Pharmacokinetics, safety, and tolerability of voriconazole in immunocompromised children

The Clinical Significance of Voriconazole Therapeutic Drug Monitoring in Children With Invasive Fungal Infections

Voriconazole is an antifungal drug used to treat fungal infections. This was a retrospective study of 61 children with hemato-oncologic diseases or solid organ transplantation who were administered voriconazole for invasive fungal infections. Of the 61 patients, 31 (50.8%) were in the therapeutic drug monitoring (TDM) group, and 30 (49.2%) were in the non-TDM group. At 12 weeks, treatment failure rate in the non-TDM group was higher than the TDM group (78.6% versus 40.0%, p = 0.038). Drug discontinuation due to adverse events was less frequent in the TDM group than the non-TDM group (26.0% versus 92.3%, p = 0.001). Children required higher dosages to maintain drug levels within the targeted therapeutic range: an average of 8.3 mg/kg/dose in patients <12 years old and 6.9 mg/kg/dose for those ≥12 years old. Treatment failure rates were higher in patients whose voriconazole levels remained below 1.0 mg/L for more than 50% of their treatment duration than those above 1.0 mg/L (71.4% vs. 9.1% after 12 weeks, p = 0.013). Serial monitoring of voriconazole levels in children is important for improving treatment response and preventing unnecessary drug discontinuation. Higher dosages are needed in children to reach therapeutic range.

Use of Fungal Diagnostics and Therapy in Pediatric Cancer Patients in Resource-Limited Settings

Fungal diseases are an important cause of mortality in immunocompromised hosts, and their incidence in pediatric cancer patients in low- to middle-income countries is underestimated. In this review, we present relevant, up-to-date information about the most common opportunistic and endemic fungal diseases among children with cancer, their geographic distribution, and recommended diagnostics and treatment. Efforts to improve the care of children with cancer and fungal disease must address the urgent need for sustainable and cost-effective solutions that improve training, fungal disease testing capability, and the use of available resources. We hope that the collective information presented here will be used to advise healthcare providers, regional and country health leaders, and policymakers of the current challenges in diagnosing and treating fungal infections in children with cancer in low- to middle-income countries.

Practice Guidelines for the Diagnosis and Management of Aspergillosis: 2016 Update by the Infectious Diseases Society of America

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.

Pediatric Invasive Aspergillosis

Invasive aspergillosis (IA) is a disease of increasing importance in pediatrics due to growth of the immunocompromised populations at risk and improvements in long-term survival for many of these groups. While general principles of diagnosis and therapy apply similarly across the age spectrum, there are unique considerations for clinicians who care for children and adolescents with IA. This review will highlight important differences in the epidemiology, clinical manifestations, diagnosis, and therapy of pediatric IA.

Pharmacokinetic/pharmacodynamic analysis of voriconazole against Candida spp. and Aspergillus spp. in children, adolescents and adults by Monte Carlo simulation

The objective of this study was to investigate the cumulative fraction of response of various voriconazole dosing regimens against six Candida and six Aspergillus spp. in immunocompromised children, immunocompromised adolescents, and adults. Using pharmacokinetic parameters and pharmacodynamic data, 5000-subject Monte Carlo simulations (MCSs) were conducted to evaluate the ability of simulated dosing strategies in terms of fAUC/MIC targets of voriconazole. According to the results of the MCSs, current voriconazole dosage regimens were all effective for children, adolescents and adults against Candida albicans, Candida parapsilosis and Candida orthopsilosis. For adults, dosing regimens of 4 mg/kg intravenous every 12 h (q12h) and 300 mg orally q12h were sufficient to treat fungal infections by six Candida spp. (C. albicans, C. parapsilosis, Candida tropicalis, Candida glabrata, Candida krusei and C. orthopsilosis) and five Aspergillus spp. (Aspergillus fumigatus, Aspergillus flavus, Aspergillus terreus, Aspergillus niger and Aspergillus nidulans). However, high doses should be recommended for children and adolescents in order to achieve better clinical efficacy against A. fumigatus and A. nidulans. The current voriconazole dosage regimens were all ineffective against A. niger for children and adolescents. All voriconazole dosage regimens were not optimal against Aspergillus versicolor. This is the first study to evaluate clinical therapy of various voriconazole dosing regimens against Candida and Aspergillus spp. infections in children, adolescents and adults using MCS. The pharmacokinetic/pharmacodynamic-based dosing strategy provided a theoretical rationale for identifying optimal voriconazole dosage regimens in children, adolescents and adults in order to maximise clinical response and minimise the probability of exposure-related toxicity.

