Population Pharmacokinetics of Fluconazole in Premature Infants with Birth Weights Less than 750 Grams

Physicochemical Characteristics of Antimicrobials and Practical Recommendations for Intravenous Administration: A Systematic Review

Most antimicrobial drugs need an intravenous (IV) administration to achieve maximum efficacy against target pathogens. IV administration is related to complications, such as tissue infiltration and thrombo-phlebitis. This systematic review aims to provide practical recommendations about diluent, pH, osmolarity, dosage, infusion rate, vesicant properties, and phlebitis rate of the most commonly used antimicrobial drugs evaluated in randomized controlled studies (RCT) till 31 March 2023. The authors searched for available IV antimicrobial drugs in RCT in PUBMED EMBASE®, EBSCO® CINAHL®, and the Cochrane Controlled Clinical trials. Drugs' chemical features were searched online, in drug data sheets, and in scientific papers, establishing that the drugs with a pH of <5 or >9, osmolarity >600 mOsm/L, high incidence of phlebitis reported in the literature, and vesicant drugs need the adoption of utmost caution during administration. We evaluated 931 papers; 232 studies were included. A total of 82 antimicrobials were identified. Regarding antibiotics, 37 reach the "caution" criterion, as well as seven antivirals, 10 antifungals, and three antiprotozoals. In this subgroup of antimicrobials, the correct vascular access device (VAD) selection is essential to avoid complications due to the administration through a peripheral vein. Knowing the physicochemical characteristics of antimicrobials is crucial to improve the patient's safety significantly, thus avoiding administration errors and local side effects.

The efficacy and safety of fluconazole in preventing invasive fungal infection in very low birth weight infants: a systematic review and meta-analysis

This meta-analysis aimed to assess the efficacy and safety of fluconazole for the prevention of invasive fungal infections (IFI) in very low birth weight infants (VLBWI) and to provide a basis for the clinical use. A detailed search of Pubmed, Embase, Cochrane Library and other databases was performed to carefully screen eligible randomized controlled clinical studies to assess the safety and efficacy of fluconazole in very low birth weight infants in terms of the incidence of invasive fungal infections, fungal colonization rate, and mortality. Our research indicated that the application of fluconazole did not result in intolerable adverse reactions in patients. Fluconazole is effective in preventing invasive fungal infections in very low birth weight infants without serious adverse effects. The dose and frequency of fluconazole in very low birth weight infants still needs to be evaluated in consequent studies.

Pharmacokinetic comparability between two populations using nonlinear mixed effect models: a Monte Carlo study

'Are two populations the same or are they different' is a question that is often faced in clinical pharmacology trials e.g., a pharmacokinetic trial studying a particular drug in racially different groups. To address this question, concentration-time data were simulated from a reference and test population, where in the latter the clearance, sample size, and sampling design were systematically varied. It was of interest to determine whether the estimates of clearance from the two groups were the same or different. Two approaches were used to estimate the empirical Bayes estimates (EBEs) for clearance. One approach developed a population pharmacokinetic model for the reference population and the EBEs for the reference population were estimated from this model. The parameters of the reference population were fixed to their maximum likelihood estimates. The model was then applied to the test population dataset to estimate the EBEs of the test population using the MAXEVAL = 0 option in NONMEM. A second approach, the theta approach, combined the reference and test datasets into a single dataset and used population as a covariate in the model; the EBEs were estimated from this combined model. The power and type I error rate of each approach were calculated for each treatment combination using a variety of statistical tests to determine whether there was a difference in the distribution of the EBEs in the reference population compared to the test population. Our results suggest that either MAXEVAL or theta approaches can be used with informative sampling designs. In addition to reasonable power and type I error, both approaches gave almost identical results under a dense sampling design. To statistically compare the distribution of EBEs of pharmacokinetic parameters from a reference group to that of a test group, a T-test and DTS eCDF test are equally useful.

Updates in the Pharmacologic Prophylaxis and Treatment of Invasive Candidiasis in the Pediatric and Neonatal Intensive Care Units

Purpose of review

The goal of this review was to provide an update on the prevention and treatment options for invasive candidiasis (IC) in the neonatal intensive care unit (NICU) and pediatric intensive care unit (PICU).

Recent findings

Studies have further validated the use of fluconazole for IC prophylaxis among high-risk patients in the NICU. It remains unclear if prophylaxis leads to resistance development and the ideal dosage regimen is still not clear. Recent studies have been published comparing caspofungin and micafungin to amphotericin B and illustrated similar efficacy outcomes in the NICU. Micafungin now has approval from the United States Food and Drug Administration (FDA) for use in infants < 4 months of age. Prophylactic strategies in the PICU could include zinc and vitamin D. Anidulafungin has recent non-comparative data supporting use in pediatric patients older than 1 month of age and also has a recent FDA approval for use in children 1 month of age and older.

