Fluconazole population pharmacokinetics and dosing for prevention and treatment of invasive Candidiasis in children supported with extracorporeal membrane oxygenation

A narrative review on antimicrobial dosing in adult critically ill patients on extracorporeal membrane oxygenation

The optimal dosing strategy of antimicrobial agents in critically ill patients receiving extracorporeal membrane oxygenation (ECMO) is unknown. We conducted comprehensive review of existing literature on effect of ECMO on pharmacokinetics and pharmacodynamics of antimicrobials, including antibacterials, antifungals, and antivirals that are commonly used in critically ill patients. We aim to provide practical guidance to clinicians on empiric dosing strategy for these patients. Finally, we discuss importance of therapeutic drug monitoring, limitations of current literature, and future research directions.

The impact of extracorporeal support on antimicrobial pharmacokinetics in critically ill neonatal and paediatric patients: A systematic review

OBJECTIVES

Infections represent a major risk for critically ill neonatal and paediatric patients requiring extracorporeal life-saving support such as extracorporeal membrane oxygenation (ECMO) and/or continuous renal replacement therapies (CRRT). Patient outcomes rely on achieving target antimicrobial concentrations. In critically ill adults on extracorporeal support, suboptimal antimicrobial concentrations have been shown to be common. Our objective was to systematically review antimicrobial pharmacokinetic studies in critically ill term neonatal and paediatric patients receiving ECMO and/or CRRT and compare them to similar cohorts of patients not receiving ECMO or CRRT.

METHODS

Studies published between 1990 and 2022 were identified through systematic searches in PUBMED, Embase, Web of Science, Medline, Google Scholar and CINAHL. Studies were included which provided antimicrobial pharmacokinetic parameters (volume of distribution and clearance) in the neonatal and paediatric patients receiving ECMO and/or CRRT. Studies were excluded if no antimicrobial pharmacokinetic parameters were described or could be calculated.

RESULTS

Forty-four pharmacokinetic studies were identified describing 737 patients, with neonatal patients recruited in 70% of the ECMO studies and <1% of the CRRT studies. Of all the studies, 50% were case reports or case series. The pharmacokinetics were altered for gentamicin, daptomycin, ceftolozane, micafungin, voriconazole, cefepime, fluconazole, piperacillin, and vancomycin, although considerable patient variability was described.

CONCLUSION

Significant gaps remain in our understanding of the pharmacokinetic alterations in neonatal and paediatric patients receiving ECMO and CRRT support.

The impact of extracorporeal membrane oxygenation on antifungal pharmacokinetics: A systematic review

BACKGROUND AND OBJECTIVE

The use of extracorporeal membrane oxygenation (ECMO) as a cardiocirculatory or respiratory support has tremendously increased in critically ill patients. In the setting of ECMO support, invasive fungal infections are a severe cause of morbidity and mortality. This vulnerable population is at risk of suboptimal antifungal exposure due to an increased volume of distribution (Vd), drug sequestration and decreased clearance. Here, we aimed to summarize ex-vivo and clinical studies on the potential impact of ECMO on the pharmacokinetics (PK) of antifungal agents and dosing requirements.

METHODS

A systematic search of the literature within electronic databases PubMed and EMBASE was conducted from database inception to 30 April 2023. Inclusion criteria were as follows: critically ill patients receiving ECMO regardless of age and reporting at least one PK parameter.

RESULTS

Thirty-six studies met inclusion criteria, including seven ex-vivo experiments and 29 clinical studies evaluating three classes of antifungals: polyenes, triazoles and echinocandins. Based on the available ex-vivo PK data, we found a significant sequestration of highly lipophilic and protein-bound antifungals within the ECMO circuit such as voriconazole, posaconazole and micafungin but the PK of several antifungals remains to be addressed such as amphotericin B, isavuconazole and anidulafungin. Most clinical studies have shown increased Vd of some antifungals like fluconazole and micafungin, particularly in the pediatric population. Conflicting data exist about caspofungin exposure.

CONCLUSIONS

The available literature on the antifungal PK changes in ECMO setting is scarce. Whenever possible, therapeutic drug monitoring is highly advised to personalize antifungal therapy.

Population pharmacokinetics of fluconazole in critically ill patients receiving extracorporeal membrane oxygenation and continuous renal replacement therapy: an ASAP ECMO study

This multicenter study describes the population pharmacokinetics (PK) of fluconazole in critically ill patients receiving concomitant extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT) and includes an evaluation of different fluconazole dosing regimens for achievement of target exposure associated with maximal efficacy. Serial blood samples were obtained from critically ill patients on ECMO and CRRT receiving fluconazole. Total fluconazole concentrations were measured in plasma using a validated chromatographic assay. A population PK model was developed and Monte Carlo dosing simulations were performed using Pmetrics in R. The probability of target attainment (PTA) of various dosing regimens to achieve fluconazole area under the curve to minimal inhibitory concentration ratio (AUC0-24/MIC) >100 was estimated. Eight critically ill patients receiving concomitant ECMO and CRRT were included. A two-compartment model including total body weight as a covariate on clearance adequately described the data. The mean (±standard deviation, SD) clearance and volume of distribution were 2.87 ± 0.63 L/h and 15.90 ± 13.29 L, respectively. Dosing simulations showed that current guidelines (initial loading dose of 12 mg/kg then 6 mg/kg q24h) achieved >90% of PTA for a MIC up to 1 mg/L. None of the tested dosing regimens achieved 90% of PTA for MIC above 2 mg/L. Current fluconazole dosing regimen guidelines achieved >90% PTA only for Candida species with MIC <1 mg/L and thus should be only used for Candida-documented infections in critically ill patients receiving concomitant ECMO and CRRT. Total body weight should be considered for fluconazole dose.