Pharmacokinetic considerations in treating invasive pediatric fungal infections

INTRODUCTION

Despite the increased availability of systemic antifungal agents in recent years, the management of invasive fungal disease is still associated with significant morbidity and mortality. Knowledge of a drug's pharmacokinetic behavior is critical for optimizing existing treatment strategies.

AREAS COVERED

This review examines the pharmacokinetics of the major drug classes used to treat invasive mycoses including the echinocandins, imidazoles, triazoles, nucleoside analogs, and polyenes. It examines the mechanisms behind dose-exposure profiles that differ in children as compared with adults and explores the utility of pharmacogenetic testing and therapeutic drug monitoring.

EXPERT OPINION

Lifesaving medical advances for oncologic and autoimmune conditions have resulted in a significant increase in the frequency of opportunistic fungal infections. Owing to the high rate of treatment failures observed when managing invasive fungal infections, strategies to optimize antifungal therapy are critical when caring for these complex patients. Opportunities to maximize positive outcomes include dose refinement based on age or genetic status, formulation selection, co-administration of interacting medications, and administration with regard to food. The application of therapeutic drug monitoring for dose individualization is a valuable strategy to achieve pharmacodynamic targets.

Autoinduction of voriconazole metabolism in a child with invasive pulmonary aspergillosis

Inter- and intra-patient variability in voriconazole pharmacokinetics has been described in children as the result of age-specific differences in hepatic metabolism, saturable nonlinear pharmacokinetics, CYP450 2C19 polymorphisms, decreased bioavailability compared with adults, and drug-drug interactions. We introduce dose-dependent autoinduction of metabolism as another cause for altered voriconazole pharmacokinetics in children and summarize previously published literature on this phenomenon. A 10-year-old girl with severe aplastic anemia developed invasive pulmonary aspergillosis after high-dose cyclophosphamide therapy and required high doses of voriconazole for longer than 2 months. She initially achieved a therapeutic trough of 1.4 μg/ml on voriconazole 11 mg/kg/dose orally every 12 hours but required dose escalations to 9.3 mg/kg/dose orally every 8 hours to maintain a trough above 1 μg/ml. Because there were no changes in concomitant medications, route of administration, adherence, or oral intake, we conclude that the only plausible explanation for the precipitous drop in voriconazole troughs was autoinduction of metabolism, a phenomenon previously reported in adults receiving higher than usual doses or prolonged courses (longer than 2 months). These data highlight the need for continued therapeutic drug monitoring of voriconazole after initial therapeutic troughs are achieved because autoinduction of metabolism can lead to significant declines in subsequent voriconazole troughs, potentially leading to treatment failure.

In vitro study of the variable effects of proton pump inhibitors on voriconazole

Voriconazole is a broad-spectrum antifungal agent used for the treatment of severe fungal infections. Maintaining therapeutic concentrations of 1 to 5.5 μg/ml is currently recommended to maximize the exposure-response relationship of voriconazole. However, this is challenging, given the highly variable pharmacokinetics of the drug, which includes metabolism by cytochrome P450 (CYP450) isotypes CYP2C19, CYP3A4, and CYP2C9, through which common metabolic pathways for many medications take place and which are also expressed in different isoforms with various metabolic efficacies. Proton pump inhibitors (PPIs) are also metabolized through these enzymes, making them competitive inhibitors of voriconazole metabolism, and coadministration with voriconazole has been reported to increase total voriconazole exposure. We examined the effects of five PPIs (rabeprazole, pantoprazole, lansoprazole, omeprazole, and esomeprazole) on voriconazole concentrations using four sets of human liver microsomes (HLMs) of different CYP450 phenotypes. Overall, the use of voriconazole in combination with any PPI led to a significantly higher voriconazole yield compared to that achieved with voriconazole alone in both pooled HLMs (77% versus 59%; P < 0.001) and individual HLMs (86% versus 76%; P < 0.001). The mean percent change in the voriconazole yield from that at the baseline after PPI exposure in pooled microsomes ranged from 22% with pantoprazole to 51% with esomeprazole. Future studies are warranted to confirm whether and how the deliberate coadministration of voriconazole and PPIs can be used to boost voriconazole levels in patients with difficult-to-treat fungal infections.

