Pharmacokinetics and safety of fluconazole in young infants supported with extracorporeal membrane oxygenation

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.

Pharmacokinetics of Commonly Used Antimicrobials in Critically Ill Pediatric Patients During Extracorporeal Membrane Oxygenation: A Systematic Review

PURPOSE

Adequate dosing of antimicrobials is critical to properly treat infections and limit development of resistance and adverse effects. Limited guidance exist for antimicrobial dosing adjustments in patients requiring extracorporeal membrane oxygenation (ECMO) therapy, particularly in the pediatric population. A systematic review was conducted to delineate the pharmacokinetics (PK) and pharmacodynamics (PD) of antimicrobials in critically ill neonates and children requiring ECMO therapy.

METHODS

Medline, EMBASE, Global Health and All EBM Reviews databases were queried. Grey literature was examined. All clinical studies reporting PK/PD parameters of antimicrobials in critically ill pediatric patients treated with ECMO were included, except for case reports and congress abstracts. Two independent reviewers applied the inclusion and exclusion criteria. Reviewers were then paired to independently extract data and evaluate the methodological quality of studies using the ROBINS-I tool and the compliance with ClinPK reporting guidelines. Patient and study characteristics, key PK/PD findings, details of ECMO circuits and co-treatments were summarized qualitatively. Broad dosing recommendations were formulated based on the available data for specific antimicrobials.

RESULTS

Twenty-nine clinical studies were included; most were observational and uncontrolled. Patient characteristics and co-treatments were often missing. The effect of ECMO on PK/PD parameters of antimicrobials varied depending on the drugs and population studied. It was only possible to formulate dosing recommendations for a few antimicrobials given the paucity of data, its overall low quality and heterogeneity in reporting.

CONCLUSION

Limited data exists on the PK/PD of antimicrobials during ECMO therapy in the pediatric population. Rigorously designed population PK studies are required to establish empiric dosing guidelines for antimicrobials in patients requiring this therapeutic modality. The use of therapeutic drug monitoring for antimicrobials in pediatric patients on ECMO should be encouraged to optimize dosing.

TRIAL REGISTRY

PROSPERO registration number: CRD42018099992 (Registered: July 24th 2018).

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.

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.

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.

Safety of sildenafil in extremely premature infants: a phase I trial

OBJECTIVE

To characterize the safety of sildenafil in premature infants.

STUDY DESIGN

A phase I, open-label trial of sildenafil in premature infants receiving sildenafil per usual clinical care (cohort 1) or receiving a single IV dose of sildenafil (cohort 2). Safety was evaluated based on adverse events (AEs), transaminase levels, and mean arterial pressure monitoring.

RESULTS

Twenty-four infants in cohort 1 (n = 25) received enteral sildenafil. In cohort 2, infants received a single IV sildenafil dose of 0.25 mg/kg (n = 7) or 0.125 mg/kg (n = 2). In cohort 2, there was one serious AE related to study drug involving hypotension associated with a faster infusion rate than specified by the protocol. There were no AEs related to elevated transaminases.

CONCLUSION

Sildenafil was well tolerated by the study population. Drug administration times and flush rates require careful attention to prevent infusion-related hypotension associated with faster infusions of IV sildenafil in premature infants.

CLINICAL TRIAL

ClinicalTrials.gov Identifier: NCT01670136.

Machines that help machines to help patients: optimising antimicrobial dosing in patients receiving extracorporeal membrane oxygenation and renal replacement therapy using dosing software

Intensive care unit (ICU) patients with end-organ failure will require specialised machines or extracorporeal therapies to support the failing organs that would otherwise lead to death. ICU patients with severe acute kidney injury may require renal replacement therapy (RRT) to remove fluid and wastes from the body, and patients with severe cardiorespiratory failure will require extracorporeal membrane oxygenation (ECMO) to maintain adequate oxygen delivery whilst the underlying pathology is evaluated and managed. The presence of ECMO and RRT machines can further augment the existing pharmacokinetic (PK) alterations during critical illness. Significant changes in the apparent volume of distribution (V_d) and drug clearance (CL) for many important drugs have been reported during ECMO and RRT. Conventional antimicrobial dosing regimens rarely consider the impact of these changes and consequently, are unlikely to achieve effective antimicrobial exposures in critically ill patients receiving ECMO and/or RRT. Therefore, an in-depth understanding on potential PK changes during ECMO and/or RRT is required to inform antimicrobial dosing strategies in patients receiving ECMO and/or RRT. In this narrative review, we aim to discuss the potential impact of ECMO and RRT on the PK of antimicrobials and antimicrobial dosing requirements whilst receiving these extracorporeal therapies. The potential benefits of therapeutic drug monitoring (TDM) and dosing software to facilitate antimicrobial therapy for critically ill patients receiving ECMO and/or RRT are also reviewed and highlighted.