Antifungal Dosing in Critically Ill Patients on Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is an established advanced life support system, providing temporary cardiac and/or respiratory support in critically ill patients. Fungal infections are associated with increased mortality in patients on ECMO. Antifungal drug dosing for critically ill patients is highly challenging because of altered pharmacokinetics (PK). PK changes during critical illness; in particular, the drug volume of distribution (Vd) and clearance can be exacerbated by ECMO. This article discusses the available literature to inform adequate dosing of antifungals in this patient population. The number of antifungal PK studies in critically ill patients on ECMO is growing; currently available literature consists of case reports and studies with small sample sizes providing inconsistent findings, with scant or no data for some antifungals. Current data are insufficient to provide definitive empirical drug dosing guidance and use of dosing strategies derived from critically patients not on ECMO is reasonable. However, due to high PK variability, therapeutic drug monitoring should be considered where available in critically ill patients receiving ECMO to prevent subtherapeutic or toxic antifungal exposures.

Population Pharmacokinetics of Piperacillin/Tazobactam Across the Adult Lifespan

BACKGROUND AND OBJECTIVE

Piperacillin/tazobactam is one of the most frequently used antimicrobials in older adults. Using an opportunistic study design, we evaluated the pharmacokinetics of piperacillin/tazobactam as a probe drug to evaluate changes in antibacterial drug exposure and dosing requirements, including in older adults.

METHODS

A total of 121 adult patients were included. The population pharmacokinetic models that best characterized the observed plasma concentrations of piperacillin and tazobactam were one-compartment structural models with zero-order input and linear elimination.

RESULTS

Among all potential covariates, estimated creatinine clearance had the most substantial impact on the elimination clearance for both piperacillin and tazobactam. After accounting for renal function and body size, there was no remaining impact of frailty on the pharmacokinetics of piperacillin and tazobactam. Monte Carlo simulations indicated that renal function had a greater impact on the therapeutic target attainment than age, although these covariates were highly correlated. Frailty, using the Canadian Study of Health and Aging Clinical Frailty Scale, was assessed in 60 patients who were ≥ 65 years of age.

CONCLUSIONS

The simulations suggested that adults ≤ 50 years of age infected with organisms with higher minimum inhibitory concentrations may benefit from continuous piperacillin/tazobactam infusions (12 g/day of piperacillin component) or extended infusions of 4 g every 8 hours. However, for a target of 50% fT + minimum inhibitory concentration, dosing based on renal function is generally preferable to dosing by age, and simulations suggested that patients with creatinine clearance ≥ 120 mL/min may benefit from infusions of 4 g every 8 hours for organisms with higher minimum inhibitory concentrations.

Population pharmacokinetics in critically ill neonates and infants undergoing extracorporeal membrane oxygenation: a literature review

Extracorporeal membrane oxygenation (ECMO) increases circulating blood volume, causes capillary leak and temporarily alters kidney function. Consequently, pharmacokinetics (PK) can be affected. When applied to neonates and infants, additional dose adjustments are a major concern, as the volume of distribution (Vd) is already generally greater for water-soluble drugs and the clearance (Cl) of drugs eliminated by glomerular filtration is reduced. A systematic search was performed on MEDLINE (1994-2022) using a combination of the following search terms: "pharmacokinetics", "extracorporeal membrane oxygenation" and "infant, newborn" using Medical Subject Headings search strategy. Nine out of 18 studies on 11 different drugs (vancomycin, meropenem, fluconazole, gentamicin, midazolam, phenobarbital, theophylline, clonidine, morphine, cefotaxime and cefepime) recommended dose increase/decrease by determining PK parameters. In other studies, it has been suggested to adjust the dose intervals. While the elimination half-life (t_1/2) and Vd mostly increased for all drugs, the Cl of the drugs has been shown to have variability except for midazolam and morphine. There are a limited number of population PK studies in neonates and infants undergoing ECMO circuits. Despite some divergences, the general pattern suggests an increase in Vd and t_1/2, an increased, stable or decreased Cl, and an increase in variability. Consequently, and if possible, therapeutic drug monitoring and target concentration intervention are strongly recommended to determine appropriate exposure and doses for neonates and infants undergoing ECMO support.

A Narrative Review of the Impact of Extracorporeal Membrane Oxygenation on the Pharmacokinetics and Pharmacodynamics of Critical Care Therapies

Objective:

Extracorporeal membrane oxygenation (ECMO) utilization is increasing on a global scale, and despite technological advances, minimal standardized approaches to pharmacotherapeutic management exist. This objective was to create a comprehensive review for medication dosing in ECMO based on the most current evidence.

Data Sources:

A literature search of PubMed was performed for all pertinent articles prior to 2022. The following search terms were utilized: ECMO, pharmacokinetics, pharmacodynamics, sedation, analgesia, antiepileptic, anticoagulation, antimicrobial, antifungal, nutrition. Retrospective cohort studies, case-control studies, case series, case reports, and ex vivo investigations were reviewed.

