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

Voriconazole therapeutic drug monitoring including analysis of CYP2C19 phenotype in immunocompromised pediatric patients with invasive fungal infections

PURPOSE

Therapeutic drug monitoring (TDM) of voriconazole (VCZ) should be mandatory for all pediatric patients with invasive fungal infections (IFIs). The narrow therapeutic index, inter-individual variability in VCZ pharmacokinetics, and genetic polymorphisms cause achieving therapeutic concentration during therapy to be challenging in this population.

METHODS

The study included 44 children suffering from IFIs treated with VCZ. Trough concentrations (Ctrough) of VCZ ware determined by the HPLC-FLD method. Identification of the CYP2C19*2 and CYP2C19*17 genetic polymorphisms was performed by PCR-RFLP. The correlation between polymorphisms and VCZ Ctrough was analyzed. Moreover, the effect of factors such as dose, age, sex, route of administration, and drug interactions was investigated.

RESULTS

VCZ was administered orally and intravenously at a median maintenance dosage of 14.7 mg/kg/day for a median of 10 days. The VCZ Ctrough was highly variable and ranged from 0.1 to 6.8 mg/L. Only 45% of children reached the therapeutic range. There was no significant association between Ctrough and dosage, age, sex, route of administration, and concomitant medications. The frequencies of variant phenotype normal (NM), intermediate (IM), rapid (RM) and ultrarapid metabolizers (UM) were 41%, 18%, 28%, and 13%, respectively. Ctrough of VCZ were significantly higher in NM and IM groups compared with RM, and UM groups.

CONCLUSION

The Ctrough of VCZ is characterized by inter-individual variability and a low rate of patients reaching the therapeutic range. The significant association exists in children between VCZ Ctrough and CYPC19 phenotype. The combination of repeated TDM and genotyping is necessary to ensure effective treatment.

Associated factors with voriconazole plasma concentration: a systematic review and meta-analysis

Background: Voriconazole plasma concentration exhibits significant variability and maintaining it within the therapeutic range is the key to enhancing its efficacy. We conducted a systematic review and meta-analysis to estimate the prevalence of patients achieving the therapeutic range of plasma voriconazole concentration and identify associated factors. Methods: Eligible studies were identified through the PubMed, Embase, Cochrane Library, and Web of Science databases from their inception until 18 November 2023. We conducted a meta-analysis using a random-effects model to determine the prevalence of patients who reached the therapeutic plasma voriconazole concentration range. Factors associated with plasma voriconazole concentration were summarized from the included studies. Results: Of the 60 eligible studies, 52 reported the prevalence of patients reaching the therapeutic range, while 20 performed multiple linear regression analyses. The pooled prevalence who achieved the therapeutic range was 56% (95% CI: 50%-63%) in studies without dose adjustment patients. The pooled prevalence of adult patients was 61% (95% CI: 56%-65%), and the pooled prevalence of children patients was 55% (95% CI: 50%-60%) The study identified, in the children population, several factors associated with plasma voriconazole concentration, including age (coefficient 0.08, 95% CI: 0.01 to 0.14), albumin (-0.05 95% CI: -0.09 to -0.01), in the adult population, some factors related to voriconazole plasma concentration, including omeprazole (1.37, 95% CI 0.82 to 1.92), pantoprazole (1.11, 95% CI: 0.17-2.04), methylprednisolone (-1.75, 95% CI: -2.21 to -1.30), and dexamethasone (-1.45, 95% CI: -2.07 to -0.83). Conclusion: The analysis revealed that only approximately half of the patients reached the plasma voriconazole concentration therapeutic range without dose adjustments and the pooled prevalence of adult patients reaching the therapeutic range is higher than that of children. Therapeutic drug monitoring is crucial in the administration of voriconazole, especially in the children population. Particular attention may be paid to age, albumin levels in children, and the use of omeprazole, pantoprazole, dexamethasone and methylprednisolone in adults. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023483728.

Clinical application of voriconazole in pediatric patients: a systematic review

The purpose of this study was to review the literature on the clinical use of voriconazole (VRC) in pediatric patients. MEDLINE, Embase, PubMed, Web of Science, and Cochrane Library were searched from January 1, 2000, to August 15, 2023 for relevant clinical studies on VRC use in pediatric patients. Data were collected based on inclusion and exclusion criteria, and a systematic review was performed on recent research related to the use of VRC in pediatric patients. This systematic review included a total of 35 observational studies among which there were 16 studies investigating factors influencing VRC plasma trough concentrations (Ctrough) in pediatric patients, 14 studies exploring VRC maintenance doses required to achieve target range of Ctrough, and 11 studies focusing on population pharmacokinetic (PPK) research of VRC in pediatric patients. Our study found that the Ctrough of VRC were influenced by both genetic and non-genetic factors. The optimal dosing of VRC was correlated with age in pediatric patients, and younger children usually required higher VRC doses to achieve target Ctrough compared to older children. Establishing a PPK model for VRC can assist in achieving more precise individualized dosing in children.

Therapeutic Drug Monitoring of Voriconazole in Critically Ill Pediatric Patients: A Single-Center Retrospective Study

BACKGROUND AND OBJECTIVE

Voriconazole pharmacokinetics are highly variable in pediatric patients, and the optimal dosage has yet to be determined. The purpose of this study was to describe voriconazole pharmacokinetic and pharmacodynamic targets achieved and evaluate the efficacy and safety of voriconazole for critically ill pediatrics.

METHODS

This is a single-center retrospective study conducted at a pediatric intensive care unit at a tertiary/quaternary hospital. Pediatrics admitted to the pediatric intensive care unit and who received voriconazole for a proven or suspected fungal infection with at least one measured trough concentration were included. The primary outcomes included the percentage of pediatric patients who achieved the pharmacokinetic and pharmacodynamic targets. Secondary outcomes included assessing the correlation between voriconazole trough concentrations and clinical/microbiological outcomes. All statistical analyses were performed using the R statistical software and Microsoft Excel. Multiple logistic regression was used to assess the predictors of both clinical and microbiologic cures. Multiple linear regression was used to determine significant factors associated with trough concentrations.