[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.

Core Recommendations for Antifungal Stewardship: A Statement of the Mycoses Study Group Education and Research Consortium

In recent years, the global public health community has increasingly recognized the importance of antimicrobial stewardship (AMS) in the fight to improve outcomes, decrease costs, and curb increases in antimicrobial resistance around the world. However, the subject of antifungal stewardship (AFS) has received less attention. While the principles of AMS guidelines likely apply to stewarding of antifungal agents, there are additional considerations unique to AFS and the complex field of fungal infections that require specific recommendations. In this article, we review the literature on AMS best practices and discuss AFS through the lens of the global core elements of AMS. We offer recommendations for best practices in AFS based on a synthesis of this evidence by an interdisciplinary expert panel of members of the Mycoses Study Group Education and Research Consortium. We also discuss research directions in this rapidly evolving field. AFS is an emerging and important component of AMS, yet requires special considerations in certain areas such as expertise, education, interventions to optimize utilization, therapeutic drug monitoring, and data analysis and reporting.

The role of antibiotic pharmacokinetic studies performed post-licensing

Post-licensing pharmacometric studies can provide a better understanding of the pharmacokinetic (PK) alterations in special patient populations and may lead to better clinical outcomes. Some patient populations exhibit markedly different pathophysiology to general ward patients or healthy individuals. This may be developmental (paediatric patients), a manifestation of an underlying disease pathology (patients with obesity or haematological malignancies) or due to medical interventions (critically ill patients receiving extracorporeal therapies). This paper outlines the factors that affect the PK of special patient populations and describes some novel methods of antimicrobial administration that may increase antimicrobial concentrations at the site of infection and improve treatment of severe infection.

Pharmacokinetics of micafungin in patients treated with extracorporeal membrane oxygenation: an observational prospective study

Objective

To determine micafungin plasma levels and pharmacokinetic behavior in patients treated with extracorporeal membrane oxygenation.

Methods

The samples were taken through an access point before and after the membrane in two tertiary hospitals in Spain. The times for the calculation of pharmacokinetic curves were before the administration of the drug and 1, 3, 5, 8, 18 and 24 hours after the beginning of the infusion on days one and four. The area under the curve, drug clearance, volume of distribution and plasma half-life time with a noncompartmental pharmacokinetic data analysis were calculated.

Results

The pharmacokinetics of the values analyzed on the first and fourth day of treatment did not show any concentration difference between the samples taken before the membrane (Cin) and those taken after the membrane (Cout), and the pharmacokinetic behavior was similar with different organ failures. The area under the curve (AUC) before the membrane on day 1 was 62.1 (95%CI 52.8 - 73.4) and the AUC after the membrane on this day was 63.4 (95%CI 52.4 - 76.7), p = 0.625. The AUC before the membrane on day 4 was 102.4 (95%CI 84.7 - 142.8) and the AUC was 100.9 (95%CI 78.2 - 138.8), p = 0.843.

Conclusion

The pharmacokinetic parameters of micafungin were not significantly altered.

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.

Drug Disposition and Pharmacotherapy in Neonatal ECMO: From Fragmented Data to Integrated Knowledge