Study Selection and Data Extraction:

PubMed (1975 through July 2022) was the database used in the literature search. Non-English studies were excluded. Search terms included both drug class categories, specific drug names, ECMO, and pharmacokinetics.

Data Synthesis:

Medications with high protein binding (>70%) and high lipophilicity (logP > 2) are associated with circuit sequestration and the potential need for dose adjustment. Volume of distribution changes with ECMO may also impact dosing requirements of common critical care medications. Lighter sedation targets and analgosedation may help reduce sedative and analgesia requirements, whereas higher antiepileptic dosing is recommended. Vancomycin is minimally affected by the ECMO circuit and recommendations for dosing in critically ill adults are reasonable. Anticoagulation remains challenging as optimal aPTT goals have not been established.

Relevance to Patient Care and Clinical Practice:

This review describes the anticipated impacts of ECMO circuitry on sedatives, analgesics, anticoagulation, antiepileptics, antimicrobials, antifungals, and nutrition support and provides recommendations for drug therapy management.

Conclusions:

Medication pharmacokinetic/pharmacodynamic parameters should be considered when determining the potential impact of the ECMO circuit on attainment of therapeutic effect and target serum drug concentrations, and should guide therapy choices and/or dose adjustments when data are not available.

Experimental models for pharmacokinetic and pharmacodynamic studies of antifungals used in cryptococcosis treatment

Studies on cryptococcosis in the mammal animal model have demonstrated the occurrence of central nervous system infection and similarities in fungal pathogenicity with clinical and immunological features of the human infection. Although there is still a lack of studies involving pharmacokinetics (PK) and pharmacodynamics (PD) in animal models of cryptococcosis in the literature, these experimental models are useful for understanding this mycosis and antifungal effectiveness in improving the therapeutic schemes. The scope of this review is to describe and discuss the main mammal animal models for PK and PD studies of antifungals used in cryptococcosis treatment. Alternative models and computational methods are also addressed. All approaches for PK/PD studies are relevant to investigating drug-infection interaction and improving cryptococcosis therapy.

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.

Pharmacokinetics of Commonly Used Medications in Children Receiving Continuous Renal Replacement Therapy: A Systematic Review of Current Literature

BACKGROUND AND OBJECTIVE

The use of continuous renal replacement therapy (CRRT) for renal support has increased substantially in critically ill children compared with intermittent modalities owing to its preferential effects on hemodynamic stability. With the expanding role of CRRT, the quantification of extracorporeal clearance and the effect on primary pharmacokinetic parameters is of the utmost importance. Within this review, we aimed to summarize the current state of the literature and compare published pharmacokinetic analyses of commonly used medications in children receiving CRRT to those who are not.

METHODS

A systematic search of the literature within electronic databases PubMed, EMBASE, Cochrane Library, and Web of Science was conducted. Published studies that were included contained relevant information on the use of commonly administered medications to children, from neonates to adolescents, receiving CRRT. Pharmacokinetic parameters that were analyzed included volume of distribution, total clearance, extracorporeal clearance, area under the curve, and elimination half-life. Information regarding CRRT circuit, flow rates, and membrane components was analyzed to investigate differences in pharmacokinetics between each modality.

RESULTS

Forty-five studies met the final inclusion criteria within this systematic review, totaling 833 pediatric patients, with 586 receiving CRRT. Antimicrobials were the most common pharmacological class represented within the literature, representing 81% (35/43) of studies analyzed. Children receiving CRRT largely had similar volume of distribution and total clearance to critically ill children not receiving CRRT, suggesting reno-protective dose adjustments may lead to subtherapeutic dosing regimens in these patients. Overall, there was a tendency for hydrophilic agents, with a low protein binding to undergo elevated total clearance in these children. However, results should be interpreted with caution because of the large variability amongst patient populations and heterogeneity with CRRT modalities, flow rates, and use of extracorporeal membrane oxygenation within studies. This review was able to identify that variation in solute removal, or CRRT modalities, properties (i.e., flow rates), and membrane composition, may have differing effects on the pharmacokinetics of commonly administered medications.

CONCLUSIONS

The current state of the literature regarding medications administered to children receiving CRRT largely focuses on antimicrobials. Significant gaps remain with other commonly used medications such as sedatives and analgesics. Overall reporting of patient clinical characteristics, CRRT settings, and circuit composition was poor, with only 10% of articles including all relevant information to assess the impact of CRRT on total clearance. Changes in pharmacokinetics because of CRRT often required higher than labeled doses, suggesting renally adjusted or reno-protective doses may lead to subtherapeutic dosing regimens. A thorough understanding of the interplay between patient, drug, and CRRT-circuit factors are required to ensure adequate delivery of dosing regimens to this vulnerable population.