Summary

Fluconazole prophylaxis remains a reasonable strategy in select NICU patients, although further analyses of resistance and the optimal dosage regimen are needed. Echinocandins are potential therapeutic options for non-meningitis or urinary tract infections in both the neonatal and pediatric population.

Optimisation of fluconazole therapy for the treatment of invasive candidiasis in preterm infants

INTRODUCTION

Fluconazole is an important antifungal in the prevention and treatment of invasive Candida infections in neonates, even though its use in preterm infants is still off-label. Here, we performed a population pharmacokinetic study on fluconazole in preterm neonates in order to optimise dosing through the identified predictive patient characteristics.

METHODS

Fluconazole concentrations obtained from preterm infants from two studies were pooled and analysed using NONMEM V.7.3. The developed model was used to evaluate current dosing practice. A therapeutic dosing strategy aiming to reach a minimum target exposure of 400 and 200 mg×hour/L per 24 hours for fluconazole-susceptible C. albicans meningitis and other systemic infections, respectively, was developed.

RESULTS

In 41 preterm neonates with median (range) gestational age 25.3 (24.0-35.1) weeks and median postnatal age (PNA) at treatment initiation 1.4 (0.2-32.5) days, 146 plasma samples were collected. A one-compartment model described the data best, with an estimated clearance of 0.0147 L/hour for a typical infant of 0.87 kg with a serum creatinine concentration of 60 µmol/L and volume of distribution of 0.844 L. Clearance was found to increase with 16% per 100 g increase in actual body weight, and to decrease with 12% per 10 µmol/L increase in creatinine concentration once PNA was above 1 week. Dose adjustments based on serum creatinine and daily dosing are required for therapeutic target attainment.

CONCLUSION

In preterm neonates, fluconazole clearance is best predicted by actual body weight and serum creatinine concentration. Therefore, fluconazole dosing should not only be based on body weight but also on creatinine concentration to achieve optimal exposure in all infants.

ETHICS STATEMENT

The Erasmus MC ethics review board approved the protocol of the DINO Study (MEC-2014-067) and the Radboud UMC ethics review board waived the need for informed consent for cohort 2 (CMO-2021-8302). Written informed consent from parents/legal guardians was obtained prior to study initiation.

Fluconazole Population Pharmacokinetics after Fosfluconazole Administration and Dosing Optimization in Extremely Low-Birth-Weight Infants

A prospective single-center study was conducted to characterize the pharmacokinetics (PK) of fluconazole (FLCZ) in extremely low-birth-weight infants (ELBWIs) who received fosfluconazole (F-FLCZ). Intravenous F-FLCZ was administered at a dose of 3 mg/kg of body weight every 72 h during the first 2 weeks of life, every 48 h during the third and fourth weeks of life, and every 24 h after 5 weeks of life. Blood samples from ELBWIs treated with F-FLCZ were collected using scavenged samples. The concentration of FLCZ was determined using liquid chromatography-tandem mass spectrometry. The population pharmacokinetic model was established using Phenix NLME 8.2 software. In total, 18 ELBWIs were included in this analysis. Individual PK parameters were determined by a one-compartment analysis with first-order conversion. Postmenstrual age (PMA), serum creatinine (SCr), and alkaline phosphatase were considered covariates for clearance (CL). The mean population CL and the volume of distribution were 0.011 L/h/kg^0.75 and 0.95 L/kg, respectively. Simulation assessments with the final model revealed that the current regimen (3 mg/kg every 72 h) could achieve the proposed target FLCZ trough concentration (>2 μg/mL) in 43.3% and 72.2% of infants with a PMA of ≥37 and 30 to 36 weeks, respectively, and an SCr level of <0.5 mg/dL. Shortened dosing intervals (every 48 or 24 h) might improve the probability of target attainment. This study was the first to assess the PK of F-FLCZ in ELBWI, as well as the first to provide fundamental information about FLCZ exposure after F-FLCZ administration, with the goal of facilitating dose optimization in the ELBWI population.

