daily dosing, and the remainder were started on thrice-daily dosing. Patients with pharmacokinetics allowing the continuation of once-daily dosing differed from patients who required a switch to thrice-daily dosing in terms of baseline forced expiratory volume in 1 second, forced expiratory flow from 25% to 75% of vital capacity, age, and body mass index (BMI) but were similar in BMI percentiles. The once-daily dosing group had higher mean 18-hour level, higher mean half-life, higher mean area under the curve, and lower mean elimination constant. This study showed that aminoglycoside clearance is higher in younger children.

Evolving roles of circadian rhythms in liver homeostasis and pathology

Circadian clock in mammals is determined by a core oscillator in the suprachiasmatic nucleus (SCN) of the hypothalamus and synchronized peripheral clocks in other tissues. The coherent timing systems could sustain robust output of circadian rhythms in response to the entrainment controlled environmentally. Disparate approaches have discovered that clock genes and clock-controlled genes (CCGs) exist in nearly all mammalian cell types and are essential for establishing the mechanisms and complexity of internal time-keeping systems. Accumulating evidence demonstrates that the control of homeostasis and pathology in the liver involves intricate loops of transcriptional and post-translational regulation of clock genes expression. This review will focus on the recent advances with great importance concerning clock rhythms linking liver homeostasis and diseases. We particularly highlight what is currently known of the evolving insights into the mechanisms underlying circadian clock . Eventually , findings during recent years in the field might prompt new circadian-related chronotherapeutic strategies for the diagnosis and treatment of liver diseases by coupling these processes.

The pharmacokinetics and toxicity of morning vs. evening tobramycin dosing for pulmonary exacerbations of cystic fibrosis: A randomised comparison

Background

Circadian variation in renal toxicity of aminoglycosides has been demonstrated in animal and human studies. People with CF are frequently prescribed aminoglycosides. Altered pharmacokinetics of aminoglycosides are predictive of toxicity.

Aim

To investigate whether the time of day of aminoglycoside administration modulates renal excretion of tobramycin and toxicity in children with CF. To determine whether circadian rhythms are disrupted in children with CF during hospital admission.

Methods

Children (age 5–18 years) with CF scheduled for tobramycin therapy were randomly allocated to receive tobramycin at 0800 or 2000 h. Serum tobramycin levels were drawn at 1 h and between 3.5 and 5 h post-infusion between days 5 and 9 of therapy. Melatonin levels were measured serially at intervals from 1800 h in the evening until 1200 h on the next day. Circadian rhythm was categorised as normal when dim light melatonin onset was demonstrated between 1800 and 2200 h and/or peak melatonin levels were observed during the night. Weight and spirometry were measured at the start and end of the therapy. Urinary biomarkers of kidney toxicity (KIM1, NAG, NGAL, IL-18 and CysC) were assayed at the start and end of the course of tobramycin.

Results

Eighteen children were recruited to the study. There were no differences in renal clearance between the morning and evening groups. The increase in urinary KIM-1 was greater in the evening dosage group compared to the morning group (mean difference, 0.73 ng/mg; 95% CI, 0.14 to 1.32; p = 0.018). There were no differences in the other urinary biomarkers. There was normal circadian rhythm in 7/11 participants (64%).

Conclusions

Renal elimination of tobramycin was not affected by the time of day of administration. Urinary KIM-1 raises the possibility of greater nephrotoxicity with evening administration. Four children showed disturbed circadian rhythm and high melatonin levels (ClinicalTrials.gov NCT01207245).

Intravenous antibiotics for pulmonary exacerbations in people with cystic fibrosis

BACKGROUND

Cystic fibrosis is a multi-system disease characterised by the production of thick secretions causing recurrent pulmonary infection, often with unusual bacteria. Intravenous antibiotics are commonly used in the treatment of acute deteriorations in symptoms (pulmonary exacerbations); however, recently the assumption that exacerbations are due to increases in bacterial burden has been questioned.

OBJECTIVES

To establish if intravenous antibiotics for the treatment of pulmonary exacerbations in people with cystic fibrosis improve short- and long-term clinical outcomes.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched the reference lists of relevant articles and reviews and ongoing trials registers.Date of last search of Cochrane trials register: 27 July 2015.