Pharmacokinetics of fluconazole and ganciclovir as combination antimicrobial chemotherapy on ECMO: a case report

Extracorporeal membrane oxygenation (ECMO) can affect antimicrobial pharmacokinetics. This case report describes a 33-year-old male with newly diagnosed acquired immunodeficiency syndrome presenting in acute severe type 1 respiratory failure. On investigation, the patient had positive cultures for Candida albicans from respiratory specimens and high blood cytomegalovirus titres, and required venovenous ECMO therapy for refractory respiratory failure. Intravenous fluconazole (6 mg/kg, 24-h) and ganciclovir (5 mg/kg, 12-h) was commenced. Pre-oxygenator, post-oxygenator and arterial blood samples were collected after antibiotic administration, and were analysed for total fluconazole and ganciclovir concentrations. Although there was a 40% increase in the volume of distribution for fluconazole relative to healthy volunteers, the pharmacodynamic targets for prophylaxis were still met. The area under the curve exposure of ganciclovir (50.78 mg•h/L) achieved target thresholds. The ECMO circuit had no appreciable effect on achievement of therapeutic exposures of fluconazole and ganciclovir.

[Effect of extracorporeal membrane oxygenation on pharmacokinetics of antimicrobial drugs: recent progress and recommendations]

Extracorporeal membrane oxygenation (ECMO) is an effective means to provide life support for patients with severe respiratory or heart failure. Existing studies have shown that ECMO may affect the metabolic process of some drugs by drug adsorption, increasing the apparent distribution volume and changing the clearance rate of the drugs. This review summarizes the recent progress in the studies of the effect of ECMO on the pharmacokinetics of antibacterial and antifungal drugs. For the antibacterial drugs, it is recommended that the dose of teicoplanin, imipenem, and linezolid should be increased during ECMO support, while the dose of azithromycin, ciprofloxacin, and tigecycline should not be modified for the time being. Currently studies on pharmacokinetic changes of antifungal drugs during ECMO support remain limited. Voriconazole can be absorbed substantially by ECMO due to its high lipophilicity, and higher doses are therefore recommended. The dose of micafungin also needs to be increased in children undergoing ECMO. However, current evidence concerning the dose of caspofungin and fluconazole are limited, and it is not clear whether the routine dose should be adjusted during ECMO support.

Extracorporeal membrane oxygenation in critically ill neonatal and pediatric patients with acute respiratory failure: a guide for the clinician

Intro: Extracorporeal membrane oxygenation for neonatal and pediatric respiratory failure continues to demonstrate improving outcomes, largely due to advances in technology along with refined management strategies despite mounting patient acuity and complexity. Successful use of ECMO requires thoughtful initiation and candidacy strategies, along with reducing the risk of ventilator induced lung injury and the progression to multiorgan failure.Areas Covered: This review describes current ECMO management strategies for neonatal and pediatric patients with acute refractory respiratory failure and summarizes relevant published literature. ECMO initiation and candidacy, along with ventilator and sedation management, are highlighted. Additionally, rapidly expanding areas of interest such as anticoagulation strategies, transfusion thresholds, rehabilitation on ECMO, and drug pharmacokinetics are described.Expert Opinion: Over the last few decades, published studies supporting ECMO use for acute refractory respiratory failure, along with institutional experience, have resulted in increased utilization although more randomized-controlled trials are needed. Future research should focus on filling the knowledge gaps that remain regarding anticoagulation, transfusion thresholds, ventilator strategies, sedation, and approaches to rehabilitation to subsequently implement into clinical practice. Additionally, efforts should focus on well-designed trials, including population pharmacokinetic studies, to develop dosing recommendations.

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.).

Invasive candidiasis in critical care: challenges and future directions

Invasive candidiasis is the most common critical care-associated fungal infection with a crude mortality of ~ 40-55%. Important factors contributing to risk of invasive candidiasis in ICU include use of broad-spectrum antimicrobials, immunosuppressive drugs, and total parenteral nutrition alongside iatrogenic interventions which breach natural barriers to infection [vascular catheters, renal replacement therapy, extracorporeal membrane oxygenation (ECMO), surgery]. This review discusses three key challenges in this field. The first is the shift in Candida epidemiology across the globe to more resistant non-albicans species, in particular, the emergence of multi-resistant Candida glabrata and Candida auris, which pose significant treatment and infection control challenges in critical care. The second challenge lies in the timely and appropriate initiation and discontinuation of antifungal therapy. Early antifungal strategies (prophylaxis, empirical and pre-emptive) using tools such as the Candida colonisation index, clinical prediction rules and fungal non-culture-based tests have been developed: we review the evidence on implementation of these tools in critical care to aid clinical decision-making around the prescribing and cessation of antifungal therapy. The third challenge is selection of the most appropriate antifungal to use in critical care patients. While guidelines exist to aid choice, this heterogenous and complex patient group require a more tailored approach, particularly in cases of acute kidney injury, liver impairment and for patients supported by extracorporeal membrane oxygenation. We highlight key research priorities to overcome these challenges in the future.