Invasive Fusariosis: A Single Pediatric Center 15-Year Experience

Invasive fungal infection (IFI) is an important cause of mortality in immunocompromised children, particularly after hematopoietic stem cell transplantation. We describe 5 cases of Fusarium IFI in immunocompromised children seen at our institution over a 15-year period. A summary of all published pediatric cases of invasive Fusarium infection is presented. A focus on antifungal management challenges in these patients will be discussed.

Clinical pharmacology of antifungal agents to overcome drug resistance in pediatric patients

INTRODUCTION

Antifungal resistance is an emerging problem that increases morbidity and mortality in immunosuppressed pediatric patients, who suffer from invasive fungal diseases. Optimal pharmacological management is critical for the successful treatment of invasive fungal infections by resistant strains.

AREAS COVERED

This paper reviews the mechanisms of resistance of different classes of antifungal agents and the current understanding of pediatric antifungal pharmacology for overcoming antifungal resistance in children based on laboratory and clinical studies in the English literature. The therapeutic choices against fungal pathogens with intrinsic or acquired resistance are further reviewed.

EXPERT OPINION

There is a paucity of data in the pediatric population regarding the epidemiology of the resistant organisms to different antifungal agents. It is also unknown if there are more prevalent molecular mechanisms that promote antifungal resistance. Selection and dosages of the most effective antifungal agent for overcoming the antifungal resistance is crucial. However, there are limited studies guiding the optimal dosage and duration of treatment for management of emergent antifungal resistance. Further studies are warranted to elucidate the optimal pharmacology of the current antifungal agents against resistant organisms and to advance the development of new antifungal agents.

Therapeutic Drug Monitoring and Genotypic Screening in the Clinical Use of Voriconazole

Voriconazole is an antifungal triazole that is the first line agent for treatment of invasive aspergillosis. It is metabolized by CYP2C19, CYP2C9, and CYP3A4 and demonstrates wide interpatient variability in serum concentrations. Polymorphisms in CYP2C19 contribute to variability in voriconazole pharmacokinetics. Here, evidence is examined for the use of voriconazole therapeutic drug monitoring (TDM) and the role of CYP2C19 genotyping in voriconazole dosing. The majority of studies exploring the impact of voriconazole TDM on efficacy and safety have found TDM to be beneficial. However, most of these studies are observational, with only one being a randomized controlled trial. High-volume multicenter randomized controlled trials of TDM are currently not available to support definitive guidelines. There is a significant relationship in healthy volunteers between CYP2C19 genotype and voriconazole pharmacokinetics, but this association is markedly less visible in actual patients. While CYP2C19 genotype data may explain variability of voriconazole serum levels, they alone are not sufficient to guide initial dosing. The timeliness of availability of CYP2C19 genotype data in treatment of individual patients also remains challenging. Additional studies are needed before implementation of CYP2C19 genotyping for voriconazole dosing into routine clinical care.

Voriconazole plasma concentrations in immunocompromised pediatric patients vary by CYP2C19 diplotypes

AIM

Our objective was to describe the association between voriconazole concentrations and CYP2C19 diplotypes in pediatric cancer patients, including children homozygous for the CYP2C19*17 gain-of-function allele.

MATERIALS & METHODS

A linear mixed effect model compared voriconazole dose-corrected trough concentrations (n = 142) among CYP2C19 diplotypes in 33 patients (aged 1-19 years). Voriconazole pharmacokinetics was described by a two-compartment model with Michaelis-Menten elimination.

RESULTS

Age (p = 0.05) and CYP2C19 diplotype (p = 0.002) were associated with voriconazole concentrations. CYP2C19*17 homozygotes never attained therapeutic concentrations, and had lower dose-corrected voriconazole concentrations (median 0.01 μg/ml/mg/kg; p = 0.02) than CYP2C19*1 homozygotes (median 0.07 μg/ml/mg/kg). Modeling indicates that higher doses may produce therapeutic concentrations in younger children and in those with a CYP2C19*17/*17 diplotype.

CONCLUSION

Younger age and the presence of CYP2C19 gain-of-function alleles were associated with subtherapeutic voriconazole concentrations. Starting doses based on age and CYP2C19 status could increase the number of patients achieving therapeutic voriconazole exposure.

Therapeutic drug monitoring for triazoles: A needs assessment review and recommendations from a Canadian perspective

Invasive fungal infections cause significant morbidity and mortality in patients with concomitant underlying immunosuppressive diseases. The recent addition of new triazoles to the antifungal armamentarium has allowed for extended-spectrum activity and flexibility of administration. Over the years, clinical use has raised concerns about the degree of drug exposure following standard approved drug dosing, questioning the need for therapeutic drug monitoring (TDM). Accordingly, the present guidelines focus on TDM of triazole antifungal agents. A review of the rationale for triazole TDM, the targeted patient populations and available laboratory methods, as well as practical recommendations based on current evidence from an extended literature review are provided in the present document.