IMPORTANCE Invasive fungal infection is an important cause of mortality and morbidity in very preterm or very-low-birth-weight infants. In order to limit the risk of invasive fungal infections in this population, the administration of fluconazole is generally recommended for extremely low-birth-weight infants admitted to a neonatal intensive care unit with a Candida species colonization prevalence rate of >10%, under the guidelines of the Infectious Diseases Society of America. Fosfluconazole can reduce the volume of solution required for intravenous therapy compared to fluconazole because it has increased solubility, which is a major advantage for infants undergoing strict fluid management. To date, no study has demonstrated the fluconazole pharmacokinetics after fosfluconazole administration in neonates and infants, and this needs to be clarified. Here, we characterized the pharmacokinetics of fluconazole in extremely low-birth-weight infants who received F-FLCZ and explored the appropriate dosage in this patient population.

The Blind Spot of Pharmacology: A Scoping Review of Drug Metabolism in Prematurely Born Children

The limit for possible survival after extremely preterm birth has steadily improved and consequently, more premature neonates with increasingly lower gestational age at birth now require care. This specialized care often include intensive pharmacological treatment, yet there is currently insufficient knowledge of gestational age dependent differences in drug metabolism. This potentially puts the preterm neonates at risk of receiving sub-optimal drug doses with a subsequent increased risk of adverse or insufficient drug effects, and often pediatricians are forced to prescribe medication as off-label or even off-science. In this review, we present some of the particularities of drug disposition and metabolism in preterm neonates. We highlight the challenges in pharmacometrics studies on hepatic drug metabolism in preterm and particularly extremely (less than 28 weeks of gestation) preterm neonates by conducting a scoping review of published literature. We find that >40% of included studies failed to report a clear distinction between term and preterm children in the presentation of results making direct interpretation for preterm neonates difficult. We present summarized findings of pharmacokinetic studies done on the major CYP sub-systems, but formal meta analyses were not possible due the overall heterogeneous approaches to measuring the phase I and II pathways metabolism in preterm neonates, often with use of opportunistic sampling. We find this to be a testament to the practical and ethical challenges in measuring pharmacokinetic activity in preterm neonates. The future calls for optimized designs in pharmacometrics studies, including PK/PD modeling-methods and other sample reducing techniques. Future studies should also preferably be a collaboration between neonatologists and clinical pharmacologists.

Review of Scavenged Sampling for Sustainable Therapeutic Drug Monitoring: Do More With Less

PURPOSE

Innovative and sustainable sampling strategies for bioanalytical quantification of drugs and metabolites have gained considerable interest. Scavenging can be stratified as a sustainable sampling strategy using residual material because it aligns with the green principles of waste reduction and sampling optimization. Scavenged sampling includes all biological fluids' (eg, blood, liquor, and urine) leftover from standard clinical care. This review elaborates on the past and current landscape of sustainable sampling within therapeutic drug monitoring, with a focus on scavenged sampling.

METHODS

In February 2021, 4 databases were searched to assess the literature on the clinical use of innovative and sustainable sampling techniques without applying publication date restrictions. Studies reporting the clinical use of scavenged blood sampling and bridging studies of scavenged sampling and normal blood sampling were eligible for inclusion.

RESULTS

Overall, 19 eligible studies concerning scavenged sampling were identified from 1441 records. Scavenged sampling is mainly applied in the pediatric population, although other patient groups may benefit from this strategy. The infrastructure required for scavenged sampling encounters several challenges, including logistic hurdles, storage and handling conditions, and documentation errors. A workflow is proposed with identified opportunities that guide the implementation of scavenged sampling.

CONCLUSIONS

This review presents current evidence on the clinical use of scavenged sampling strategies. Scavenged sampling can be a suitable approach for drug quantification to improve dosage regimens, perform pharmacokinetic studies, and explore the value of therapeutic drug monitoring without additional sample collection.

Developing a SWATH capillary LC-MS/MS method for simultaneous therapeutic drug monitoring and untargeted metabolomics analysis of neonatal plasma

Most medications prescribed to neonatal patients are off-label uses. The pharmacokinetics and pharmacodynamics of drugs differ significantly between neonates and adults. Therefore, personalized pharmacotherapy guided by therapeutic drug monitoring (TDM) and drug response biomarkers are particularly beneficial to neonatal patients. Herein, we developed a capillary LC-MS/MS metabolomics method using a SWATH-based data-independent acquisition strategy for simultaneous targeted and untargeted metabolomics analysis of neonatal plasma samples. We applied the method to determine the global plasma metabolomics profiles and quantify the plasma concentrations of five drugs commonly used in neonatal intensive care units, including ampicillin, caffeine, fluconazole, vancomycin, and midazolam and its active metabolite α-hydroxymidazolam, in neonatal patients. The method was successfully validated and found to be suitable for the TDM of the drugs of interest. Moreover, the global metabolomics analysis revealed plasma metabolite features that could differentiate preterm and full-term neonates. This study demonstrated that the SWATH-based capillary LC-MS/MS metabolomics approach could be a powerful tool for simultaneous TDM and the discovery of neonatal plasma metabolite biomarkers.