Pharmacokinetics Alterations in Critically Ill Pediatric Patients on Extracorporeal Membrane Oxygenation: A Systematic Review

Objectives: This study aimed to identify alterations in pharmacokinetics in children on extracorporeal membrane oxygenation (ECMO), identify knowledge gaps, and inform future pharmacology studies. Data Sources: We systematically searched the databases MEDLINE, CINAHL, and Embase from earliest publication until November 2018 using a controlled vocabulary and keywords related to "ECMO" and "pharmacokinetics," "pharmacology," "drug disposition," "dosing," and "pediatrics." Study Selection: Inclusion criteria were as follows: study population aged <18 years, supported on ECMO for any indications, received any medications while on ECMO, and reported pharmacokinetic data. Data Extraction: Clearance and/or volume of distribution values were extracted from included studies. Data Synthesis: Forty-one studies (total patients = 574) evaluating 23 drugs met the inclusion criteria. The most common drugs studied were antimicrobials (n = 13) and anticonvulsants (n = 3). Twenty-eight studies (68%) were conducted in children <1 year of age. Thirty-three studies (80%) were conducted without intra-study comparisons to non-ECMO controls. Increase in volume of distribution attributable to ECMO was demonstrated for nine (56%) drugs: cefotaxime, gentamicin, piperacillin/tazobactam, fluconazole, micafungin, levetiracetam, clonidine, midazolam, and sildenafil (range: 23-345% increase relative to non-ECMO controls), which may suggest the need for higher initial dosing. Decreased volume of distribution was reported for two drugs: acyclovir and ribavirin (50 and 69%, respectively). Decreased clearance was reported for gentamicin, ticarcillin/clavulanate, bumetanide, and ranitidine (range: 26-95% decrease relative to non-ECMO controls). Increased clearance was reported for caspofungin, micafungin, clonidine, midazolam, morphine, and sildenafil (range: 25-455% increase relative to non-ECMO controls). Conclusions: There were substantial pharmacokinetic alterations in 70% of drugs studied in children on ECMO. However, studies evaluating pharmacokinetic changes of many drug classes and those that allow direct comparisons between ECMO and non-ECMO patients are still lacking. Systematic evaluations of pharmacokinetic alterations of drugs on ECMO that incorporate multidrug opportunistic trials, physiologically based pharmacokinetic modeling, and other methods are necessary for definitive dose recommendations. Trial Registration Prospero Identifier: CRD42019114881.

Sequestration of Voriconazole and Vancomycin Into Contemporary Extracorporeal Membrane Oxygenation Circuits: An in vitro Study

Background: Bacterial and fungal infections are common and often contribute to death in patients undergoing extracorporeal membrane oxygenation (ECMO). Drug disposition is altered during ECMO, and adsorption in the circuit is an established causative factor. Vancomycin and voriconazole are widely used, despite the lack of evidence-based prescription guidelines. Objective: The objective of this study was to determine the extraction of voriconazole and vancomycin by the Xenios/Novalung ECMO circuits. Methods: We have set up nine closed-loop ECMO circuits, consisting of four different iLAActivve ^® kits for neonatal, pediatric, and adult support: three iLA-ActivveMiniLung ^® petite kits, two iLA-ActivveMiniLung ^® kits, two iLA-ActivveiLA ^® kits, and two iLA-Activve X-lung ^® kits. The circuits were primed with whole blood and maintained at physiologic conditions for 24 h. Voriconazole and vancomycin were injected as a single-bolus age-related dose into the circuits. Pre-membrane (P2) blood samples were obtained at baseline and after drug injection at 2, 10, 30, 180, 360 min, and 24 h. A control sample at 2 min was collected for spontaneous drug degradation testing at 24 h. Results: Seventy-two samples were analyzed in triplicate. The mean percentage of drug recovery at 24 h was 20% for voriconazole and 62% for vancomycin. Conclusions: The extraction of voriconazole and vancomycin by contemporary ECMO circuits is clinically relevant across all age-related circuit sizes and may result in reduced drug exposure in vivo.

Pharmacokinetics and Pharmacodynamics of Anti-infective Agents during Continuous Veno-venous Hemofiltration in Critically Ill Patients: Lessons Learned from an Ancillary Study of the IVOIRE Trial

Background

Hemofiltration rate, changes in blood and ultrafiltration flow, and discrepancies between the prescribed and administered doses strongly influence pharmacokinetics (PK) and pharmacodynamics (PD) of antimicrobial agents during continuous veno-venous hemofiltration (CVVH) in critically ill patients.

Methods

Ancillary data were from the prospective multicenter IVOIRE (hIgh VOlume in Intensive caRE) study. High volume (HV, 70 mL/kg/h) was at random compared with standard volume (SV, 35 mL/kg/h) CVVH in septic shock patients with acute kidney injury (AKI). PK/PD parameters for all antimicrobial agents used in each patient were studied during five days.

Results

Antimicrobial treatment met efficacy targets for both percentage of time above the minimal inhibitory concentration and inhibitory quotient. A significant correlation was observed between the ultrafiltration flow and total systemic clearance (Spearman test: P < 0.005) and between CVVH clearance and drug elimination half-life (Spearman test: P < 0.005). All agents were easily filtered. Mean sieving coefficient ranged from 38.7% to 96.7%. Mean elimination half-life of all agents was significantly shorter during HV-CVVH (from 1.29 to 28.54 h) than during SV-CVVH (from 1.51 to 33.85 h) (P < 0.05).

Conclusions

This study confirms that CVVH influences the PK/PD behavior of most antimicrobial agents. Antimicrobial elimination was directly correlated with convection rate. Current antimicrobial dose recommendations will expose patients to underdosing and increase the risk for treatment failure and development of resistance. Dose recommendations are proposed for some major antibiotic and antifungal treatments in patients receiving at least 25 mL/kg/h CVVH.

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.