Pharmacokinetics and safety of voriconazole intravenous-to-oral switch regimens in immunocompromised Japanese pediatric patients

The aim of this study was to investigate the pharmacokinetics, safety, and tolerability of voriconazole following intravenous-to-oral switch regimens used with immunocompromised Japanese pediatric subjects (age 2 to <15 years) at high risk for systemic fungal infection. Twenty-one patients received intravenous-to-oral switch regimens based on a recent population pharmacokinetic modeling; they were given 9 mg/kg of body weight followed by 8 mg/kg of intravenous (i.v.) voriconazole every 12 h (q12h), and 9 mg/kg (maximum, 350 mg) of oral voriconazole q12h (for patients age 2 to <12 or 12 to <15 years and <50 kg) or 6 mg/kg followed by 4 mg/kg of i.v. voriconazole q12h and 200 mg of oral voriconazole q12h (for patients age 12 to <15 years and ≥50 kg). The steady-state area under the curve over the 12-h dosing interval (AUC0-12,ss) was calculated using the noncompartmental method and compared with the predicted exposures in Western pediatric subjects based on the abovementioned modeling. The geometric mean (coefficient of variation) AUC0-12,ss values for the intravenous and oral regimens were 51.1 μg · h/ml (68%) and 45.8 μg·h/ml (90%), respectively; there was a high correlation between AUC0-12,ss and trough concentration. Although the average exposures were higher in the Japanese patients than those in the Western pediatric subjects, the overall voriconazole exposures were comparable between these two groups due to large interindividual variability. The exposures in the 2 cytochrome P450 2C19 poor metabolizers were among the highest. Voriconazole was well tolerated. The most common treatment-related adverse events were photophobia and abnormal hepatic function. These recommended doses derived from the modeling appear to be appropriate for Japanese pediatric patients, showing no additional safety risks compared to those with adult patients. (This study has been registered at ClinicalTrials.gov under registration no. NCT01383993.).

Invasive candidiasis and candidaemia in neonates and children: update on current guidelines

Invasive candidiasis (IC) and candidaemia are leading causes of infectious morbidity and mortality among immunocompromised paediatric patients and those admitted to intensive care units. Despite improvements in diagnosis, prevention and treatment, both mortality rates and the economic burden of disease still remain high. To address this issue, several international societies and organisations have proposed guidelines for the management of IC/candidaemia in both neonates and children. In this article, we review current recommendations of the Infectious Diseases Society of America, the European Conference on Infection in Leukaemia, the European Society of Clinical Microbiology and Infectious Diseases and the German Speaking Mycological Society/Paul-Ehrlich Society for Chemotherapy for the management and prevention of IC/candidaemia in children and neonates.

Phototoxic dermatoses in pediatric BMT patients receiving voriconazole

We investigated the incidence of phototoxic skin reactions in pediatric BMT recipients treated with voriconazole. Nine out of 40 patients (22.5%), all Caucasian, developed skin lesions in sun-exposed distributions. Dermatologic findings included sunburn-like erythema, pseudo-porphyria, linear papulovesicular lesions, severe erosive cheilitis, dermatoheliosis and lentigines. Patients were treated with sun avoidance, high-potency sunscreens, and topical steroids with significant improvement in all cases. Prolonged voriconazole use requires close monitoring for chronic skin toxicities. Long-term risks including the risk of skin cancer need to be investigated.

Pharmacokinetics and pharmacodynamics of antifungals in children: clinical implications