Challenges in conducting paediatric trials with off-patent drugs

Introduction

For more than two decades several initiatives have emerged to increase recruitment of paediatric patients in drug trials. While trials of newly approved drugs have successfully included paediatric patients in their drug development plan, the collection of safety and efficacy data in paediatric patients treated with off-patent drugs poses a major challenge.

Aim

This paper aims to draw attention to problems and solutions across countries in investigator-initiated trials with off-patent drugs and recommendations for improvement.

Discussion

Off-patent drugs represent a particular challenge when they are included in a paediatric trial; these trials are frequently investigator-initiated and have limited resources, off-patent drugs are used in clinical settings and the trial protocol must accommodate e.g. flexible dosing and specimen sampling schedules, off-patent drugs typically exist in few formulations and concentrations which necessitates special or imported formulations. Paediatric trials are in some countries confined by e.g. consent from both parents, regardless of whether the Investigational Medicinal Product (IMP) is a well-known drug or a new experimental drug.

Conclusion

Facilitation of research in off-patent drugs can improve evidence-based and safe treatment for the paediatric population. The following supportive initiatives are recommended: Harmonised regulatory change that improves the consent process in low risk trials to prevent inadequate recruitment. Pharmaceutical expertise should be prioritized to secure the best choice of IMP and supply. Constant focus on flexibility in design to accommodate a multifaceted paediatric population and ensure that trial protocols fit in well with routine clinical care and family life.

Preterm Physiologically Based Pharmacokinetic Model. Part II: Applications of the Model to Predict Drug Pharmacokinetics in the Preterm Population

BACKGROUND

Preterm neonates are usually not part of a traditional drug development programme, however they are frequently administered medicines. Developing modelling and simulation tools, such as physiologically based pharmacokinetic (PBPK) models that incorporate developmental physiology and maturation of drug metabolism, can be used to predict drug exposure in this group of patients, and may help to optimize drug dose adjustment.

OBJECTIVE

The aim of this study was to assess and verify the predictability of a preterm PBPK model using compounds that undergo diverse renal and/or hepatic clearance based on the knowledge of their disposition in adults.

METHODS

A PBPK model was developed in the Simcyp Simulator V17 to predict the pharmacokinetics (PK) of drugs in preterm neonates. Drug parameters for alfentanil, midazolam, caffeine, ibuprofen, gentamicin and vancomycin were collated from the literature. Predicted PK parameters and profiles were compared against the observed data.

RESULTS

The preterm PBPK model predicted the PK changes of the six compounds using ontogeny functions for cytochrome P450 (CYP) 1A2, CYP2C9 and CYP3A4 after oral and intravenous administrations. For gentamicin and vancomycin, the maturation of renal function was able to predict the exposure of these two compounds after intravenous administration. All PK parameter predictions were within a twofold error criteria.

CONCLUSION

While the developed preterm model for the prediction of PK behaviour in preterm patients is not intended to replace clinical studies, it can potentially help with deciding on first-time dosing in this population and study design in the absence of clinical data.

Clinical Pharmacokinetics of Triazoles in Pediatric Patients

Triazoles represent an important class of antifungal drugs in the prophylaxis and treatment of invasive fungal disease in pediatric patients. Understanding the pharmacokinetics of triazoles in children is crucial to providing optimal care for this vulnerable population. While the pharmacokinetics is extensively studied in adult populations, knowledge on pharmacokinetics of triazoles in children is limited. New data are still emerging despite drugs already going off patent. This review aims to provide readers with the most current knowledge on the pharmacokinetics of the triazoles: fluconazole, itraconazole, voriconazole, posaconazole, and isavuconazole. In addition, factors that have to be taken into account to select the optimal dose are summarized and knowledge gaps are identified that require further research. We hope it will provide clinicians guidance to optimally deploy these drugs in the setting of a life-threatening disease in pediatric patients.