Extracorporeal membrane oxygenation (ECMO) is a lifesaving support technology for potentially reversible neonatal cardiac and/or respiratory failure. As the survival and the overall outcome of patients rely on the treatment and reversal of the underlying disease, effective and preferentially evidence-based pharmacotherapy is crucial to target recovery. Currently limited data exist to support the clinicians in their every-day intensive care prescribing practice with the contemporary ECMO technology. Indeed, drug dosing to optimize pharmacotherapy during neonatal ECMO is a major challenge. The impact of the maturational changes of the organ function on both pharmacokinetics (PK) and pharmacodynamics (PD) has been widely established over the last decades. Next to the developmental pharmacology, additional non-maturational factors have been recognized as key-determinants of PK/PD variability. The dynamically changing state of critical illness during the ECMO course impairs the achievement of optimal drug exposure, as a result of single or multi-organ failure, capillary leak, altered protein binding, and sometimes a hyperdynamic state, with a variable effect on both the volume of distribution (Vd) and the clearance (Cl) of drugs. Extracorporeal membrane oxygenation introduces further PK/PD perturbation due to drug sequestration and hemodilution, thus increasing the Vd and clearance (sequestration). Drug disposition depends on the characteristics of the compounds (hydrophilic vs. lipophilic, protein binding), patients (age, comorbidities, surgery, co-medications, genetic variations), and circuits (roller vs. centrifugal-based systems; silicone vs. hollow-fiber oxygenators; renal replacement therapy). Based on the potential combination of the above-mentioned drug PK/PD determinants, an integrated approach in clinical drug prescription is pivotal to limit the risks of over- and under-dosing. The understanding of the dose-exposure-response relationship in critically-ill neonates on ECMO will enable the optimization of dosing strategies to ensure safety and efficacy for the individual patient. Next to in vitro and clinical PK data collection, physiologically-based pharmacokinetic modeling (PBPK) are emerging as alternative approaches to provide bedside dosing guidance. This article provides an overview of the available evidence in the field of neonatal pharmacology during ECMO. We will identify the main determinants of altered PK and PD, elaborate on evidence-based recommendations on pharmacotherapy and highlight areas for further research.

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.

Overcoming barriers to optimal drug dosing during ECMO in critically ill adult patients

INTRODUCTION

One major challenge to achieving optimal patient outcome in extracorporeal membrane oxygenation (ECMO) is the development of effective dosing strategies in this critically ill patient population. Suboptimal drug dosing impacts on patient outcome as patients on ECMO often require reversal of the underlying pathology with effective pharmacotherapy in order to be liberated of the life-support device. Areas covered: This article provides a concise review of the effective use of antibiotics, analgesics, and sedative by characterizing the specific changes in PK secondary to the introduction of the ECMO support. We also discuss the barriers to achieving optimal pharmacotherapy in patients on ECMO and also the current and potential research that can be undertaken to address these clinical challenges. Expert opinion: Decreased bioavailability due to sequestration of drugs in the ECMO circuit and ECMO induced PK alterations are both significant barriers to optimal drug dosing. Evidence-based drug choices may minimize sequestration in the circuit and would enable safety and efficacy to be maintained. More work to characterize ECMO related pharmacodynamic alterations such as effects of ECMO on hepatic cytochrome system are still needed. Novel techniques to increase target site concentrations should also be explored.

Oxygenator Impact on Ceftaroline in Extracorporeal Membrane Oxygenation Circuits

OBJECTIVES

To determine the oxygenator impact on alterations of ceftaroline in a contemporary neonatal/pediatric (1/4-inch) and adolescent/adult (3/8-inch) extracorporeal membrane oxygenation circuit including the Quadrox-i oxygenator (Maquet, Wayne, NJ).

DESIGN

Quarter-inch and 3/8-inch, simulated closed-loop extracorporeal membrane oxygenation circuits were prepared with a Quadrox-i pediatric and Quadrox-i adult oxygenator and blood primed. Additionally, 1/4-inch and 3/8-inch circuits were also prepared without an oxygenator in series. An one-time dose of ceftaroline was administered into the circuits, and serial pre- and postoxygenator concentrations were obtained at 5 minutes, 1-, 2-, 3-, 4-, 5-, 6-, and 24-hour time points. Ceftaroline was also maintained in a glass vial, and samples were taken from the vial at the same time periods for control purposes to assess for spontaneous drug degradation.

SETTING

A free-standing extracorporeal membrane oxygenation circuit.

PATIENTS

None.

INTERVENTION

Single dose administration of ceftaroline into closed-loop extracorporeal membrane oxygenation circuits prepared with and without an oxygenator in series with serial preoxygenator, postoxygenator, and reference samples obtained for concentration determination over a 24-hour study period.

MEASUREMENTS AND MAIN RESULTS

For the 1/4-inch circuit with an oxygenator, there was 79.8% drug loss preoxygenator and 82.5% drug loss postoxygenator at 24 hours. There was a statistically significant difference (p < 0.01) in the amount of ceftaroline remaining at 24 hours when compared with each prior time point for the 1/4-inch circuit. For the 1/4-inch circuit without an oxygenator, there was no significant drug loss at any study time point. For the 3/8-inch circuit with an oxygenator, there was 76.2% drug loss preoxygenator and 77.6% drug loss postoxygenator at 24 hours. There was a statistically significant difference (p < 0.01) in the amount of ceftaroline remaining at 24 hours when compared with each prior time point for the 3/8-inch circuit. For the 3/8-inch circuit without an oxygenator, there was no significant drug loss at any study time point. The reference ceftaroline concentrations remained relatively constant during the entire study period demonstrating the ceftaroline loss in each size of the extracorporeal membrane oxygenation circuit with or without an oxygenator was not a result of spontaneous drug degradation and primarily the result of the oxygenator.