Invasive fungal disease (IFD) remains life threatening in premature infants and immunocompromised children despite the recent development of new antifungal agents. Optimal dosing of antifungals is one of the few factors clinicians can control to improve outcomes of IFD. However, dosing in children cannot be extrapolated from adult data because IFD pathophysiology, immune response, and drug disposition differ from adults. We critically examined the literature on pharmacokinetics (PK) and pharmacodynamics (PD) of antifungal agents and highlight recent developments in treating pediatric IFD. To match adult exposure in pediatric patients, dosing adjustment is necessary for almost all antifungals. In young infants, the maturation of renal and metabolic functions occurs rapidly and can significantly influence drug exposure. Fluconazole clearance doubles from birth to 28 days of life and, beyond the neonatal period, agents such as fluconazole, voriconazole, and micafungin require higher dosing than in adults because of faster clearance in children. As a result, dosing recommendations are specific to bracketed ranges of age. PD principles of antifungals mostly rely on in vitro and in vivo models but very few PD studies specifically address IFD in children. The exposure-response relationship may differ in younger children compared with adults, especially in infants with invasive candidiasis who are at higher risk of disseminated disease and meningoencephalitis, and by extension severe neurodevelopmental impairment. Micafungin is the only antifungal agent for which a specific target of exposure was proposed based on a neonatal hematogenous Candida meningoencephalitis animal model. In this review, we found that pediatric data on drug disposition of newer triazoles and echinocandins are lacking, dosing of older antifungals such as fluconazole and amphotericin B products still need optimization in young infants, and that target PK/PD indices need to be clinically validated for almost all antifungals in children. A better understanding of age-specific PK and PD of new antifungals in infants and children will help improve clinical outcomes of IFD by informing dosing and identifying future research areas.

Antifungal therapy in children: an update

Invasive fungal infections are a common problem in children affected by primary or secondary immunodeficiencies. Thanks to an increased knowledge about their mechanisms of action and their pharmacokinetic and toxicity profiles, the use of these drugs in common and uncommon invasive infections in immunocompromised children has improved over the last decades. Choosing the most appropriate antifungal drug is a serious challenge for any clinician, also considering that, in most cases, therapy has to be started before cultures are available, the choice being driven by clinical symptoms and statistical criteria only. In this study, we performed a systematic review of literature, providing antifungal treatment recommendations for paediatric patients which can help clinicians find the most suitable treatment for each specific case. Principal antifungal drugs-ranging from first-generation antimycotics to the latest molecules-are classified according to their targets, and of each group, the pharmacokinetic profile, clinical indications and side effects are extensively described.

Newer antifungal agents

PURPOSE OF REVIEW

In recent years there has been an evolution of a better understanding of the pharmacology and clinical indications of existing antifungal agents and also the development of new broad-spectrum triazoles and a newer class of antifungal agents, the echinocandins. The availability of these agents has broadened the therapeutic options of invasive fungal disease among children and consequently antifungal therapy has become increasingly complex.

RECENT FINDINGS

Adoption of adult guidelines' recommendations has been used to guide pediatric treatment as specific pediatric data were often lacking. This approach has not always selected the most appropriate therapy for newborns or young infants, as the under-dosage of voriconazole based on adult data revealed. Therefore, a detailed understanding of the available antifungal agents in children is crucial for the successful treatment of these serious infections.

SUMMARY

In this review we summarize the main findings regarding antifungal treatment among children that have been recently published, focusing on the pharmacology and pediatric use of newer antifungal agents.

Importance of voriconazole therapeutic drug monitoring in pediatric cancer patients with invasive aspergillosis

BACKGROUND

Voriconazole is the drug of choice for invasive aspergillosis (IA) and drug levels are influenced by interactions with other drugs and genetic predisposition. We performed a retrospective analysis of voriconazole drug levels and investigated the adequacy of drug levels in pediatric cancer patients and hematopoietic cell transplant (HCT) recipients with IA.

PROCEDURE

Trough serum concentrations of voriconazole in patients younger than 19 years during a 30-month period were analyzed. The therapeutic range was determined as 1-6 µg/ml.

RESULTS

A total of 193 voriconazole measurements at steady-state [86 on intravenous (IV) and 107 on oral (PO) doses] were obtained from 27 patients (median age 12.2 years). On the first monitoring, 19 patients (70.4%) achieved the therapeutic range. However, only 10 patients (37.0%) achieved the therapeutic range on second monitoring. Sixty-four percent of the total measurements were within the therapeutic range: 66.3% of IV and 61.7% of PO. A significant correlation between oral doses and trough levels of voriconazole was observed in patients ≤6 years old (Spearman's rank correlation coefficient = 0.4819, P = 0.027). Patients aged ≤6 years needed a significantly higher median dose of PO voriconazole to maintain therapeutic trough levels compared to older patient groups (8.9 vs. 4.2 mg/kg/dose, P < 0.001). Voriconazole level <1 µg/ml was more frequently observed in patients with treatment failure at week 6 of voriconazole therapy (failure vs. success, 42.1% vs. 19.7%; P = 0.012).

CONCLUSIONS

Serum concentrations of voriconazole in children were variable, depending on the patient's age and route of administration. Continuous and careful drug level monitoring should be performed.