Optimization of Fluconazole Dosing for the Prevention and Treatment of Invasive Candidiasis Based on the Pharmacokinetics of Fluconazole in Critically Ill Patients

The efficacy of fluconazole is related to the area under the plasma concentration-time curve (AUC) over the MIC of the microorganism. Physiological changes in critically ill patients may affect the exposure of fluconazole, and therefore dosing adjustments might be needed. The aim of this study was to evaluate variability in fluconazole drug concentration in intensive care unit (ICU) patients and to develop a pharmacokinetic model to support personalized fluconazole dosing. A prospective observational pharmacokinetic study was performed in critically ill patients receiving fluconazole either as prophylaxis or as treatment. The association between fluconazole exposure and patient variables was studied. Pharmacokinetic modeling was performed with a nonparametric adaptive grid (NPAG) algorithm using R package Pmetrics. Data from 33 patients were available for pharmacokinetic analysis. Patients on dialysis and solid organ transplant patients had a significantly lower exposure to fluconazole. The population was best described with a one-compartment model, where the mean volume of distribution was 51.52 liters (standard deviation [SD], 19.81) and the mean clearance was 0.767 liters/h (SD, 0.46). Creatinine clearance was tested as a potential covariate in the model, but was not included in the final population model. A significant positive correlation was found between the fluconazole exposure (AUC) and the trough concentration (C _min). Substantial variability in fluconazole plasma concentrations in critically ill adults was observed, where the majority of patients were underexposed. Fluconazole C _min therapeutic drug monitoring (TDM)-guided dosing can be used to optimize therapy in critically ill patients. (This study has been registered at ClinicalTrials.gov under identifier NCT02491151.).

Review of Fluconazole Treatment and Prophylaxis for Invasive Candidiasis in Neonates

Invasive candidiasis accounts for approximately 10% of nosocomial infections in preterm infants, with an incidence of 1% to 4% among neonatal intensive care unit (NICU) admissions and a mortality as high as 20% to 30%. These outcomes warrant improved treatment and prevention strategies for infants at highest risk. The Infectious Diseases Society of America provides guidelines on antifungal medications for the prophylaxis and treatment of candidiasis in NICUs; however, there are still variations in practice on the use of fluconazole for prophylaxis and treatment of invasive candidiasis. This review provides specific information regarding fluconazole activity, pharmacokinetics, and a literature evaluation of dosing strategies and comparisons to other treatments in the neonatal population.

A meta-analysis of fluconazole for the prevention of invasive fungal infection in preterm infants

OBJECTIVE

The present aimed to evaluate the efficacy and safety of fluconazole for prophylactic use in preterm infants with very low birth weight (VLBW) by using an evidence-based methodology.

METHODS

A computerized literature search was conducted in PubMed, the Cochrane Database of Systematic Reviews, MEDLINE, EMBASE, the ISI Web of Knowledge databases, the Chinese Biomedical (CBM) database, China National Knowledge Infrastructure, the WanFang database, and the VIP Chinese science and technology journal database to find all the randomized controlled trials conducted between January 2000 and December 2019 that studied the prevention of invasive fungal infection (IFI) by fluconazole in preterm infants with VLBW. A meta-analysis was conducted using the RevMan 5.3 and GRADEprofiler 3.2.2 software.

RESULTS

A total of 14 studies (including 1,930 preterm infants with VLBW) were included. The meta-analysis found that the prophylactic use of fluconazole significantly reduced the incidence of IFI (RR = 0.39; 95% CI: 0.24-0.64, P < 0.05), overall mortality (RR = 0.77; 95% CI: 0.61-0.97, P < 0.05), and fungal colonization rate (RR = 0.32; 95% CI: 0.25-0.41, P < 0.05) in preterm infants with VLBW. There was no significant effect on some common complications and neurological development in preterm infants. The application of fluconazole would not lead to the development of fungal resistance in the short term and would have no significant adverse effects.

CONCLUSION

The prophylactic use of fluconazole significantly reduced the incidence of IFI, overall mortality, and fungal colonization in preterm infants; however, the impact of prophylactic use of fluconazole on preterm infants needs to be evaluated in a large number of clinical studies because of the limited data.

Population pharmacokinetic study of caffeine citrate in Chinese premature infants with apnea

WHAT IS KNOWN AND OBJECTIVES

Caffeine citrate is a commonly used methylxanthine for pharmacologic treatment of apnea of prematurity. The aim of this study was to develop and verify a population pharmacokinetic (PPK) model, which can provide a reference for individualized caffeine citrate treatment of apnea in Chinese premature infants.

METHODS

A total of 88 serum concentration measurements from 46 preterm patients (median gestational age 29 weeks) were retrospectively collected and the relevant clinical data of patients were recorded. The PPK analysis was performed by non-linear mixed-effect modelling method using NONMEM. Allometric scaling was applied in the PPK analysis, and the final model was evaluated by graphic and statistical methods, including goodness-of-fit plots, normalized prediction distribution errors plots and bootstrap procedures.