RESULTS

A total of 129 voriconazole trough concentrations were measured from 71 participants at steady state after at least three doses of voriconazole. The mean (± standard deviation) of the first and second trough concentrations were 2.9 (4.2) and 2.3 (3.3) mg/L, respectively. Among the first trough concentrations, only 33.8% were within the therapeutic range (1-5 mg/L), 46.5% were below the therapeutic range, and 19.7% were above the therapeutic range. A clinical cure occurred in 78% of patients, while a microbiologic cure occurred in 80% of patients.

CONCLUSIONS

Voriconazole trough concentrations vary widely in critically ill pediatric patients and only a third of the patients achieved therapeutic concentrations with initial doses.

Voriconazole plasma concentrations and dosing in paediatric patients below 24 months of age

Voriconazole (VCZ) is an important first-line option for management of invasive fungal diseases and approved in paediatric patients ≥24 months at distinct dosing schedules that consider different developmental stages. Information on dosing and exposures in children <24 months of age is scarce. Here we report our experience in children <24 months who received VCZ due to the lack of alternative treatment options. This retrospective analysis includes 50 distinct treatment episodes in 17 immunocompromised children aged between 3 and <24 months, who received VCZ between 2004 and 2022 as prophylaxis (14 patients; 47 episodes) or as empirical treatment (3 patients; 3 episodes) by mouth (46 episodes) or intravenously (4 episodes) based on contraindications, intolerance or lack of alternative options. Trough concentrations were measured as clinically indicated, and tolerability was assessed based on hepatic function parameters and discontinuations due to adverse events (AEs). VCZ was administered for a median duration of 10 days (range: 1-138). Intravenous doses ranged from 4.9 to 7.0 mg/kg (median: 6.5) twice daily, and oral doses from 3.8 to 29 mg/kg (median: 9.5) twice daily, respectively. The median trough concentration was 0.63 mg/L (range: 0.01-16.2; 38 samples). Only 34.2% of samples were in the recommended target range of 1-6 mg/L; 57.9% had lower and 7.9% higher trough concentrations. Hepatic function parameters analysed at baseline, during treatment and at end of treatment did not show significant changes during VCZ treatment. There was no correlation between dose and exposure or hepatic function parameters. In three episodes, VCZ was discontinued due to an AE (6%; three patients). In conclusion, this retrospective analysis reveals no signal for increased toxicity in paediatric patients <24 months of age. Empirical dosing resulted in mostly subtherapeutic exposures which emphasises the need for more systematic study of the pharmacokinetics of VCZ in this age group.

Population pharmacokinetics of voriconazole and the role of CYP2C19 genotype on treatment optimization in pediatric patients

The aim of this study was to evaluate factors that impact on voriconazole (VRC) population pharmacokinetic (PPK) parameters and explore the optimal dosing regimen for different CYP2C19 genotypes in Chinese paediatric patients. PPK analysis was used to identify the factors contributing to the variability in VRC plasma trough concentrations. A total of 210 VRC trough concentrations from 91 paediatric patients were included in the study. The median VRC trough concentration was 1.23 mg/L (range, 0.02 to 8.58 mg/L). At the measurement of all the trough concentrations, the target range (1.0~5.5 mg/L) was achieved in 52.9% of the patients, while subtherapeutic and supratherapeutic concentrations were obtained in 40.9% and 6.2% of patients, respectively. VRC trough concentrations were adjusted for dose (Ctrough/D), with normal metabolizers (NMs) and intermediate metabolizers (IMs) having significantly lower levels than poor metabolizers (PMs) (PN-P < 0.001, PI-P = 0.039). A one-compartment model with first-order absorption and elimination was suitable to describe the VRC pharmacokinetic characteristics. The final model of VRC PPK analysis contained CYP2C19 phenotype as a significant covariate for clearance. Dose simulations suggested that a maintenance dose of 9 mg/kg orally or 8 mg/kg intravenously twice daily was appropriate for NMs to achieve the target concentration. A maintenance dose of 9 mg/kg orally or 5 mg/kg intravenously twice daily was appropriate for IMs. Meanwhile, PMs could use lower maintenance dose and an oral dose of 6 mg/kg twice daily or an intravenous dose of 5mg/kg twice daily was appropriate. To increase the probability of achieving the therapeutic range and improving efficacy, CYP2C19 phenotype can be used to predict VRC trough concentrations and guide dose adjustments in Chinese pediatric patients.

Therapeutic drug monitoring of voriconazole and CYP2C19 phenotype for dose optimization in paediatric patients

PURPOSE

The objective of this study was to evaluate factors influencing voriconazole (VRC) plasma trough concentrations and provide research data for optimizing VRC dosing in Chinese paediatric patients.

METHODS

Medical records of inpatients were reviewed retrospectively. Multivariate linear regression analysis was used to identify the factors contributing to the variability of VRC plasma trough concentrations.

RESULTS

A total of 250 VRC plasma trough concentrations from 131 paediatric patients were included in the analysis. The median VRC plasma trough concentration was 1.28 mg·L-1 (range, 0.02 to 9.69 mg·L-1). The target range was achieved in 51.6% of patients, while subtherapeutic and supratherapeutic concentrations were obtained in 40.4% and 8.0% of paediatric patients, respectively. The most commonly identified cytochrome P450 2C19 (CYP2C19) phenotype was intermediate metabolizers (IMs) (48.9%), followed by normal metabolizers (NMs) (40.5%) and poor metabolizers (PMs) (10.7%), but no ultrarapid metabolizers (UMs) were observed in our study. VRC plasma trough concentrations adjusted for dose (Cmin/D) were significantly lower in both NMs and IMs compared to PMs (PN-P < 0.001 and PI-P = 0.010, respectively). The dosage of VRC required to achieve the therapeutic range was related to age, with children aged < 6 years needing a significantly higher oral dose of VRC. The oral and intravenous maintenance doses needed to reach the therapeutic range were significantly lower than the recommended maintenance dose (P < 0.001, P < 0.001). Factors such as CYP2C19 polymorphisms, the combination of omeprazole, levels of albumin and alanine aminotransferase, were found to affect VRC exposure and explained some of the variability.

CONCLUSIONS

The VRC plasma trough concentration is significantly influenced by the CYP2C19 phenotype. The recommended maintenance dose for pediatric patients may not be appropriate for Chinese patients. To increase the probability of achieving the therapeutic range for VRC plasma trough concentration, the administration of VRC should consider the age of paediatric patients and the presence of CYP2C19 polymorphisms.