Overview of antifungal dosing in invasive candidiasis

In the past, most antifungal therapy dosing recommendations for invasive candidiasis followed a 'one-size fits all' approach with recommendations for lowering maintenance dosages for some antifungals in the setting of renal or hepatic impairment. A growing body of pharmacokinetic/pharmacodynamic research, however now points to a widespread 'silent epidemic' of antifungal underdosing for invasive candidiasis, especially among critically ill patients or special populations who have altered volume of distribution, protein binding and drug clearance. In this review, we explore how current adult dosing recommendations for antifungal therapy in invasive candidiasis have evolved, and special populations where new approaches to dose optimization or therapeutic drug monitoring may be needed, especially in light of increasing antifungal resistance among Candida spp.

Clinical pharmacology considerations for children supported with ventricular assist devices

The ventricular assist device is being increasingly used as a "bridge-to-transplant" option in children with heart failure who have failed medical management. Care for this medically complex population must be optimised, including through concomitant pharmacotherapy. Pharmacokinetic/pharmacodynamic alterations affecting pharmacotherapy are increasingly discovered in children supported with extracorporeal membrane oxygenation, another form of mechanical circulatory support. Similarities between extracorporeal membrane oxygenation and ventricular assist devices support the hypothesis that similar alterations may exist in ventricular assist device-supported patients. We conducted a literature review to assess the current data available on pharmacokinetics/pharmacodynamics in children with ventricular assist devices. We found two adult and no paediatric pharmacokinetic/pharmacodynamic studies in ventricular assist device-supported patients. While mechanisms may be partially extrapolated from children supported with extracorporeal membrane oxygenation, dedicated investigation of the paediatric ventricular assist device population is crucial given the inherent differences between the two forms of mechanical circulatory support, and pathophysiology that is unique to these patients. Commonly used drugs such as anticoagulants and antibiotics have narrow therapeutic windows with devastating consequences if under-dosed or over-dosed. Clinical studies are urgently needed to improve outcomes and maximise the potential of ventricular assist devices in this vulnerable population.

Physiologically Based Pharmacokinetic Approach to Determine Dosing on Extracorporeal Life Support: Fluconazole in Children on ECMO

Extracorporeal life support (e.g., dialysis, extracorporeal membrane oxygenation (ECMO)) can affect drug disposition, placing patients at risk for therapeutic failure. In this population, dose selection to achieve safe and effective drug exposure is difficult. We developed a novel and flexible approach that uses physiologically based pharmacokinetic (PBPK) modeling to translate results from ECMO ex vivo experiments into bedside dosing recommendations. To determine fluconazole dosing in children on ECMO, we developed a PBPK model, which was validated using fluconazole pharmacokinetic (PK) data in adults and critically ill infants. Next, an ECMO compartment was added to the PBPK model and parameterized using data from a previously published ex vivo study. Simulations using the final ECMO PBPK model reasonably characterized observed PK data in infants on ECMO, and the model was used to derive dosing in children on ECMO across the pediatric age spectrum. This approach can be generalized to other forms of extracorporeal life support (ECLS), such as dialysis.

Drugs pharmacokinetics during veno-venous extracorporeal membrane oxygenation in pediatrics

Data evaluating pharmacokinetic/pharmacodynamic (PK/PD) aspect in the pediatric population are scarce especially regarding the pediatric intensive care unit. Dosing of frequently used drugs (sedatives, analgesics, antibiotics and cardiovascular drugs) are mainly based on non "pediatric intensive care unit (PICU)" patients, and sometimes are translated from adult patients. Among PICU patients, the most complex patients are the ones who are critically ill and are receiving mechanical circulatory/respiratory support for cardiac and/or respiratory failure. The use of extracorporeal membrane oxygenation is associated with major PK and PD changes, especially in neonates and children. The objective of this review is to assess the current literature for pediatric PK data in patients receiving extracorporeal membrane oxygenation (ECMO).

Pharmacokinetic changes of antibiotic, antiviral, antituberculosis and antifungal agents during extracorporeal membrane oxygenation in critically ill adult patients

WHAT IS KNOWN AND OBJECTIVE

Extracorporeal membrane oxygenation (ECMO) is a life-saving system used for critically ill patients with cardiac and/or respiratory failure. The pharmacokinetics (PK) of drugs can change in patients undergoing ECMO, which can result in therapeutic failure or drug toxicity requiring further management of drug complications. In this review, we discussed changes in the PK of antibiotic, antiviral, antituberculosis and antifungal agents administered to adult patients on ECMO. These drugs are crucial for managing infections, which commonly occur during ECMO.

METHODS

A literature search was conducted using the PubMed and EMBASE databases with the following keywords: "extracorporeal membrane oxygenation OR extracorporeal membrane oxygenations OR ECMO" and "PK OR pharmacokinetics OR pharmacokinetic*" and "anti infective* OR antibiotic* OR antiviral* OR antituberculosis OR antifungal*."