RESULTS

A one-compartment model with first-order elimination was successfully fitted to the data. The typical scaled values for the parameters clearance and volume of distribution (V) were 0.268 L/h and 109 L per 70 kg, respectively. The weight at the time of blood collection (CW) and post-natal age were identified as important predictors for pharmacokinetic parameters of caffeine. The evaluation process showed good stability and predictability of the final PPK model.

WHAT IS NEW AND CONCLUSION

This is a complete PPK study of caffeine citrate in Chinese premature infants with apnea, which complements caffeine pharmacokinetic data of the premature from China. A final PPK model was developed which may serve as a beneficial tool for the use of caffeine citrate in the treatment of apnea in Chinese preterm infants.

A sensitive method for analyzing fluconazole in extremely small volumes of neonatal serum

BACKGROUND

The need for a large volume of serum sample significantly reduces the feasibility of neonatal pharmacokinetic studies in daily practice, which must often rely on scavenged or opportunistic sampling. This problem is most apparent in preterm newborns, where ethical and practical considerations prohibit the collection of large sample volumes. Most of the fluconazole analysis assays published thus far required a minimum serum sample of 50 to 100 μL for a single assay. The purpose of the present study was to develop and validate a sensitive method requiring a smaller sample volume (10 μL) to satisfy clinically relevant research requirements.

METHODS

Following simple protein precipitation and centrifugation, the filtrated supernatant was injected into a liquid chromatography system and separated with a C18 reverse-phase column. Fluconazole and the internal standard (IS, fluconazole-d4) were detected and quantified using tandem mass spectrometry. The method was validated with reference to the Food and Drug Administration's Guidance for Industry. Accuracy and precision were evaluated at six quality control concentration levels (ranging from 0.01 to 100 μg/mL).

RESULTS

Investigated calibration curves were linear in the 0.01-100 μg/mL range. Intra- and inter-day accuracy (- 7.7 to 7.4%) and precision (0.3 to 6.0%) were below 15%. The calculated limit of detection and the lower limit of quantification (LLOQ) was 0.0019 μg/mL and 0.0031 μg/mL, respectively. Fluconazole in the prepared samples was stable for at least 4 months at - 20 °C and - 80 °C. This method was applied to analyze 234 serum samples from ten neonates who received fosfluconazole, a water-soluble phosphate prodrug of fluconazole which converts to fluconazole in the body, as part of a pharmacokinetic study using daily scavenged laboratory samples. The median (range) concentration up to 72 h after fosfluconazole administration was 2.9 (0.02 to 26.8 μg/mL) μg/mL, which was within the range of the calibration curve.

CONCLUSION

Fluconazole was able to be detected in an extremely small volume (10 μL) of serum from neonates receiving fosfluconazole. The method presented here can be used to quantify fluconazole concentrations for pharmacokinetic studies of the neonatal population by using scavenged samples.

Fluconazole Prophylaxis of Candida Infections in Preterm Neonates

Infections belong to the most serious health problems in neonates. Invasive candidiases are one of the leading causes of mortality and morbidity in Neonatal intensive care units (NICUs). A more cautious approach is adequate when dealing with fungal infections in premature neonates. Sometimes it is necessary to cure an infection at the very beginning just before manifestation of clinical symptoms. Neonatal colonization due to Candida albicans or non-albicans Candidae predisposes to invasive candidiasis. Pregnancies complicated by preterm delivery should be considered for screening and treatment of maternal Candida colonization to decrease the occurrence of neonatal fungal colonization and its consequences. It is important to prevent infection to spread among patients and avoid complications. Prophylaxis in neonates must be safe and effective. Most authors prefer selective prophylaxis. Fluconazole is the drug of choice for prophylaxis in extremely low birth weight (ELBW) neonates. The prophylaxis is beneficial especially in NICUs with high rates of invasive candidiases. The authors describe benefits and trends in prophylaxis. They also summarize evidence on timing, dosing, and effect of fluconazole prophylaxis.

Choosing the Right Antifungal Agent in ICU Patients

Fungi are responsible for around 20% of microbiologically documented infections in intensive care units (ICU). In the last decade, the incidence of invasive fungal infections (IFI), including candidemia, has increased steadily because of increased numbers of both immunocompromised and ICU patients. To improve the outcomes of patients with IFI, intensivists need to be aware of the inherent challenges. This narrative review summarizes the features of routinely used treatments directed against IFI in non-neutropenic ICU patients, which include three classes of antifungals: polyenes, azoles, and echinocandins. ICU patients’ pathophysiological changes are responsible for deep changes in the pharmacokinetics of antifungals. Moreover, drug interactions affect the response to antifungal treatments. Consequently, appropriate antifungal dosage is a challenge under these special conditions. Dosages should be based on renal and liver function, and serum concentrations should be monitored. This review summarizes recent guidelines, focusing on bedside management.