Challenges in the Treatment of Invasive Aspergillosis in Immunocompromised Children

Invasive aspergillosis (IA) is associated with significant morbidity and mortality. Voriconazole remains the drug of choice for the treatment of IA in children; however, the complex kinetics of voriconazole in children make dosing challenging and therapeutic drug monitoring (TDM) essential for treatment success. The overarching goal of this review is to discuss the role of voriconazole, posaconazole, isavuconazole, liposomal amphotericin B, echinocandins, and combination antifungal therapy for the treatment of IA in children. We also provide a detailed discussion of antifungal TDM in children.

Predictive Value of C-Reactive Protein and Albumin for Temporal Within-Individual Pharmacokinetic Variability of Voriconazole in Pediatric Hematopoietic Cell Transplant Patients

Voriconazole is a widely used antifungal agent in immunocompromised patients, but its utility is limited by its variable exposure and narrow therapeutic index. Population pharmacokinetic (PK) models have been used to characterize voriconazole PK and derive individualized dosing regimens. However, determinants of temporal within-patient variability of voriconazole PK were not well-established. We aimed to characterize temporal variability of voriconazole PK within individuals and identify predictive clinical factors. This study was conducted as a part of a single-institution, phase I study of intravenous voriconazole in children undergoing HCT (NCT02227797). We analyzed voriconazole PK study data collected at week 1 and again at week 2 after the start of voriconazole therapy in 59 pediatric HCT patients (age <21 years). Population PK analysis using nonlinear mixed effect modeling was performed to analyze temporal within-individual variability of voriconazole PK by incorporating a between-occasion variability term in the model. A two-compartment linear elimination model incorporating body weight and CYP2C19 phenotype described the data. Ratio of individual voriconazole clearance between weeks 1 to 2 ranged from 0.11 to 3.3 (-9.1 to +3.3-fold change). Incorporation of covariate effects by serum C-reactive protein (CRP) and albumin levels decreased between-occasion variability of clearance (coefficient of variation: from 59.5% to 41.2%) and improved the model fit (p<0.05). As significant covariates on voriconazole PK, CRP and albumin concentrations may potentially serve as useful biomarkers as part of therapeutic drug monitoring. This article is protected by copyright. All rights reserved.

A Large Sample Retrospective Study on the Distinction of Voriconazole Concentration in Asian Patients from Different Clinical Departments

Voriconazole (VRZ) is widely used to prevent and treat invasive fungal infections; however, there are a few studies examining the variability and influencing the factors of VRZ plasma concentrations across different clinical departments. This study aimed to evaluate distinction of VRZ concentrations in different clinical departments and provide a reference for its reasonable use. From 1 May 2014 to 31 December 2020, VRZ standard rates and factors affecting the VRZ trough concentration were analyzed, and a multiple linear regression model was constructed. The standard rates of VRZ in most departments were above 60%. A total of 676 patients with 1212 VRZ trough concentrations using a dosing regimen of 200 mg q12h from seven departments were enrolled in the correlation analysis. The concentration distribution varied significantly among different departments (p < 0.001). Fifteen factors, including department, CYP2C19 phenotype, and gender, correlated with VRZ concentration. A multiple linear regression model was established as follows: VRZ trough concentration = 5.195 + 0.049 × age + 0.007 × alanine aminotransferase + 0.010 × total bilirubin − 0.100 × albumin − 0.004 × gamma-glutamyl transferase. According to these indexes, we can predict possible changes in VRZ trough concentration and adjust its dosage precisely and individually.

Recent Advances in Therapeutic Drug Monitoring of Voriconazole, Mycophenolic Acid, and Vancomycin: A Literature Review of Pediatric Studies

The review includes studies dated 2011-2021 presenting the newest information on voriconazole (VCZ), mycophenolic acid (MPA), and vancomycin (VAN) therapeutic drug monitoring (TDM) in children. The need of TDM in pediatric patients has been emphasized by providing the information on the differences in the drugs pharmacokinetics. TDM of VCZ should be mandatory for all pediatric patients with invasive fungal infections (IFIs). Wide inter- and intrapatient variability in VCZ pharmacokinetics cause achieving and maintaining therapeutic concentration during therapy challenging in this population. Demonstrated studies showed, in most cases, VCZ plasma concentrations to be subtherapeutic, despite the updated dosages recommendations. Only repeated TDM can predict drug exposure and individualizing dosing in antifungal therapy in children. In children treated with mycophenolate mofetil (MMF), similarly as in adult patients, the role of TDM for MMF active form, MPA, has not been well established and is undergoing continued debate. Studies on the MPA TDM have been carried out in children after renal transplantation, other organ transplantation such as heart, liver, or intestine, in children after hematopoietic stem cell transplantation or cord blood transplantation, and in children with lupus, nephrotic syndrome, Henoch-Schönlein purpura, and other autoimmune diseases. MPA TDM is based on the area under the concentration-time curve; however, the proposed values differ according to the treatment indication, and other approaches such as pharmacodynamic and pharmacogenetic biomarkers have been proposed. VAN is a bactericidal agent that requires TDM to prevent an acute kidney disease. The particular group of patients is the pediatric one. For this group, the general recommendations of the dosing may not be valid due to the change of the elimination rate and volume of distribution between the subjects. The other factor is the variability among patients that concerns the free fraction of the drug. It may be caused by both the patients' population and sample preconditioning. Although VCZ, MMF, and VAN have been applied in pediatric patients for many years, there are still few issues to be solve regarding TDM of these drugs to ensure safe and effective treatment. Except for pharmacokinetic approach, pharmacodynamics and pharmacogenetics have been more often proposed for TDM.

Opportunities for Antimicrobial Stewardship Among Pediatric Patients Prescribed Combination Antifungal Therapy

OBJECTIVE

Combination antifungal therapy (CAF) may be prescribed to treat invasive fungal infections (IFIs). Data on the incidence of CAF among the pediatric population are limited. Antimicrobial stewardship for CAF includes therapeutic drug monitoring (TDM) and monitoring for adverse events. Primary outcome was to determine the incidence of CAF prescribed for documented proven, probable, and possible IFI. Secondary outcomes were to determine initial dose of antifungal therapy, determine incidence of adverse events, and evaluate our practice of TDM.

METHODS

Medical charts of patients who received CAF for proven, probable, or possible IFI within 6 years were reviewed. Patients age ≤18 years, prescribed CAF (defined as a second antifungal therapy started ≤72 hours of initial antifungal therapy) for at least 72 hours, and with normal liver function test results were included.