CONCLUSIONS

This ex vivo investigation demonstrated significant ceftaroline loss within an extracorporeal membrane oxygenation circuit with an oxygenator in series with both sizes of the Quadrox-i oxygenator at 24 hours. Therapeutic concentrations of ceftaroline in the setting of extracorporeal membrane oxygenation may not be achieved with current U.S. Food and Drug Administration-recommended doses, and further evaluation is needed before specific drug dosing recommendations can be made for clinical application with extracorporeal membrane oxygenation.

Suggestions for Model-Informed Precision Dosing to Optimize Neonatal Drug Therapy

Evidence for dosing, efficacy, and safety of most medications used to treat neonates is sparse. Thus, dosing is usually derived by extrapolation from adult and pediatric pharmacologic data with scaling by body weight or body surface area. This may lead to drug dosing that is unsafe or ineffective. However, new strategies are being developed and studied to dose medications in critically ill neonates. Mass spectroscopy technology capable of quickly analyzing drug levels is readily available. Software that integrates population pharmacokinetics and pharmacodynamics with data from sparse samples from neonates allows for timely adjustments of dosing to achieve the desired effect while minimizing adverse outcomes. Some genetic polymorphisms that affect drug response in neonates have also been reported. This review highlights aspects of drug response and how it is impacted by prematurity, assesses pharmacogenomic studies in neonates, and offers suggestions for innovative pharmacokinetic/pharmacodynamic model-based approaches that combine population- or physiology-based pharmacology data, Bayesian analysis, and electronic decision support tools for precision dosing in neonates while illustrating examples where this approach can be used to optimize medical therapy in neonates. Barriers to implementing precision dosing in neonates and how to overcome them are also discussed.

Safety and Tolerability of Moxifloxacin in Children

OBJECTIVES

Moxifloxacin is not approved by the US Food and Drug Administration for pediatric use. Although its use might be indicated under certain conditions, data regarding its safety and tolerability in pediatric patients are limited. The primary objective of this study was to evaluate the safety of systemic moxifloxacin therapy in children.

METHODS

We conducted a retrospective observational study of patients aged <18 years who received oral or intravenous moxifloxacin at our institution between January 2011 and July 2016. Patient demographics, clinical characteristics, indication for moxifloxacin use, and adverse events (AEs) were extracted via chart review. The attribution of AEs to moxifloxacin use was adjudicated in consultation with a pediatric infectious disease (ID) pharmacist.

RESULTS

We identified 221 patients who received 300 courses of moxifloxacin. The average age at moxifloxacin initiation was 10.4 years. One or more AEs occurred during 195 (65%) of the courses. Of the 463 distinct AEs, 46 (9.9%) were attributed to moxifloxacin. AEs attributed to moxifloxacin included corrected QT interval (QTc) prolongation (18 [6%] courses), transaminase level elevation (7 [2.3%] courses), and increased bilirubin level (3 [1%] courses). AEs led to moxifloxacin discontinuation in 18 (6%) courses. ID consultation was associated with QTc (P < .001) and transaminase (P = .002) monitoring.

CONCLUSIONS

AEs that occur during pediatric moxifloxacin therapy are relatively common but rarely serious enough to require premature discontinuation. The drug might be used safely in most children with monitoring, including evaluation for QTc prolongation, and guidance from ID specialists.

Impact of ex-vivo extracorporeal membrane oxygenation circuitry on daptomycin

Background:

The objective was to determine the alterations of daptomycin (DAP) in a contemporary neonatal/pediatric (1/4-inch) and adolescent/adult (3/8-inch) extracorporeal membrane oxygenation (ECMO) circuit including the Quadrox-i® oxygenator.