Efficacy of voriconazole in a murine model of acute Trypanosoma cruzi infection

OBJECTIVES

Antifungal triazole derivatives have been studied as possible alternatives for the treatment of Chagas' disease. Voriconazole has demonstrated in vitro activity against Trypanosoma cruzi, but its efficacy in vivo has not yet been tested. We aimed to determine the effect of voriconazole in a murine model of acute T. cruzi infection.

METHODS

Treatment efficacy was evaluated by comparing parasitaemia, mortality and organ involvement (by histological examination) of infected mice.

RESULTS

Treatment with voriconazole significantly lowered parasitaemia and mortality compared with controls, reduced the percentage of mice with amastigote nests in heart and skeletal muscle and moderately decreased myocardial inflammation.

CONCLUSIONS

Our findings support the potential of voriconazole for the treatment of acute Chagas' disease and motivate future animal studies using varying doses and treatment schemes. Further evaluation of voriconazole for clinical use in human Chagas' patients is warranted.

Highly variable plasma concentrations of voriconazole in pediatric hematopoietic stem cell transplantation patients

Invasive fungal infections are of great concern in pediatric hematopoietic stem cell transplantation (HSCT) recipients. Voriconazole is usually the drug of first choice for treating or preventing invasive aspergillosis. Optimum trough levels (C(trough)s) are between 1 and 5 mg/liter. It is unclear whether these levels are reached with currently advised pediatric dosing schedules. Between 2007 and 2011, 11 patients <2 years of age, 31 between 2 and 12 years, and 20 between 12 and 20 years were (prophylactically or therapeutically) treated with voriconazole in the HSCT unit of UMC Utrecht. For children <2 years of age, the dosage recommended for 2 to 12 years was used. In 34% of children who started with the recommended dose, an adequate C(trough) was reached irrespective of age or administration route. After therapeutic drug monitoring (TDM)-based dose adjustments, adequate C(trough)s were reached in 80% of the patients at median doses of 31.5 (age, <2 years), 16 (age, 2 to 12 years), and 9.4 mg/kg of body weight/day (age, >12 years) (P = 0.034). The intrapatient variability in C(trough) ranged between 1 and 238%. Voriconazole was discontinued in six patients due to toxicity. These patients had a median C(trough) of 0.5 mg/liter at the initial dose (ranging from 0.5 to 2.6 mg/liter), and a medium maximal concentration of 4 mg/liter was reached. Inter- and intrapatient variability is a major concern in voriconazole treatment and necessitates therapeutic drug monitoring of dosing, especially in young children.

Monitoring of voriconazole plasma concentrations in immunocompromised paediatric patients

OBJECTIVES

Voriconazole is approved for management of invasive fungal diseases (IFDs) in paediatric patients. We analysed plasma trough concentrations and explored their association with endpoints of antifungal therapy.

PATIENTS AND METHODS

The cohort included 74 immunocompromised patients (0.2-18 years of age) who received 101 courses of voriconazole for possible (7) and probable/proven (13) IFDs, as prophylaxis (79) or empirical therapy (2). Voriconazole was given intravenously (4), intravenously and orally (15) and orally (82) at recommended dosages until intolerance or maximum efficacy. IFDs and outcomes were assessed by EORTC/MSG consensus criteria.

RESULTS

Voriconazole was administered at a median maintenance dosage of 4.8 mg/kg twice daily (range 2.2-17.4) for a median of 40 days (range 6-1002). Trough plasma concentrations at steady state (251 samples; 3.4 ± 4.3/patient) ranged from <0.2 to 14.9 mg/L with high intra- and inter-individual variability and no apparent relationship to dose (P = 0.074, ANOVA). Of the samples 22%, 42% and 58% had voriconazole concentrations <0.2, ≤0.5 and ≤1.0 mg/L, respectively. Adverse events (AEs) occurred in 77/101 (76.2%) courses and were mostly grade I or II. Ten courses (9.9%) were discontinued due to AEs. Treatment success was observed in 8/20 patients (40%) with IFDs, and in 67/81 courses (82.7%) of empirical therapy/prophylaxis. There were no consistent correlations between dose, trough concentrations and laboratory/clinical AEs or treatment response, and proposed threshold values were not discriminative.

CONCLUSIONS

Voriconazole had acceptable safety and useful efficacy in the management of paediatric IFDs. Pharmacokinetic variability was high and no predictable dose-concentration-effect relationships were observed.