RESULTS

57 patients received CAF for 72 separate episodes: 35 episodes were proven IFI, 11 were probable IFI, and 26 were possible IFI. Initial dose of antifungal therapy varied, and 29.1% received a loading dose. A total of 10 patients experienced 14 adverse events that were related to antifungal therapy. In 63.8% of CAF episodes, TDM was conducted. Target antifungal concentrations were documented for 10 CAF episodes. Reason for discontinued of CAF was documented for 35 episodes. Of these episodes, 74% were discontinued after therapeutic antifungal concentrations were achieved.

CONCLUSIONS

There are opportunities for antimicrobial stewardship interventions in the method of TDM and monitoring for adverse events that could aid in management of CAF.

Voriconazole Use in Children: Therapeutic Drug Monitoring and Control of Inflammation as Key Points for Optimal Treatment

Voriconazole plasma concentrations (PC) are highly variable, particularly in children. Dose recommendations in 2-12-year-old patients changed in 2012. Little data on therapeutic drug monitoring (TDM) after these new recommendations are available. We aimed to evaluate voriconazole monitoring in children with invasive fungal infection (IFI) after implementation of new dosages and its relationship with safety and effectiveness. A prospective, observational study, including children aged 2-12 years, was conducted. TDM was performed weekly and doses were changed according to an in-house protocol. Effectiveness, adverse events, and factors influencing PC were analysed. A total of 229 PC from 28 IFI episodes were obtained. New dosing led to a higher rate of adequate PC compared to previous studies; still, 35.8% were outside the therapeutic range. In patients aged < 8 years, doses to achieve therapeutic levels were higher than recommended. Severe hypoalbuminemia and markedly elevated C-reactive protein were related to inadequate PC. Therapeutic PC were associated with drug effectiveness and safety. Higher doses in younger patients and a dose adjustment protocol based on TDM should be considered. Voriconazole PC variability has decreased with current updated recommendations, but it remains high and is influenced by inflammatory status. Additional efforts to control inflammation in children with IFI should be encouraged.

Comparative study of prophylaxis with high and low doses of voriconazole in children with malignancy

Background and Purpose:

Children with acute myeloid leukemia and relapses of leukemia are at high risk of developing fungal infections and need antifungal prophylaxis. This study aimed to compare the efficacy and toxicity of two different dosage regimens of voriconazole (VRC) during prophylactic administration in children with malignancy and neutropenia.

Materials and Methods:

This prospective study was conducted at the Belarusian Research Center for Pediatric Oncology, Hematology, and Immunology from May 2017 to December 2019. The present study included 21 Caucasian patients with malignant hematological diseases (20 patients with acute myeloid leukemia and relapses of leukemia and 1 patient with Non-Hodgkin's lymphoma) aged 2-18 years. All patients were randomly divided into two groups that received different dosage regimens of VRCZ prophylaxis. Patients in the “high-dose” group received VRCZ at a dose of 9 mg/kg twice a day PO, or 8 mg/kg twice a day IV without a loading dose (children of 2-11 and adolescents and of 12-14 years old with <50 kg weight body), or a dose of 4 mg/kg twice a day PO or IV (adolescents of 12-14 years old with ≥50 kg body weight and all adolescents over 14 years old). Patients in the “low-dose” group received VRCZ at a dose of 4 mg/kg twice a day, PO or IV, without a loading dose (children of 2-11 and adolescents of 12-14 years old with <50 kg body weight), or at a dose of 3 mg/kg twice a day, PO or IV (adolescents of 12-14 years old with ≥ 50 kg body weight and all adolescents over 14 years old). When neutropenia recurred (after the next chemotherapy block), the patients were re-randomized and prophylaxis was resumed in the absence of fungal infection. Therefore, some patients (n=12, 57%) entered the study several times (maximum four times, after each chemotherapy block). In total, 21 patients experienced 40 episodes of VRCZ prophylaxis.

Results:

In the high-dose group (n=20 episodes of prophylaxis), invasive fungal infections (IFI) signs were recorded in one (5%) case. In the low-dose group (n=20 episodes), IFI signs were observed in six (30%) cases (P=0.0375). The residual serum concentration was significantly higher in patients who received high doses of VRCZ (P<0.0001). Most patients with IFI (n=6, 86%) had a mean value (i.e., <0.74 μg/ml) of the residual serum concentration of the medication. Median of the first signs of fungal infection was 22 days from the start of prophylaxis. The dosage was the only highly significant factor that affected the metabolism of VRCZ.

Conclusion:

The likelihood of IFI was significantly lower in children who prophylactically received VRCZ in high doses (P=0.0375) and had ≥ 0.74 μg/ml residual serum concentration of the medication (P=0.0258). Residual serum concentration of VRCZ reached a plateau by day sixth of the treatment. In children, the dosage was the only highly significant factor affecting the metabolism of VRCZ.

Characterization of Therapeutic Drug Monitoring Practices of Voriconazole and Posaconazole at a Pediatric Hospital

OBJECTIVES

To characterize the voriconazole and posaconazole serum trough ordering practices in patients receiving prophylactic and treatment antifungal therapy.

METHODS

A retrospective chart review over a 6-year period of pediatric patients who received voriconazole and/or posaconazole for >24 hours.

RESULTS

A total of 113 patients were included in this study and of these patients, 105 received voriconazole and 16 received posaconazole during the study period. Additionally, 167 trough levels were assessed in this study. Only 50% and 54% of levels were considered within goal recommendations for voriconazole and posaconazole, respectively. The median dose required to achieve goal trough concentration was dependent on drug, indication, and dosage form. Lastly, the most common adverse drug reactions (ADRs) were hepatoxicity, QTc prolongation, and CNS changes, which were in concordance with ADRs documented in the clinical trials for voriconazole and posaconazole. Approximately 20% of patients receiving either voriconazole or posaconazole died during the study period and the median trough in both groups was subtherapeutic.

CONCLUSIONS

Increased monitoring of trough concentrations may be warranted to prevent death or breakthrough invasive fungal infections. Further studies are warranted for assessing the relationship between trough concentrations and treatment outcomes as well as relationship between dosing and achieving goal trough concentrations.