Population Pharmacokinetic Study of Prophylactic Fluconazole in Preterm Infants for Prevention of Invasive Candidiasis

Fluconazole is an antifungal agent with reported evidence for its prophylactic effect against systemic fungal infection in preterm infants. The aim of this study was to build a population pharmacokinetic model to evaluate the pharmacokinetic characteristics of intravenous and oral fluconazole in preterm infants with the current prophylactic fluconazole dosing regimen. A pharmacokinetic model was developed using 301 fluconazole concentrations from 75 preterm infants with a baseline body weight (WT) ranging from 0.5 to 1.5 kg and an estimated glomerular filtration rate (eGFR) ranging from 12.9 to 58.5 ml/min/1.73 m² Eligible infants received an intravenous or oral dose of 3 mg/kg of body weight of fluconazole, twice weekly with a ≥72-h dose interval, for 4 weeks. The model was qualified with basic goodness-of-fit diagnostics, visual predictive checks, and bootstrapping. The fluconazole pharmacokinetics was well described with a one-compartment linear model with a proportional residual error. The population clearance (CL) and volume of distribution (V) were derived as 0.0197 × (WT/1.00)^0.746 × (eGFR/25.0)^0.463 × exp(η) and 1.04 × WT × exp(η), respectively. Such covariate analyses augment the awareness of the need for personalized dosing in preterm infants. (This study has been registered at ClinicalTrials.gov under identifier NCT01683760).

Physiologically-Based Pharmacokinetic Modeling of Fluconazole Using Plasma and Cerebrospinal Fluid Samples From Preterm and Term Infants

Fluconazole is used to treat hematogenous Candida meningoencephalitis in preterm and term infants. To characterize plasma and central nervous system exposure, an adult fluconazole physiologically‐based pharmacokinetic (PBPK) model was scaled to infants, accounting for age dependencies in glomerular filtration and metabolism. The model was optimized using 760 plasma samples from 166 infants (median postmenstrual age (range) 28 weeks (24–50)) and 27 cerebrospinal fluid (CSF) samples from 22 infants (postmenstrual age 28 weeks (24–33)). Simulations evaluated achievement of the surrogate efficacy target of area under the unbound concentration‐time curve ≥ 400 mg • hour/L over the dosing interval in plasma and CSF using dosing guidelines. Average fold error of predicted concentrations was 0.73 and 1.14 for plasma and CSF, respectively. Target attainment in plasma and CSF was reached faster after incorporating a loading dose of 25 mg/kg. PBPK modeling can be useful in exploring CNS kinetics of drugs in children.

Antifungal Drugs for Invasive Candida Infections (ICI) in Neonates: Future Perspectives

Fungal infections may complicate the neonatal clinical course, and the spectrum of therapies for their treatment in the perinatal period is limited. Polyenes, Azoles and Echinocandins represent the three classes of antifungal drugs commonly used in the neonatal period. The present review provides an overview about the most recent therapeutic strategies for the treatment of fungal infections in neonates.

Effect of fluconazole prophylaxis on Candida fluconazole susceptibility in premature infants

OBJECTIVES

Extremely premature infants are at high risk of developing invasive candidiasis; fluconazole prophylaxis is safe and effective for reducing invasive candidiasis in this population but further study is needed. We sought to better understand the effect of prophylactic fluconazole on a selection of fluconazole-resistant Candida species.

METHODS

We evaluated the susceptibility to fluconazole of Candida isolates from premature infants (<750 g birth weight) enrolled in a multicentre, randomized, placebo-controlled trial of fluconazole prophylaxis. Candida species were isolated through surveillance cultures at baseline (study day 0-7), period 1 (study day 8-28) and period 2 (study day 29-49). Fluconazole MICs were determined for all Candida isolates.

RESULTS

Three hundred and sixty-one infants received fluconazole (n = 188) or placebo (n = 173). After the baseline period, Candida colonization was significantly lower in the fluconazole group compared with placebo during periods 1 (5% versus 27%; P < 0.001) and 2 (3% versus 27%; P < 0.001). After the baseline period, two infants (1%) were colonized with at least one fluconazole-resistant Candida in each group. Median fluconazole MIC was similar in both treatment groups at baseline and period 1. However, in period 2, median MIC was higher in the fluconazole group compared with placebo (1.00 versus 0.50 mg/L, P = 0.01). There was no emergence of resistance observed and no patients developed invasive candidiasis with a resistant Candida isolate.