SELECTION CRITERIA

Randomised controlled trials and the first treatment cycle of cross-over studies comparing intravenous antibiotics (given alone or in an antibiotic combination) with placebo, inhaled or oral antibiotics for people with cystic fibrosis experiencing a pulmonary exacerbation.

DATA COLLECTION AND ANALYSIS

The authors assessed studies for eligibility and risk of bias and extracted data.

MAIN RESULTS

We included 40 studies involving 1717 participants. The quality of the included studies was largely poor and, with a few exceptions, these comprised of mainly small, inadequately reported studies.When comparing treatment with a single antibiotic to a combined antibiotic regimen, those participants receiving a combination of antibiotics experienced a greater improvement in lung function when considered as a whole group across a number of different measurements of lung function, but with very low quality evidence. When limited to the four placebo-controlled studies (n = 214), no difference was observed, again with very low quality evidence. With regard to the review's remaining primary outcomes, there was no effect upon time to next exacerbation and no studies in any comparison reported on quality of life. There were no effects on the secondary outcomes weight or adverse effects. When comparing specific antibiotic combinations there were no significant differences between groups on any measure. In the comparisons between intravenous and nebulised antibiotic or oral antibiotic (low quality evidence), there were no significant differences between groups on any measure. No studies in any comparison reported on quality of life.

AUTHORS' CONCLUSIONS

The quality of evidence comparing intravenous antibiotics with placebo is poor. No specific antibiotic combination can be considered to be superior to any other, and neither is there evidence showing that the intravenous route is superior to the inhaled or oral routes. There remains a need to understand host-bacteria interactions and in particular to understand why many people fail to fully respond to treatment.

Pharmacokinetic/pharmacodynamic modelling approaches in paediatric infectious diseases and immunology

Pharmacokinetic/pharmacodynamic (PKPD) modelling is used to describe and quantify dose-concentration-effect relationships. Within paediatric studies in infectious diseases and immunology these methods are often applied to developing guidance on appropriate dosing. In this paper, an introduction to the field of PKPD modelling is given, followed by a review of the PKPD studies that have been undertaken in paediatric infectious diseases and immunology. The main focus is on identifying the methodological approaches used to define the PKPD relationship in these studies. The major findings were that most studies of infectious diseases have developed a PK model and then used simulations to define a dose recommendation based on a pre-defined PD target, which may have been defined in adults or in vitro. For immunological studies much of the modelling has focused on either PK or PD, and since multiple drugs are usually used, delineating the relative contributions of each is challenging. The use of dynamical modelling of in vitro antibacterial studies, and paediatric HIV mechanistic PD models linked with the PK of all drugs, are emerging methods that should enhance PKPD-based recommendations in the future.

Once-daily versus multiple-daily dosing with intravenous aminoglycosides for cystic fibrosis

BACKGROUND

People with cystic fibrosis, who are chronically colonised with the organism Pseudomonas aeruginosa, often require multiple courses of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations. The properties of aminoglycosides suggest that they could be given in higher doses less often.

OBJECTIVES

To assess the effectiveness and safety of once-daily versus multiple-daily dosing of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations in cystic fibrosis.

SEARCH METHODS

We searched the Cystic Fibrosis Specialist Register held at the Cochrane Cystic Fibrosis and Genetic Disorders Group's editorial base, comprising references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings.Date of the most recent search: 25 November 2013.

SELECTION CRITERIA

All randomised controlled trials, whether published or unpublished, in which once-daily dosing of aminoglycosides has been compared with multiple-daily dosing in terms of efficacy or toxicity or both, in people with cystic fibrosis.

DATA COLLECTION AND ANALYSIS

The two authors independently selected the studies to be included in the review and assessed the risk of bias of each study. Data were independently extracted by each author. Authors of the included studies were contacted for further information. As yet unpublished data were obtained for one of the included studies.