Optimal trough concentration of voriconazole with therapeutic drug monitoring in children: A systematic review and meta-analysis

OBJECTIVES

This systematic review and meta-analysis was designed to determine the optimal trough concentration of voriconazole for children with invasive fungal infections (IFIs).

METHODS

We searched electronic databases (PubMed, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov and Japana Centra Revuo Medicina) for clinical studies describing the voriconazole trough concentration. We used stepwise cut-off values of 1.0-2.0 mg/L for efficacy and 3.0-6.0 mg/L for safety. The efficacy outcomes were treatment success and all-cause mortality, and the safety outcomes were hepatotoxicity, neurotoxicity and all-cause adverse events.

RESULTS

Nine studies involving 211 patients were included in the analysis. The probability of treatment success against IFIs was significantly increased at cut-off values of ≥1.0 mg/L (odds ratio [OR] = 2.65, 95% confidence interval [CI] = 1.20-5.87). Our analysis did not find any relationship between the trough concentration and survival. Concerning safety, the occurrence of any outcomes did not significantly differ according to the voriconazole trough concentrations at any cut-off value. However, in a subgroup analysis of Asian study locations, a significantly higher risk of hepatotoxicity was demonstrated at voriconazole trough cut-off values ≥ 3.0 mg/L (OR = 8.40, 95% CI = 1.36-51.92). Although a significant correlation between the voriconazole concentration and hepatotoxicity was evident in regression curve analysis, (y = 0.1198e^0.2298x), no correlation was demonstrated for neurotoxicity (y = 0.3913e^-0.008x).

CONCLUSION

Our findings suggest that the optimal trough concentration for increasing clinical success and minimizing hepatotoxicity during voriconazole therapy in children with IFIs, particularly for Asian populations, is 1.0-3.0 mg/L.

Effect of Therapeutic Drug Monitoring and Cytochrome P450 2C19 Genotyping on Clinical Outcomes of Voriconazole: A Systematic Review

Objectives

To examine current knowledge on the clinical utility of therapeutic drug monitoring (TDM) in voriconazole therapy, the impact of CYP2C19 genotype on voriconazole plasma concentrations, and the role of CYP2C19 genotyping in voriconazole therapy.

Data Sources

Three literature searches were conducted for original reports on (1) TDM and voriconazole outcomes and (2) voriconazole and CYP2C19 polymorphisms. Searches were conducted through EMBASE, MEDLINE/PubMed, Scopus, and Cochrane Central Register of Controlled Trials from inception to June 2020.

Study Selection and Data Extraction

Randomized controlled trials, cohort studies, and case series with ≥10 patients were included. Only full-text references in English were eligible.

Data Synthesis

A total of 63 studies were reviewed. TDM was recommended because of established concentration and efficacy/toxicity relationships. Voriconazole trough concentrations ≥1.0 mg/L were associated with treatment success; supratherapeutic concentrations were associated with increased neurotoxicity; and hepatotoxicity associations were more prevalent in Asian populations. CYP2C19 polymorphisms significantly affect voriconazole metabolism, but no relationship with efficacy/safety were found. Genotype-guided dosing with TDM was reported to increase chances of achieving therapeutic range.

Relevance to Patient Care and Clinical Practice

Genotype-guided dosing with TDM is a potential solution to optimizing voriconazole efficacy while avoiding treatment failures and common toxicities.

Conclusions

Voriconazole plasma concentrations and TDM are treatment outcome predictors, but research is needed to form a consensus target therapeutic range and dosage adjustment guidelines based on plasma concentrations. CYP2C19 polymorphisms are a predictor of voriconazole concentrations and metabolism, but clinical implications are not established. Large-scale, high-methodological-quality trials are required to investigate the role for prospective genotyping and establish CYP2C19-guided voriconazole dosing recommendations.

Therapeutic Drug Monitoring of Antifungal Drugs: Another Tool to Improve Patient Outcome?

Introduction

This study aimed to examine the relationship among adequate dose, serum concentration and clinical outcome in a non-selected group of hospitalized patients receiving antifungals.

Methods

Prospective cross-sectional study performed between March 2015 and June 2015. Dosage of antifungals was considered adequate according to the IDSA guidelines, whereas trough serum concentrations (determined with HPLC) were considered adequate as follows: fluconazole > 11 µg/ml, echinocandins > 1 µg/ml, voriconazole 1–5.5 µg/ml and posaconazole > 0.7 µg/ml.

Results

During the study period, 84 patients (65.4% male, 59.6 years) received antifungals for prophylaxis (40.4%), targeted (31.0%) and empirical therapy (28.6%). The most frequent drug was micafungin (28/84; 33.3%) followed by fluconazole (23/84; 27.4%), voriconazole (15/84; 17.9%), anidulafungin (8/84; 9.5%), posaconazole (7/84; 8.3%) and caspofungin (3/84; 3.6%). Considerable interindividual variability was observed for all antifungals with a large proportion of the patients (64.3%) not attaining adequate trough serum concentrations, despite receiving an adequate antifungal dose. Attaining the on-target serum antifungal level was significantly associated with a favorable clinical outcome (OR = 0.02; 95% CI 0.01–0.64; p = 0.03), whereas the administration of an adequate antifungal dosage was not.

Conclusions

With the standard antifungal dosage, a considerable proportion of patients have low drug concentrations, which are associated with poor clinical outcome.

Impact of dose adaptations following voriconazole therapeutic drug monitoring in pediatric patients

Voriconazole is the mainstay of treatment for invasive aspergillosis in immunocompromised pediatric patients. Although Therapeutic Drug Monitoring (TDM) of voriconazole is recommended, it remains unknown if TDM-based dose adaptations result in target attainment. Patients <19 years from two pediatric hematologic-oncology wards were retrospectively identified based on unexplained high voriconazole trough concentrations (Cmin > 6 mg/l). Patient demographics, clinical characteristics, treatment, voriconazole dosing information, voriconazole Cmin before and after adjustment based on TDM were obtained. Twenty-one patients, median (range) age 7.0 (1.2-18.5) years, were identified in two centers. First Cmin (3.1 mg/l [0.1-13.5]) was obtained after 3 days (1-27) of treatment. The median of all Cmin (n = 485, median 11 per patient) was 2.16 mg/l (0.0 (undetectable)-28.0), with 24.1% of Cmin < 1 mg/l, 48.9% 1-4 mg/l, 9.3% 4-6 mg/l, and 17.7% > 6 mg/l. Intrapatient variability was large (94.1% for IV, 88.5% for PO). Dose increases at Cmin < 1 mg/l resulted in an increased Cmin in 76.4%, with 60% between 1 and 4 mg/l. Dose decreases at Cmin > 6 mg/l resulted in a decreased Cmin in 80%, with 51% between 1 and 4 mg/l. Overall, in 45% of the cases (33 out of 55 and 12 out of 45) therapeutic targets were attained after dose adjustment. Fifty-five percent of initial Cmin was outside the therapeutic target of 1-4 mg/l, with multiple dose adaptations required to achieve therapeutic concentrations. Only 60% and 51% of dose adaptations following sub- and supra-therapeutic Cmin, respectively, did result in target attainment. Intensive and continuous TDM of voriconazole is a prerequisite for ensuring adequate exposure in pediatric patients.