RESULTS AND DISCUSSION

Generally, the volume of distribution (Vd) increases and drug clearance (CL) and elimination decrease during ECMO. Highly significant changes in drug PK can occur by interactions with the ECMO device itself, drug characteristics, pathological changes and patient characteristics. This may affect the blood concentrations of drugs, which influence the success of therapy. The PK of vancomycin, piperacillin-tazobactam, meropenem, azithromycin, amikacin and caspofungin did not change significantly in adult patients receiving ECMO. However, there were significant changes in the PK of imipenem, oseltamivir, rifampicin and voriconazole. The trough concentrations of imipenem were highly variable; oseltamivir had a decreased CL and increased Vd, and rifampicin concentrations were below therapeutic levels, even when a higher-than-standard dose was used in patients treated with ECMO. Additionally, voriconazole exhibited high mean peak concentrations during ECMO.

WHAT IS NEW AND CONCLUSION

The impact of ECMO on PK varies among drugs in adult patients, and there is no consistent correlation between the effects observed in adult and infant studies. This review suggested that doses of imipenem, oseltamivir, rifampicin and voriconazole should be adjusted and therapeutic drug monitoring is needed when ECMO is used in adult patients. In the future, large PK trials in adults on ECMO are needed to provide optimal dosing guidelines. A PK/PD modelling approach will be useful for determining the precise impact of ECMO and other factors that contribute to PK changes for each drug. Finally, it is important to develop dosing guidelines based on PK/PD modelling studies that can be used in clinical practice.

Antifungal Extraction by the Extracorporeal Membrane Oxygenation Circuit

Invasive candidiasis is common and often fatal in patients supported with extracorporeal membrane oxygenation (ECMO), and treatment relies on optimal antifungal dosing. The ECMO circuit can extract drug and decrease drug exposure, placing the patient at risk of therapeutic failure. This ex vivo study determined the extraction of antifungal drugs by the ECMO circuit. Fluconazole and micafungin were studied separately in three closed-loop circuit configurations to isolate the impact of the oxygenator, hemofilter, and tubing on circuit extraction. Each circuit was primed with human blood, and flow was set to 1 L/min. Drug was dosed to achieve therapeutic concentrations. Each antifungal was added to a separate tube of blood to serve as a control. Serial blood samples were collected over 24 hours and concentrations were quantified with a validated assay. Drug recovery was calculated at each time point: (C t /C i )*100, with C t and C i the concentrations at time = t and 1 minute, respectively. After 24 hours of recirculation, mean recovery of fluconazole in the ECMO circuit (95-98%) and controls (101%) was high. In contrast, mean recovery of micafungin was dependent on the time and circuit configuration. Recovery at 4 hours was only 46% when a hemofilter was in-line but was much higher when the hemofilter was removed (91%). By 24 hours, however, micafungin recovery was low in all circuit configurations (26-43%), regardless of the presence of a hemofilter, as well as in the controls (57%). In conclusion, these results suggest that micafungin is extracted by the ECMO circuit, which may result in decreased drug exposure in vivo.

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.

Non-maturational covariates for dynamic systems pharmacology models in neonates, infants, and children: Filling the gaps beyond developmental pharmacology

Pharmacokinetics and -dynamics show important changes throughout childhood. Studies on the different maturational processes that influence developmental pharmacology have been used to create population PK/PD models that can yield individualized pediatric drug dosages. These models were subsequently translated to semi-physiologically or physiology-based PK (PBPK) models that support predictions in pediatric patient cohorts and other special populations. Although these translational efforts are crucial, these models should be further improved towards individual patient predictions by including knowledge on non-maturational covariates. These efforts are needed to ultimately get to systems pharmacology models for children. These models take developmental changes relating to the pediatric dynamical system into account but also other aspects that may be of importance such as abnormal body composition, pharmacogenetics, critical illness and inflammatory status.

Clinical Pharmacology Studies in Critically Ill Children

Developmental and physiological changes in children contribute to variation in drug disposition with age. Additionally, critically ill children suffer from various life-threatening conditions that can lead to pathophysiological alterations that further affect pharmacokinetics (PK). Some factors that can alter PK in this patient population include variability in tissue distribution caused by protein binding changes and fluid shifts, altered drug elimination due to organ dysfunction, and use of medical interventions that can affect drug disposition (e.g., extracorporeal membrane oxygenation and continuous renal replacement therapy). Performing clinical studies in critically ill children is challenging because there is large inter-subject variability in the severity and time course of organ dysfunction; some critical illnesses are rare, which can affect subject enrollment; and critically ill children usually have multiple organ failure, necessitating careful selection of a study design. As a result, drug dosing in critically ill children is often based on extrapolations from adults or non-critically ill children. Dedicated clinical studies in critically ill children are urgently needed to identify optimal dosing of drugs in this vulnerable population. This review will summarize the effect of critical illness on pediatric PK, the challenges associated with performing studies in this vulnerable subpopulation, and the clinical PK studies performed to date for commonly used drugs.

Pharmacokinetics and Dosing of Anti-infective Drugs in Patients on Extracorporeal Membrane Oxygenation: A Review of the Current Literature

PURPOSE

Extracorporeal membrane oxygenation (ECMO) is a cardiopulmonary bypass device that is used to temporarily support the most critically ill of patients with respiratory and/or cardiac failure. Infection and its sequelae may be an indication for ECMO or infections may be acquired while on ECMO and are associated with a mortality >50%. Effective therapy requires optimal dosing. However, optimal dosing can be different in patients on ECMO because the ECMO circuit can alter drug pharmacokinetics. This review assessed the current literature for pharmacokinetic data and subsequent dosing recommendations for anti-infective drugs in patients on ECMO.