Methods:

Quarter-inch and 3/8-inch, simulated, closed-loop, ECMO circuits were prepared with a Quadrox-i pediatric and Quadrox-i adult oxygenator and blood primed. A one-time dose of DAP was administered into the circuit and serial pre- and post-oxygenator concentrations were obtained at 0-5 minutes and 1, 2, 3, 4, 5, 6 and 24-hour time points. DAP was also maintained in a glass vial and samples were taken from the vial at the same time periods for control purposes to assess for spontaneous drug degradation

Results:

For both the 1/4-inch and 3/8-inch circuits, there was no significant DAP loss at 24 hours. Additionally, the reference DAP concentrations remained relatively constant during the entire 24-hour study period.

Conclusion:

This ex-vivo investigation demonstrated no significant DAP loss within an ECMO circuit with both sizes of the Quadrox-i oxygenator at 24 hours. Therapeutic concentrations of DAP in the setting of ECMO may be anticipated with current recommended doses, depending on the amount of extracorporeal volume needed for circuit maintenance in comparison to the patient’s apparent volume of distribution. Additional studies with a larger sample size are needed to confirm these findings.

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.

Pediatric Multiple Organ Dysfunction Syndrome: Promising Therapies

OBJECTIVE

To describe the state of the science, identify knowledge gaps, and offer potential future research questions regarding promising therapies for children with multiple organ dysfunction syndrome presented during the Eunice Kennedy Shriver National Institute of Child Health and Human Development Workshop on Pediatric Multiple Organ Dysfunction Syndrome (March 26-27, 2015).

DATA SOURCES

Literature review, research data, and expert opinion.

STUDY SELECTION

Not applicable.

DATA EXTRACTION

Moderated by an expert from the field, issues relevant to the association of multiple organ dysfunction syndrome with a variety of conditions were presented, discussed, and debated with a focus on identifying knowledge gaps and research priorities.

DATA SYNTHESIS

Summary of presentations and discussion supported and supplemented by relevant literature.

CONCLUSIONS

Among critically ill children, multiple organ dysfunction syndrome is relatively common and associated with significant morbidity and mortality. For outcomes to improve, effective therapies aimed at preventing and treating this condition must be discovered and rigorously evaluated. In this article, a number of potential opportunities to enhance current care are highlighted including the need for a better understanding of the pharmacokinetics and pharmacodynamics of medications, the effect of early and optimized nutrition, and the impact of effective glucose control in the setting of multiple organ dysfunction syndrome. Additionally, a handful of the promising therapies either currently being implemented or developed are described. These include extracorporeal therapies, anticytokine therapies, antitoxin treatments, antioxidant approaches, and multiple forms of exogenous steroids. For the field to advance, promising therapies and other therapies must be assessed in rigorous manner and implemented accordingly.

Pharmacokinetics and Safety of Micafungin in Infants Supported With Extracorporeal Membrane Oxygenation

BACKGROUND

Candida is a leading cause of infection in infants on extracorporeal membrane oxygenation (ECMO). Optimal micafungin dosing is unknown in this population because ECMO can alter drug pharmacokinetics (PK).

METHODS

To characterize micafungin pharmacokinetics and safety in infants on ECMO, we conducted an open-label pharmacokinetics trial. Infants on ECMO either received intravenous micafungin 4 mg/kg every 24 h for invasive candidiasis prophylaxis or 8 mg/kg every 24 h when a fungal infection was suspected or confirmed. We collected plasma samples after single and multiple micafungin doses. We defined the therapeutic target as the adult exposure associated with efficacy in phase III trials and the prophylactic target as one-half of the therapeutic target.

RESULTS

We enrolled 12 infants (124 samples) with a median age of 59 days. Using a 1-compartment model, median weight-normalized volume of distribution and clearance were 0.64 L/kg and 0.041 L/kg/h, respectively. Dose-exposure simulations revealed that doses of 2.5 and 5 mg/kg every 24 h matched exposure targets for prophylaxis and treatment of invasive candidiasis, respectively. We did not observe any drug-related adverse events.

CONCLUSIONS

In infants on ECMO, micafungin volume of distribution was higher and clearance was in the upper range of previously published values for infants not on ECMO. Based on these data, we recommend dosing of 2.5 and 5 mg/kg every 24 h for prophylaxis and treatment of invasive candidiasis, respectively, to match adult exposure proven effective against Candida spp.

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.

Pharmacotherapy during pediatric extracorporeal membrane oxygenation: a review

INTRODUCTION

Pediatric critical illness and associated alterations in organ function can change drug pharmacokinetics (PK). Extracorporeal membrane oxygenation (ECMO), a life-saving therapy for severe cardiac and/or respiratory failure, causes additional PK alterations that affect drug disposition.