Therapeutic drug monitoring of systemic antifungal agents: a pragmatic approach for adult and pediatric patients

Introduction: Therapeutic drug monitoring (TDM) has been shown to optimize the management of invasive fungal infections (IFIs), particularly for select antifungal agents with a well-defined exposure-response relationship and an unpredictable pharmacokinetic profile or a narrow therapeutic index. Select triazoles (itraconazole, voriconazole, and posaconazole) and flucytosine fulfill these criteria, while the echinocandins, fluconazole, isavuconazole, and amphotericin B generally do not do so. Given the morbidity and mortality associated with IFIs and the challenges surrounding the use of currently available antifungal agents, TDM plays an important role in therapy.Areas covered: This review seeks to describe the rationale for TDM of antifungal agents, summarize their pharmacokinetic and pharmacodynamic properties, identify treatment goals for efficacy and safety, and provide recommendations for optimal dosing and therapeutic monitoring strategies.Expert opinion: Several new antifungal agents are currently in development, including compounds from existing antifungal classes with enhanced pharmacokinetic or safety profiles as well as agents with novel targets for the treatment of IFIs. Given the predictable pharmacokinetics of these newly developed agents, use of routine TDM is not anticipated. However, expanded knowledge of exposure-response relationships of these compounds may yield a role for TDM to improve outcomes for adult and pediatric patients.

Combination antifungals as an effective means of salvage in paediatric leukaemia patients with invasive fungal infections

Invasive fungal infections (IFIs) are an important cause of morbidity and mortality in paediatric leukaemias. Antifungal combinations to treat these patients are being explored. Fourteen children with leukaemias and IFIs were treated with a combination of antifungal agents at our centre. The first antifungal was amphotericin-B in 13 children and voriconazole in one child. In view of no improvement and clinical deterioration, in nine patients, voriconazole was added as the second antifungal agent and in four, it was caspofungin. All patients completed 4-6 weeks of antifungal therapy. The overall mortality attributable to IFI for the cohort was 4/14 (28%).

UPLC-MS/MS method for the simultaneous determination of imatinib, voriconazole and their metabolites concentrations in rat plasma

In the present study, a simple ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method used to measure the plasma concentrations of imatinib, voriconazole and their metabolites (N-desmethyl imatinib and N-oxide voriconazole) in rats simultaneously making use of diazepam as the internal standard (IS) had been developed and validated. A simple protein precipitation by acetonitrile was employed for the sample preparation, then the analytes (imatinib, voriconazole and their metabolites) were eluted on an Acquity UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) using the mobile phase that made up by acetonitrile (A) and 0.1% formic acid in water (B). In positive ion mode, four analytes and IS were monitored by multiple reaction monitoring (MRM) as the following mass transition pairs: m/z 494.3→394.2 for imatinib, m/z 480.3→394.2 for N-desmethyl imatinib, m/z 350.1→281.1 for voriconazole, m/z 366.1→224.1 for N-oxide voriconazole, and m/z 285.0→154.0 for IS. This method exhibited a good linearity for each analyte. Inter-day and intra-day precision were determined with values of 0.3-14.8% and 2.6-14.8%, respectively; the accuracy values were from -12.5% to 10.2%. Finally, data of matrix effect, extraction recovery, and stability were all conformed to the bioanalytical method validation of acceptance criteria of FDA recommendations. This method is an efficient tool for simultaneous determination of the four analytes and has been successfully applied for pharmacokinetic study in rats.

Therapeutic Drug Monitoring of Voriconazole in Children from a Tertiary Care Center in China

Voriconazole is a broad-spectrum triazole antifungal and the first-line treatment for invasive aspergillosis (IA). The aim of this research was to study the dose adjustments of voriconazole as well as the affecting factors influencing voriconazole trough concentrations in Asian children to optimize its daily administration. Clinical data were analyzed of inpatients 2 to 14 years old who were subjected to voriconazole trough concentration monitoring from 1 June 2015 to 1 December 2017. A total of 138 voriconazole trough concentrations from 42 pediatric patients were included. Voriconazole trough concentrations at steady state ranged from 0.02 to 9.35 mg/liter, with high inter- and intraindividual variability. Only 50.0% of children achieved the target range (1.0 to 5.5 mg/liter) at initial dosing, while 35.7% of children were subtherapeutic, and 14.3% of children were supratherapeutic at initial dosing. There was no correlation between initial trough concentrations and initial dosing. A total of 28.6% of children (12/42) received an adjusted dose according to trough concentrations. Children <6, 6 to 12, and >12 years old required a median oral maintenance dose to achieve the target range of 11.1, 7.2, and 5.3 mg/kg twice daily, respectively (P = 0.043). The average doses required to achieved the target range were 7.7 mg/kg and 5.6 mg/kg, respectively, and were lower than the recommended dosage (P = 0.033 and 0.003, respectively). Affecting factors such as administration routes and coadministration with proton pump inhibitors (PPIs) explained 55.3% of the variability in voriconazole exposure. Therapeutic drug monitoring (TDM) of voriconazole could help to individualize antifungal therapy for children and provide guidelines for TDM and dosing optimization in Asian children.

Pharmacodynamic studies of voriconazole: informing the clinical management of invasive fungal infections

INTRODUCTION

Voriconazole is a broad-spectrum antifungal agent commonly used to treat invasive fungal infections (IFI), including aspergillosis, candidiasis, Scedosporium infection, and Fusarium infection. IFI often occur in immunocompromised patients, leading to increased morbidity and mortality.