METHODS

We searched the PubMed and Embase databases (1965 to February 2016) and included case reports, case series, or studies that provided pharmacokinetic data for anti-infective drugs including antibiotics, antifungals, and antivirals being used to treat patients of all age groups on ECMO. Pharmacokinetic parameters and dosing recommendations based on these data are presented.

FINDINGS

The majority of data on this topic comes from neonatal studies of antibiotics from the 1980s and 1990s. These studies generally demonstrate a larger volume of distribution due to ECMO and therefore higher doses are needed initially. More adult data are now emerging, but with a predominance of case reports and case series without comparison with critically ill controls. The available pharmacokinetic analyses do suggest that volume of distribution and clearance are unchanged in the adult population, and therefore dosing recommendations largely remain unchanged. There is a lack of data on children older than 1 year of age. The data support the importance of therapeutic drug monitoring when available in this population of patients.

IMPLICATIONS

This review found reasonably robust dosing recommendations for some drugs and scant or no data for other important anti-infectives. In order to better determine optimal dosing for patients on ECMO, a systematic approach is needed. Approaches that combine ex vivo ECMO experiments, animal studies, specialized pharmacokinetic modeling, and human clinical trials are being developed.

Advances in Pediatric Pharmacology, Therapeutics, and Toxicology

In the United States, the Best Pharmaceuticals for Children Act and the Pediatric Research Equity Act continue to promote clinical trials in pediatric populations across all age ranges. In 2014 and 2015, over 70 changes were made to drug labels with updates on information regarding pediatric populations. Additionally, multiple new therapies have received first-approvals for the treatment of pediatric indications ranging form rare genetic metabolic diseases to oncology. In the European Union, there have been more than 30 new authorizations for medicines used in children and 130 approved pediatric investigation plans. Despite the progress that has been made over the last two years, much work remains to further the development of safe and effective therapies for pediatric patients.

Pharmacokinetics/pharmacodynamic correlations of fluconazole in murine model of cryptococcosis

The emergence of fluconazole-resistant Cryptococcus gattii is a global concern, since this azole is the main antifungal used worldwide to treat patients with cryptococcosis. Although pharmacokinetic (PK) and pharmacodynamic (PD) indices are useful predictive factors for therapeutic outcomes, there is a scarcity of data regarding PK/PD analysis of antifungals in cryptococcosis caused by resistant strains. In this study, PK/PD parameters were determined in a murine model of cryptococcosis caused by resistant C. gattii. We developed and validated a suitable liquid chromatography-electrospray ionization tandem mass spectrometry method for PK studies of fluconazole in the serum, lungs, and brain of uninfected mice. Mice were infected with susceptible or resistant C. gattii, and the effects of different doses of fluconazole on the pulmonary and central nervous system fungal burden were determined. The peak levels in the serum, lungs, and brain were achieved within 0.5h. The AUC/MIC index (area under the curve/minimum inhibitory concentration) was associated with the outcome of anti-cryptococcal therapy. Interestingly, the maximum concentration of fluconazole in the brain was lower than the MIC for both strains. In addition, the treatment of mice infected with the resistant strain was ineffective even when high doses of fluconazole were used or when amphotericin B was tested, confirming the cross-resistance between these drugs. Altogether, our novel data provide the correlation of PK/PD parameters with antifungal therapy during cryptococcosis caused by resistant C. gattii.

Fungal infections in children in the early postoperative period after cardiac surgery for congenital heart disease: a single-centre experience

OBJECTIVES

Postoperative infections are still an important problem in cardiac surgery, especially in the paediatric population, and may influence the final outcome of congenital heart disease treatment. Postoperative infections with fungi are uncommon. The aetiology is poorly understood, and the proper diagnosis and treatment is unclear. In this single-centre study, the frequency of invasive fungal disease in children who underwent surgical management of congenital heart diseases was determined along with the risk factors for infection, treatment options and outcomes.

METHODS

All consecutive paediatric patients (<18 years of age) who underwent cardiac surgery for congenital heart disease between September 2008 and December 2015 in a paediatric cardiac centre in Poland were identified. Those who developed invasive fungal disease in the early postoperative period (30 days) were identified.

RESULTS

Of the 1540 cardiosurgical procedures for congenital heart disease, 6 were complicated by fungal infection (0.39%). One patient had a high probability of fungal infection, but the diagnosis was unproved. Nevertheless, the patient was successfully treated with antifungal treatment. Five had proven invasive fungal disease. Of these, 3 were diagnosed with candidaemia. All had undergone cardiopulmonary bypass. Of the remaining 2 patients, 1 was a preterm newborn with complete atrioventricular septal defect who developed rib fungal invasion. The remaining patient had pulmonary atresia with ventricular septal defect and developed Fournier's gangrene after surgery. None of the patients died due to infection in the early postoperative period. However, the child with rib fungal invasion died 39 days after surgery as a result of multiorgan failure.

CONCLUSIONS

Fungal infections in paediatric patients after cardiac surgery may markedly influence morbidity and mortality. Fungal infection prophylaxis in this specific group of children may reduce morbidity, whereas early empirical treatment followed by a targeted approach may improve outcomes. The 'hit fast, hit hard' treatment strategy may be the best rescue option for children who develop invasive fungal disease after cardiac surgery.