AREAS COVERED

The purposes of this review are to discuss the PK changes that occur during ECMO, the associated therapeutic implications, and to review PK literature relevant to pediatric ECMO. We discuss various classes of drugs commonly used for pediatric patients on ECMO, including sedatives, analgesics, antimicrobials and cardiovascular drugs. Finally, we discuss future areas of research and recommend strategies for future pediatric ECMO pharmacologic investigations.

EXPERT OPINION

Clinicians caring for pediatric patients treated with ECMO must have an understanding of PK alterations that could lead to either therapeutic failures or increased drug toxicity during this life-saving therapy. Limited data currently exist for optimal drug dosing in pediatric populations who are treated with ECMO. While there are clear challenges to conducting and analyzing data associated with clinical pharmacokinetic-pharmacodynamic studies of children on ECMO, we present techniques to address these challenges. Improved understanding of the physiology and drug disposition during ECMO combined with PK-PD modeling will allow for more adaptable and individualized dosing schemes.

Optimizing operational efficiencies in early phase trials: The Pediatric Trials Network experience

Performing drug trials in pediatrics is challenging. In support of the Best Pharmaceuticals for Children Act, the Eunice Kennedy Shriver National Institute of Child Health and Human Development funded the formation of the Pediatric Trials Network (PTN) in 2010. Since its inception, the PTN has developed strategies to increase both efficiency and safety of pediatric drug trials. Through use of innovative techniques such as sparse and scavenged blood sampling as well as opportunistic study design, participation in trials has grown. The PTN has also strived to improve consistency of adverse event reporting in neonatal drug trials through the development of a standardized adverse event table. We review how the PTN is optimizing operational efficiencies in pediatric drug trials to increase the safety of drugs in children.

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

Candida infections are a leading cause of infectious disease-related death in children supported by extracorporeal membrane oxygenation (ECMO). The ECMO circuit can alter drug pharmacokinetics (PK); thus, standard fluconazole dosing may result in suboptimal drug exposures. The objective of our study was to determine the PK of fluconazole in children on ECMO. Forty children with 367 PK samples were included in the analysis. The PK data were analyzed using nonlinear mixed-effect modeling (NONMEM). A one-compartment model best described the data. Weight was included in the base model for clearance (CL) and volume of distribution (V). The final model included the effect of serum creatinine (SCR) level on CL and the effect of ECMO on V as follows: CL (in liters per hour) = 0.019 × weight × (SCR/0.4)(-0.29) × exp(ηCL) and V (in liters) = 0.93 × weight × 1.4(ECMO) × exp(ηV). The fluconazole V was increased in children supported by ECMO. Consequently, children on ECMO require a higher fluconazole loading dose for prophylaxis (12 mg/kg of body weight) and treatment (35 mg/kg) paired with standard maintenance doses to achieve exposures similar to those of children not on ECMO.

New antifungal and antiviral dosing

Neonatal fungal and viral infections are associated with mortality and neurologic impairment among survivors. Advances in pharmacokinetics (PK) and pharmacodynamics (PD) of antimicrobial medications have led to improved dosing guidance for neonates. This article discusses the basic PK/PD properties and dosing of the most common antifungal and antiviral medications used in neonates.

Dosing in neonates: special considerations in physiology and trial design

Determining the right dose for drugs used to treat neonates is critically important. Neonates have significant differences in physiology affecting drug absorption, distribution, metabolism, and elimination that make extrapolating dosages from adults and older children inappropriate. In spite of recent legislative efforts requiring drug studies in this population, most drugs given to neonates remain insufficiently studied. Many ethical and logistical concerns make designing studies in this age group difficult. Fortunately, specialized analytical techniques, such as the use of dried blood spots, scavenged sampling, population pharmacokinetics analyses, and sparse sampling, have helped investigators better define doses that maximize efficacy and safety. Through the use of these methods, successful clinical trials have resulted in recent changes to drug dosing in this population.

Advances in pediatric pharmacology, therapeutics, and toxicology

In the United States, passage of the FDASIA legislation made BPCA and PREA permanent, no longer requiring reauthorization every 5 years. This landmark legislation also stressed the importance of performing clinical trials in neonates when appropriate. In Europe the Pediatric Regulation, which went into effect in early 2007, also provides a framework for expanding pediatric clinical research. Although much work remains, as a result of greater regulatory guidance more pediatric data are reaching product labels.