AREAS COVERED

The objective of this review is to summarize the pharmacodynamic properties of voriconazole and to provide considerations for potential optimal dosing strategies. Studies have demonstrated superior clinical response when an AUC/MIC >25 or Cmin/MIC >1 is attained in adult patients, correlating to a trough concentration range as narrow as 2-4.5 mg/L; however, these targets are poorly established in the pediatric population. Topics in this discussion include voriconazole use in multiple age groups, predisposing patient factors for IFI, and considerations for clinicians managing IFI. Expert commentary: The relationship between voriconazole dosing and exposure is not well defined due to the large inter- and intra-subject variability. Development of comprehensive decision support tools for individualizing dosing, particularly in children who require higher dosing, will help to increase the probability of achieving therapeutic efficacy and decrease sub-therapeutic dosing and adverse events.

Voriconazole plus caspofungin for treatment of invasive fungal infection in children with acute leukemia

Background

Invasive fungal infections (IFIs) are a life-threatening problem in immunocompromised patients. Despite timely diagnosis and appropriate antifungal therapy, clinical outcomes of IFIs remain unsatisfactory, necessitating treatment with a combination of antifungal agents. Therefore, childhood leukemic patients treated with voriconazole plus caspofungin were evaluated for the safety and efficacy of the combination antifungal therapy to treat IFIs.

Methods

In this retrospective study, medical records were retrieved for patients admitted to the Pediatric Department of Yeungnam University Hospital, Daegu, South Korea, between April 2009 and May 2013. Medical records of 22 patients were analyzed.

Results

Of the 22 patients studied, nine (41%) had been diagnosed with probable IFI, and 13 (59%) with possible IFI. All patients, except one, were already receiving antifungal monotherapy for the treatment of neutropenic fever. After a diagnosis of IFI was confirmed, antifungal monotherapy was replaced with combination therapy. The study's overall response rate was 90.9%, with complete responses in 86.3% of the patients. Two patients experienced a side effect of a small increase in liver enzyme levels.

Conclusion

Voriconazole plus caspofungin combination therapy is an effective and safe treatment for serious IFI in pediatric patients with acute leukemia.

Dose optimisation of voriconazole with therapeutic drug monitoring in children: a single-centre experience in China

The pharmacokinetic profile of voriconazole is highly variable, rendering inconsistent and/or inadequate dosing, especially in children <2 years old. A retrospective analysis was performed in children receiving voriconazole with at least one plasma trough level (C_trough) monitored. Statistical analyses were performed to examine the dose-exposure relationship as well as other factors potentially affecting voriconazole C_trough in children of different ages. A total of 107 paediatric patients were included, of whom 75 were <2 years old. The voriconazole C_trough was highly variable in patients aged <2 years and those aged 2-12 years. Only 47.7% of children reached the therapeutic target of 1.0-5.5 mg/L at initial dosing, whereas 48.6% of C_trough values were subtherapeutic and 3.7% were supratherapeutic. The mean maintenance dose to reach an adequate C_trough was 5.9 mg/kg compared with 5.1 mg/kg, resulting in insufficient levels (P = 0.005) in children aged <2 years. In this age group, the 5 to <7 mg/kg dose range significantly increased the chance of reaching the therapeutic target compared with the 3 to <5 mg/kg dose range (56.7% vs. 25.8%; P = 0.014). Overall, factors such as sex, age, liver function, renal function and co-administered medications explained only 15.9% of variability in voriconazole exposure. Co-administration of omeprazole significantly increased the voriconazole level (P = 0.032), likely through CYP2C19 inhibition. This is the largest series to date describing voriconazole dose-exposure relationships in children aged <2 years. A starting maintenance dose of 5 to <7 mg/kg intravenously twice daily may be required for most children of Asian origin to reach the therapeutic target.

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.

Oral administration and younger age decrease plasma concentrations of voriconazole in pediatric patients

Voriconazole is used for treating or preventing invasive aspergillosis and other invasive fungal infections. To minimize adverse reactions and to maximize treatment effects, therapeutic drug monitoring should be performed. However, it is challenging to optimize daily voriconazole dosing because limited data have been published so far on pediatric patients. We retrospectively analyzed voriconazole concentrations in patients aged 0-18 years. In addition, a literature review was conducted. In our study cohort, younger age and oral administration were significantly associated with lower plasma voriconazole concentrations (P < 0.01). An unfavorable outcome was associated with low concentrations of voriconazole (P = 0.01). Reports of voriconazole administration in pediatric patients show that higher doses are required in younger children and in patients receiving oral administration. Hence, the current data suggest that we should escalate both initial and maintenance doses of voriconazole in pediatric patients, particularly in patients of younger age receiving an oral administration of voriconazole.

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.

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-associated visual disturbances and hallucinations

Voriconazole is a second-generation azole widely used for the prevention and treatment of fungal infection in leukemia patients. Voriconazole is considered the primary antifungal agent for invasive aspergillosis. We report a case of 16-year-old girl who developed visual disturbance and visual and auditory hallucinations after intravenous voriconazole treatment for invasive pulmonary aspergillosis. Due to the visual hallucinations and visual disturbance began acutely and shortly after the initiation of voriconazole, and no other cause could be determined, the symptoms were considered to be the side effects of voriconazole. Simultaneous development of visual side effects and hallucinations rarely have been reported before.

Achieving target voriconazole concentrations more accurately in children and adolescents

Despite the documented benefit of voriconazole therapeutic drug monitoring, nonlinear pharmacokinetics make the timing of steady-state trough sampling and appropriate dose adjustments unpredictable by conventional methods. We developed a nonparametric population model with data from 141 previously richly sampled children and adults. We then used it in our multiple-model Bayesian adaptive control algorithm to predict measured concentrations and doses in a separate cohort of 33 pediatric patients aged 8 months to 17 years who were receiving voriconazole and enrolled in a pharmacokinetic study. Using all available samples to estimate the individual Bayesian posterior parameter values, the median percent prediction bias relative to a measured target trough concentration in the patients was 1.1% (interquartile range, -17.1 to 10%). Compared to the actual dose that resulted in the target concentration, the percent bias of the predicted dose was -0.7% (interquartile range, -7 to 20%). Using only trough concentrations to generate the Bayesian posterior parameter values, the target bias was 6.4% (interquartile range, -1.4 to 14.7%; P = 0.16 versus the full posterior parameter value) and the dose bias was -6.7% (interquartile range, -18.7 to 2.4%; P = 0.15). Use of a sample collected at an optimal time of 4 h after a dose, in addition to the trough concentration, resulted in a nonsignificantly improved target bias of 3.8% (interquartile range, -13.1 to 18%; P = 0.32) and a dose bias of -3.5% (interquartile range, -18 to 14%; P = 0.33). With the nonparametric population model and trough concentrations, our control algorithm can accurately manage voriconazole therapy in children independently of steady-state conditions, and it is generalizable to any drug with a nonparametric pharmacokinetic model. (This study has been registered at ClinicalTrials.gov under registration no. NCT01976078.).