MAIN RESULTS

Fifteen studies were identified for possible inclusion in the review. Four studies reporting results from a total of 328 participants were included in this review. All studies compared once-daily dosing with thrice-daily dosing. One study had a low risk of bias for all criteria assessed; the remaining three included studies had a high risk of bias from blinding, but for other criteria were judged to have either an unclear or a low risk of bias.There was no significant difference between treatment groups in: forced expiratory volume at one second, mean difference 0.33 (95% confidence interval -2.81 to 3.48); forced vital capacity, mean difference 0.29 (95% confidence interval -6.58 to 7.16); % weight for height, mean difference -0.82 (95% confidence interval -3.77 to 2.13); body mass index, mean difference 0.00 (95% confidence interval -0.42 to 0.42); or in the incidence of ototoxicity, relative risk 0.56 (95% confidence interval 0.04 to 7.96). The percentage change in creatinine significantly favoured once-daily treatment in children, mean difference -8.20 (95% confidence interval -15.32 to -1.08), but showed no difference in adults, mean difference 3.25 (95% confidence interval -1.82 to 8.33).

AUTHORS' CONCLUSIONS

Once- and three-times daily aminoglycoside antibiotics appear to be equally effective in the treatment of pulmonary exacerbations of cystic fibrosis. There is evidence of less nephrotoxicity in children.

Optimization of anti-pseudomonal antibiotics for cystic fibrosis pulmonary exacerbations: V. Aminoglycosides

Intravenous (IV) anti-pseudomonal aminoglycosides (i.e., amikacin and tobramycin) have been shown to be tolerable and effective in the treatment of acute pulmonary exacerbations (APEs) in both pediatric and adult patients with cystic fibrosis. The aim of this review is to provide an evidence-based summary of pharmacokinetic/pharmacodynamic, tolerability, and efficacy studies utilizing IV amikacin, gentamicin, and tobramycin in the treatment of APE and to highlight areas where further investigation is needed. The Cystic Fibrosis Foundation Pulmonary Guidelines recommend that once-daily administration of aminoglycosides is preferred over three times per day in the treatment of an APE. The literature supports dosing ranges for amikacin and tobramycin of 30-35 and 7-15 mg/kg/day, respectively, given once daily, with subsequent doses determined by therapeutic drug concentration monitoring. The literature does not support the routine use of gentamicin in the treatment of APE due to a lack of studies showing efficacy and evidence indicating an increased risk of nephrotoxicity. Further studies are needed to determine the optimal dosing strategy of amikacin in the treatment of an APE, and to further identify risk factors and determinants that influence the development of P. aeruginosa resistance with once-daily administration of tobramycin.

Population pharmacokinetics of tobramycin in patients with and without cystic fibrosis

BACKGROUND AND OBJECTIVES

While several studies have examined the pharmacokinetics of tobramycin in patients with cystic fibrosis (CF), there is no consensus on whether they differ in patients with and without CF. The objectives of this study were to identify covariates which explain pharmacokinetic variability and to examine whether having the disease CF in itself alters these relationships and drug dose requirements.

METHODS

To investigate this issue, a population pharmacokinetic meta-analysis of data from eight centres was undertaken. NONMEM(®) 7.2 was used to analyse the data, which comprised 4,514 concentration-time measurements from 465 adults and children with CF and 1,095 concentration-time measurements from 267 adults and children without CF.

RESULTS

Tobramycin disposition was well described by a two-compartment model with first-order elimination. Patient age, fat-free mass, serum creatinine concentration and sex were identified as significant covariates in the final model. Fat-free mass was superior to total bodyweight as a descriptor of clearance, volume of distribution of the central and peripheral compartments and inter-compartmental clearance. CF as an independent disease-specific factor had no significant influence on the pharmacokinetics of tobramycin at any stage during covariate model building. An optimal dose of 11 mg/kg every 24 h was defined for CF patients using a utility function approach.

CONCLUSION

The pharmacokinetics of tobramycin do not differ significantly in CF patients compared with patients without CF when subject age, fat-free mass, sex and renal function are taken into consideration. Variations in tobramycin dosing between CF and non-CF patients should therefore reflect target concentrations or exposures based on differences in expected pathogen sensitivity and not the presence of CF.

Evaluation of serum concentrations achieved with an empiric once-daily tobramycin dosage regimen in children and adults with cystic fibrosis

OBJECTIVES

To assess the ability of an empiric once-daily dosing (ODD) tobramycin regimen to achieve desired serum concentrations in patients with cystic fibrosis (CF); to determine an optimal dosage regimen, using pharmacodynamic parameters; and to evaluate clinical response, adverse effects, and patient/parent satisfaction with ODD.