CONCLUSIONS

Fluconazole prophylaxis decreased Candida albicans and 'non-albicans' Candida colonization and was associated with a slightly higher fluconazole MIC for colonizing Candida isolates.

External Evaluation of Two Fluconazole Infant Population Pharmacokinetic Models

Fluconazole is an antifungal agent used for the treatment of invasive candidiasis, a leading cause of morbidity and mortality in premature infants. Population pharmacokinetic (PK) models of fluconazole in infants have been previously published by Wade et al. (Antimicrob Agents Chemother 52:4043-4049, 2008, https://doi.org/10.1128/AAC.00569-08) and Momper et al. (Antimicrob Agents Chemother 60:5539-5545, 2016, https://doi.org/10.1128/AAC.00963-16). Here we report the results of the first external evaluation of the predictive performance of both models. We used patient-level data from both studies to externally evaluate both PK models. The predictive performance of each model was evaluated using the model prediction error (PE), mean prediction error (MPE), mean absolute prediction error (MAPE), prediction-corrected visual predictive check (pcVPC), and normalized prediction distribution errors (NPDE). The values of the parameters of each model were reestimated using both the external and merged data sets. When evaluated with the external data set, the model proposed by Wade et al. showed lower median PE, MPE, and MAPE (0.429 μg/ml, 41.9%, and 57.6%, respectively) than the model proposed by Momper et al. (2.45 μg/ml, 188%, and 195%, respectively). The values of the majority of reestimated parameters were within 20% of their respective original parameter values for all model evaluations. Our analysis determined that though both models are robust, the model proposed by Wade et al. had greater accuracy and precision than the model proposed by Momper et al., likely because it was derived from a patient population with a wider age range. This study highlights the importance of the external evaluation of infant population PK models.

Pharmacokinetics of antifungal drugs: practical implications for optimized treatment of patients

Introduction

Because of the high mortality of invasive fungal infections (IFIs), appropriate exposure to antifungals appears to be crucial for therapeutic efficacy and safety.

Materials and methods

This review summarises published pharmacokinetic data on systemically administered antifungals focusing on co-morbidities, target-site penetration, and combination antifungal therapy.

Conclusions and discussion

Amphotericin B is eliminated unchanged via urine and faeces. Flucytosine and fluconazole display low protein binding and are eliminated by the kidney. Itraconazole, voriconazole, posaconazole and isavuconazole are metabolised in the liver. Azoles are substrates and inhibitors of cytochrome P450 (CYP) isoenzymes and are therefore involved in numerous drug–drug interactions. Anidulafungin is spontaneously degraded in the plasma. Caspofungin and micafungin undergo enzymatic metabolism in the liver, which is independent of CYP. Although several drug–drug interactions occur during caspofungin and micafungin treatment, echinocandins display a lower potential for drug–drug interactions. Flucytosine and azoles penetrate into most of relevant tissues. Amphotericin B accumulates in the liver and in the spleen. Its concentrations in lung and kidney are intermediate and relatively low myocardium and brain. Tissue distribution of echinocandins is similar to that of amphotericin. Combination antifungal therapy is established for cryptococcosis but controversial in other IFIs such as invasive aspergillosis and mucormycosis.

Fluconazole Doses Used for Prophylaxis of Invasive Fungal Infection in Neonatal Intensive Care Units: A Network Meta-Analysis

OBJECTIVES

To evaluate the safety and efficacy of different doses of fluconazole used for invasive prophylaxis of fungal infection in neonates.

STUDY DESIGN

A systematic search was conducted with PubMed, Scopus, and Web of Science. A manual search was performed as well. Only randomized controlled trials of neonates in a neonatal intensive care unit (NICU) who received fluconazole prophylaxis for invasive fungal infection, regardless of the dose or therapeutic regimen, were included in this review. Data on baseline characteristics, outcomes incidence of proven invasive Candida infection, overall mortality, and invasive Candida infection-related mortality were extracted.

RESULTS

Eleven studies were included in the review, with fluconazole doses of 3, 4, or 6?mg/kg. When the incidence of invasive Candida and invasive Candida-related mortality were considered as outcomes, the 3 and 6?mg/kg fluconazole doses were found to be statistically superior to placebo (OR, 5.48 [95% credible interval, 1.81-18.94] and 2.63 [1.18-7.02], respectively, and 15.32 [1.54-54.31] and 9.14 [1.26-142.7], respectively), but data for the 3 doses were not statistically significantly different.

CONCLUSIONS

Use of the lowest fluconazole dose (3?mg/kg) should be recommended for Candida prophylaxis in neonates, given that increasing the fluconazole dose is not associated with higher efficacy and has greater potential for toxicity and increased cost.