Therapeutic monitoring of voriconazole in children less than three years of age: a case report and summary of voriconazole concentrations for ten children

Voriconazole is the treatment of choice for invasive aspergillosis and its use is increasing in pediatrics. Minimal pharmacokinetic data exist in young children. We report voriconazole concentrations for 10 children <3 years of age and pharmacokinetic parameters for 1 infant who had therapeutic drug monitoring performed. Trough concentrations were unpredictable based on dose, highlighting the need to follow values during therapy.

Integrated population pharmacokinetic analysis of voriconazole in children, adolescents, and adults

To further optimize the voriconazole dosing in the pediatric population, a population pharmacokinetic analysis was conducted on pooled data from 112 immunocompromised children (2 to <12 years), 26 immunocompromised adolescents (12 to <17 years), and 35 healthy adults. Different maintenance doses (i.e., 3, 4, 6, 7, and 8 mg/kg of body weight intravenously [i.v.] every 12 h [q12h]; 4 mg/kg, 6 mg/kg, and 200 mg orally q12h) were evaluated in these children. The adult dosing regimens (6 mg/kg i.v. q12h on day 1, followed by 4 mg/kg i.v. q12h, and 300 mg orally q12h) were evaluated in the adolescents. A two-compartment model with first-order absorption and mixed linear and nonlinear (Michaelis-Menten) elimination adequately described the voriconazole data. Larger interindividual variability was observed in pediatric subjects than in adults. Deterministic simulations based on individual parameter estimates from the final model revealed the following. The predicted total exposure (area under the concentration-time curve from 0 to 12 h [AUC(0-12)]) in children following a 9-mg/kg i.v. loading dose was comparable to that in adults following a 6-mg/kg i.v. loading dose. The predicted AUC(0-12)s in children following 4 and 8 mg/kg i.v. q12h were comparable to those in adults following 3 and 4 mg/kg i.v. q12h, respectively. The predicted AUC(0-12) in children following 9 mg/kg (maximum, 350 mg) orally q12h was comparable to that in adults following 200 mg orally q12h. To achieve voriconazole exposures comparable to those of adults, dosing in 12- to 14-year-old adolescents depends on their weight: they should be dosed like children if their weight is <50 kg and dosed like adults if their weight is ≥ 50 kg. Other adolescents should be dosed like adults.

The use of antifungal therapy in neonatal intensive care

Invasive fungal infections remain a significant cause of infection-related mortality and morbidity in preterm infants. Central nervous system involvement is the hallmark of neonatal candidiasis, differentiating the disease's impact on young infants from that among all other patient populations. Over the past decade, the number of antifungal agents in development has grown, but most are not labeled for use in newborns. We summarize the findings of several antifungal studies that have been completed to date, emphasizing those including infant populations. We conclude that more studies are required for antifungals to be used safely and effectively in infants.

Safety and efficacy of liposomal amphotericin B for the empirical therapy of invasive fungal infections in immunocompromised patients

Liposomal amphotericin B is a “true” liposomal formulation of amphotericin B with greatly reduced nephrotoxicity and minimal infusion-related toxicity. This broad spectrum polyene is well tolerated and effective against most invasive fungal infections. In view of the current limitations on diagnostic capability of invasive fungal infections, most clinicians are often compelled to use antifungal drugs in an empiric manner; liposomal amphotericin B continues to play an important role in the empiric management of invasive fungal infections, despite the recent availability of several other drugs in the azole and echinocandin classes.

Voriconazole serum levels measured by high-performance liquid chromatography: a monocentric study in treated patients

In this study we present the results of a therapeutic drug monitoring retrospective analysis involving 14 patients with several underlying diseases who were receiving voriconazole for the treatment of fungal infections. A simple high performance liquid chromatography assay with ultraviolet detection was used in the drug monitoring. We report here that serum concentrations were highly variable and unpredictable in most patients. We also found that lack of response was more frequent in patients with levels persistently lower than 1 mg/l. The number of samples with voriconazole concentrations below 1 mg/l was significantly higher in patients who exhibited therapeutic failures (88% versus 27%; P < 0.001). In addition, the period of time in which voriconazole concentrations were maintained below 1 mg/l was slightly higher in patients in the failure group. We suggest that serum concentration should be individually quantified for patients receiving voriconazole therapy. Further prospective studies are needed to clarify the potential benefit of the individualization of treatment.