METHODS

This was a prospective single-center trial in patients with CF who are 5 years of age and older requiring intravenous antibiotics. Tobramycin, 10 mg/kg every 24 hours, was infused over 60 minutes, and two serum concentrations were analyzed using 1-compartment pharmacokinetic modeling. Simulations were performed to identify dosage regimens that maximized desired pharmacodynamic parameters. Other data included demographics, symptoms, spirometry, adverse events, and satisfaction with ODD.

RESULTS

A total of 14 children and 11 adults completed the study. Empiric doses resulted in mean peak tobramycin concentrations of 28.7 ± 5.5 mg/L and undetectable trough concentrations. Only 42% of patients achieved desired peak serum concentrations (20-30 mg/L) with the empiric regimen. A regimen of 12 mg/kg every 24 hours would achieve modified pharmacodynamic goals with an acceptable peak range of 20 to 35 mg/L. Forced expiratory volume in 1 second improved in 15 of 20 (75%) patients with ODD. Two patients experienced reversible vestibular adverse effects attributed to tobramycin. All patients were satisfied or very satisfied with ODD because of convenience and ease of use.

CONCLUSIONS

An empiric tobramycin regimen of 10 mg/kg every 24 hours did not achieve desired serum concentrations for most patients, although all patients demonstrated clinical improvement. Desired tobramycin concentrations with modified pharmacodynamic goals could be achieved by using an empiric dosage of 12 mg/kg every 24 hours. Prospective evaluation of this regimen with individualized patient monitoring is needed to ensure safety and efficacy and to monitor the effects on microbial resistance patterns.

Once-daily versus multiple-daily dosing with intravenous aminoglycosides for cystic fibrosis

BACKGROUND

People with cystic fibrosis, who are chronically colonised with the organism Pseudomonas aeruginosa, often require multiple courses of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations. The properties of aminoglycosides suggest that they could be given in higher doses less often.

OBJECTIVES

To assess the effectiveness and safety of once-daily versus multiple-daily dosing of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations in cystic fibrosis.

SEARCH METHODS

We searched the Cystic Fibrosis Specialist Register held at the Cochrane Cystic Fibrosis and Genetic Disorders Group's editorial base, comprising references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings.Date of the most recent search: 29 September 2011.

SELECTION CRITERIA

All randomised controlled trials, whether published or unpublished, in which once-daily dosing of aminoglycosides has been compared with multiple-daily dosing in terms of efficacy or toxicity or both, in people with cystic fibrosis.

DATA COLLECTION AND ANALYSIS

The two authors independently selected the studies to be included in the review and assessed methodological quality of each study. Data were independently extracted by each author. Authors of the included studies were contacted for further information. As yet unpublished data were obtained for one of the included studies.

MAIN RESULTS

Sixteen studies were identified for possible inclusion in the review. Four studies reporting results from a total of 328 participants were included in this review. All studies compared once-daily dosing with thrice-daily dosing. There was no significant difference between treatment groups in: forced expiratory volume at one second, mean difference 0.33 (95% confidence interval -2.81 to 3.48); forced vital capacity, mean difference 0.29 (95% confidence interval -6.58 to 7.16); % weight for height, mean difference -0.82 (95% confidence interval -3.77 to 2.13); body mass index, mean difference 0.00 (95% confidence interval -0.42 to 0.42); or in the incidence of ototoxicity, relative risk 0.56 (95% confidence interval 0.04 to 7.96). The percentage change in creatinine significantly favoured once-daily treatment in children, mean difference -8.20 (95% confidence interval -15.32 to -1.08), but showed no difference in adults, mean difference 3.25 (95% confidence interval -1.82 to 8.33).

AUTHORS' CONCLUSIONS

Once- and three-times daily aminoglycoside antibiotics appear to be equally effective in the treatment of pulmonary exacerbations of cystic fibrosis. There is evidence of less nephrotoxicity in children.

Current use for old antibacterial agents: polymyxins, rifamycins, and aminoglycosides

This article reviews three classes of antibacterial agents that are uncommonly used in bacterial infections and therefore can be thought of as special-use agents. The polymyxins are reserved for gram-negative bacilli that are resistant to virtually all other classes of drugs. Rifampin is used therapeutically, occasionally as a companion drug in treatment of refractory gram-positive coccal infections, especially those involving foreign bodies. Rifaximin is a new rifamycin that is a strict enteric antibiotic approved for treatment of traveler's diarrhea and is showing promise as a possible agent for refractory Clostridium difficile infections. The aminoglycosides are used mainly as companion drugs for the treatment of resistant gram-negative bacillary infections and for gram-positive coccal endocarditis.

Side effects of aminoglycosides on the kidney, ear and balance in cystic fibrosis

Aminoglycoside antibiotics are a central component of the treatment of pulmonary exacerbations of cystic fibrosis (CF) and slow the decline in lung function which ultimately causes the death of most patients. The prognosis of CF has improved, and thus side effects of treatments have become increasingly important. Observational studies suggest that the morbidity from side effects of aminoglycosides is disturbingly common, and that aggressive treatment may lead to more side effects. This review of the current literature on side effects of aminoglycosides considers the pathophysiological mechanisms, epidemiology and risk factors, investigation of side effects and preventative strategies. Treatments which have shown early promise are identified and areas of future research are discussed.

Current use for old antibacterial agents: polymyxins, rifamycins, and aminoglycosides

This article reviews three classes of antibacterial agents that are uncommonly used in bacterial infections and therefore can be thought of as special-use agents. The polymyxins are reserved for gram-negative bacilli that are resistant to virtually all other classes of drugs. Rifampin is used therapeutically, occasionally as a companion drug in treatment of refractory gram-positive coccal infections, especially those involving foreign bodies. Rifaximin is a new rifamycin that is a strict enteric antibiotic approved for treatment of traveler's diarrhea and is showing promise as a possible agent for refractory Clostridium difficile infections. The aminoglycosides are used mainly as companion drugs for the treatment of resistant gram-negative bacillary infections and for gram-positive coccal endocarditis.

Once-daily versus multiple-daily dosing with intravenous aminoglycosides for cystic fibrosis

BACKGROUND

People with cystic fibrosis, who are chronically colonised with the organism Pseudomonas aeruginosa, often require multiple courses of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations. The properties of aminoglycosides suggest that they could be given in higher doses less often.

OBJECTIVES

To assess the effectiveness and safety of once-daily versus multiple-daily dosing of intravenous aminoglycoside antibiotics for the management of pulmonary exacerbations in cystic fibrosis.

SEARCH STRATEGY

We searched the Cystic Fibrosis Specialist Register held at the Cochrane Cystic Fibrosis and Genetic Disorders Group's editorial base, comprising references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings.Date of the most recent search: 19 August 2008.

SELECTION CRITERIA

All randomised controlled trials, whether published or unpublished, in which once-daily dosing of aminoglycosides has been compared with multiple-daily dosing in terms of efficacy or toxicity or both, in people with cystic fibrosis.

DATA COLLECTION AND ANALYSIS

The two authors independently selected the studies to be included in the review and assessed methodological quality of each study. Data were independently extracted by each author. Authors of the included studies were contacted for further information. As yet unpublished data were obtained for one of the included studies.

MAIN RESULTS

Thirteen studies were identified for possible inclusion in the review. Four studies reporting results from a total of 328 participants were included in this review. All studies compared once-daily dosing with thrice-daily dosing. There was no significant difference between treatment groups in: forced expiratory volume at one second, mean difference (MD) 0.33 (95% confidence interval (CI) -2.81 to 3.48); forced vital capacity, MD 0.29 (95% CI -6.58 to 7.16); % weight for height, MD -0.82 (95% CI -3.77 to 2.13); body mass index, MD 0.00 (95% CI -0.42 to 0.42); or in the incidence of ototoxicity, relative risk 0.56 (95% CI 0.04 to 7.96). The percentage change in creatinine significantly favoured once-daily treatment in children, MD -8.20 (95% CI -15.32 to -1.08), but showed no difference in adults, MD 3.25 (95% CI -1.82 to 8.33).

AUTHORS' CONCLUSIONS

Once and three times daily aminoglycoside antibiotics appear to be equally effective in the treatment of pulmonary exacerbations of cystic fibrosis. There is evidence of less nephrotoxicity in children.