Comparison of pharmacokinetics and safety of voriconazole intravenous-to-oral switch in immunocompromised children and healthy adults

Voriconazole pharmacokinetics are not well characterized in children despite prior studies. To assess the appropriate pediatric dosing, a study was conducted in 40 immunocompromised children aged 2 to <12 years to evaluate the pharmacokinetics and safety of voriconazole following intravenous (IV)-to-oral (PO) switch regimens based on a previous population pharmacokinetic modeling: 7 mg/kg IV every 12 h (q12h) and 200 mg PO q12h. Area under the curve over the 12-h dosing interval (AUC(0-12)) was calculated using the noncompartmental method and compared to that for adults receiving approved dosing regimens (6 → 4 mg/kg IV q12h, 200 mg PO q12h). On average, the AUC(0-12) in children receiving 7 mg/kg IV q12h on day 1 and at IV steady state were 7.85 and 21.4 μg · h/ml, respectively, and approximately 44% and 40% lower, respectively, than those for adults at 6 → 4 mg/kg IV q12h. Large intersubject variability was observed. At steady state during oral treatment (200 mg q12h), children had higher average exposure than adults, with much larger intersubject variability. The exposure achieved with oral dosing in children tended to decrease as weight and age increased. The most common treatment-related adverse events were transient elevated liver function tests. No clear threshold of voriconazole exposure was identified that would predict the occurrence of treatment-related hepatic events. Overall, voriconazole IV doses higher than 7 mg/kg are needed in children to closely match adult exposures, and a weight-based oral dose may be more appropriate for children than a fixed dose. Safety of voriconazole in children was consistent with the known safety profile of voriconazole.

Comparison of pharmacokinetics and safety of voriconazole intravenous-to-oral switch in immunocompromised adolescents and healthy adults

The current voriconazole dosing recommendation in adolescents is based on limited efficacy and pharmacokinetic data. To confirm the appropriateness of dosing adolescents like adults, a pharmacokinetic study was conducted in 26 immunocompromised adolescents aged 12 to <17 years following intravenous (IV) voriconazole to oral switch regimens: 6 mg/kg IV every 12 h (q12h) on day 1 followed by 4 mg/kg IV q12h, then switched to 300 mg orally q12h. Area under the curve over a 12-hour dosing interval (AUC(0-12)) was calculated using a noncompartmental method and compared to the value for adults receiving the same dosing regimens. On average, the AUC(0-12) in adolescents after the first loading dose on day 1 and at steady state during IV treatment were 9.14 and 22.4 μg·h/ml, respectively (approximately 34% and 36% lower, respectively, than values for adults). At steady state during oral treatment, adolescents also had lower average exposure than adults (16.7 versus 34.0 μg·h/ml). Larger intersubject variability was observed in adolescents than in adults. There was a slight trend for some young adolescents with low body weight to have lower voriconazole exposure. It is likely that these young adolescents may metabolize voriconazole more similarly to children than to adults. Overall, with the same dosing regimens, voriconazole exposures in the majority of adolescents were comparable to those in adults. The young adolescents with low body weight during the transitioning period from childhood to adolescence (e.g., 12 to 14 years old) may need to receive higher doses to match the adult exposures. Safety of voriconazole in adolescents was consistent with the known safety profile of voriconazole.

Emergent Complications in the Pediatric Hematopoietic Stem Cell Transplant Patient

Hematopoietic cell transplantation is the only potentially curative option for a variety of pediatric malignant and nonmalignant disorders. Despite advances in transplantation biology and immunology as well as in posttransplant management that have contributed to improved survival and decreased transplant-related mortality, hematopoietic cell transplantation does not come without significant risk of complications. When patients who have undergone hematopoietic cell transplantation present to the emergency department, it is important to consider a variety of therapy-related complications to optimize management and outcome. In this article, we use clinical cases to highlight some of the more common emergent complications after hematopoietic cell transplantation.

Current concepts in antifungal pharmacology

The introduction of new antifungal agents (eg, echinocandins, second-generation triazoles) in the past decade has transformed the management of invasive mycoses to the point that drug toxicity is no longer the major limiting factor in treatment. Yet, many of these newer antifungal agents have important limitations in their spectrum of activity, pharmacokinetics, and unique predisposition for pharmacokinetic drug-drug interactions and unusual toxicities associated with long-term use. This article reviews key pharmacological aspects of systemic antifungal agents as well as evolving strategies, such as pharmacokinetic-pharmacodynamic optimization and therapeutic drug monitoring, to improve the safety and efficacy of systemic antifungal therapy.