Therapeutic drug monitoring in the treatment of invasive aspergillosis with voriconazole in cancer patients--an evidence-based approach

Invasive aspergillosis (IA) is a life-threatening complication in hematological cancer patients. Voriconazole (VCZ) is the established first-line treatment of IA. VCZ has a nonlinear pharmacokinetic profile and exhibits considerable variability of drug exposure. Therefore, therapeutic drug monitoring (TDM) of VCZ may help to improve treatment results in IA patients, but evidence-based data on the clinical use of TDM in patients treated with VCZ for IA are scarce. Evidence-based guidance is needed to support decisions on the use of TDM in routine VCZ therapy of IA. Our present analysis assessed published studies for evidence-based criteria for TDM of VCZ to improve efficacy and safety of IA therapy in cancer patients. Literature searches of MEDLINE and Cochrane database were performed. We identified 27 clinical studies reporting on the use of plasma level monitoring and/or TDM for VCZ. For each study, strength of recommendation and quality of evidence were categorized according to predefined criteria. A number of studies were published on plasma level monitoring (PLM) and TDM in VCZ therapy of IA. Across studies, VCZ levels >5-5.5 mg/L were found to be associated with toxicity, while reaching minimum levels of >1-2 mg/L appeared to improve efficacy. Timing, frequency, and intervention thresholds and dosage increments of VCZ for adjustment of plasma levels remain to be established. Currently, there is still no conclusive evidence for recommendations in routine clinical practice. More data from prospective randomized studies with TDM are desirable to provide a solid evidence basis for these approaches.

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 pharmacodynamics of antifungals in children and their clinical implications

Invasive fungal infections are a significant cause of morbidity and mortality in children. Successful management of these systemic infections requires identification of the causative pathogen, appropriate antifungal selection, and optimisation of its pharmacokinetic and pharmacodynamic properties to maximise its antifungal activity and minimise toxicity and the emergence of resistance. This review highlights salient scientific advancements in paediatric antifungal pharmacotherapies and focuses on pharmacokinetic and pharmacodynamic studies that underpin current clinical decision making. Four classes of drugs are widely used in the treatment of invasive fungal infections in children, including the polyenes, triazoles, pyrimidine analogues and echinocandins. Several lipidic formulations of the polyene amphotericin B have substantially reduced the toxicity associated with the traditional amphotericin B formulation. Monotherapy with the pyrimidine analogue flucytosine rapidly promotes the emergence of resistance and cannot be recommended. However, when used in combination with other antifungal agents, therapeutic drug monitoring of flucytosine has been shown to reduce high peak flucytosine concentrations, which are strongly associated with toxicity. The triazoles feature large inter-individual pharmacokinetic variability, although this pattern is less pronounced with fluconazole. In clinical trials, posaconazole was associated with fewer adverse effects than other members of the triazole family, though both posaconazole and itraconazole display erratic absorption that is influenced by gastric pH and the gastric emptying rate. Limited data suggest that the clinical response to therapy may be improved with higher plasma posaconazole and itraconazole concentrations. For voriconazole, pharmacokinetic studies among children have revealed that children require twice the recommended adult dose to achieve comparable blood concentrations. Voriconazole clearance is also affected by the cytochrome P450 (CYP) 2C19 genotype and hepatic impairment. Therapeutic drug monitoring is recommended as voriconazole pharmacokinetics are highly variable and small dose increases can result in marked changes in plasma concentrations. For the echinocandins, the primary source of pharmacokinetic variability stems from an age-dependent decrease in clearance with increasing age. Consequently, young children require larger doses per kilogram of body weight than older children and adults. Routine therapeutic drug monitoring for the echinocandins is not recommended. The effectiveness of many systemic antifungal agents has been correlated with pharmacodynamic targets in in vitro and in murine models of invasive candidiasis and aspergillosis. Further study is needed to translate these findings into optimal dosing regimens for children and to understand how these agents interact when multiple antifungal agents are used in combination.

Voriconazole pharmacokinetics and exposure-response relationships: assessing the links between exposure, efficacy and toxicity

The triazole antifungal voriconazole (VCZ) exhibits broad-spectrum antifungal activity and is the first-line treatment for invasive aspergillosis. Highly variable, non-linear pharmacokinetics, metabolism via the polymorphic drug-metabolising enzyme CYP2C19, and a range of serious adverse events (AEs) including hepatotoxicity and neurotoxicity complicate the clinical utility of VCZ. As interest in optimising VCZ treatment has increased, a growing number of studies have examined the relationships between VCZ exposure and efficacy in the treatment and prevention of invasive fungal infections, as well as associations with VCZ-related AEs. This review provides a critical analysis of VCZ pharmacokinetics and exposure-response (E-R) relationships, assessing the links between VCZ exposure, efficacy and toxicity. Low VCZ exposure has frequently been associated with a higher incidence of treatment failure; fewer studies have addressed E-R relationships with prophylactic VCZ. VCZ-related neurotoxicity appears common at high VCZ concentrations and can be minimised by maintaining concentrations below the recommended upper concentration thresholds; hepatotoxicity appears to be associated with increased VCZ exposure but is also prevalent at low concentrations. Further research should aim to inform and optimise the narrow therapeutic range of VCZ as well as develop interventions to individualise VCZ dosing to achieve maximal efficacy with minimal toxicity.

Recent advances in our understanding of the environmental, epidemiological, immunological, and clinical dimensions of coccidioidomycosis

Coccidioidomycosis is the endemic mycosis caused by the fungal pathogens Coccidioides immitis and C. posadasii. This review is a summary of the recent advances that have been made in the understanding of this pathogen, including its mycology, genetics, and niche in the environment. Updates on the epidemiology of the organism emphasize that it is a continuing, significant problem in areas of endemicity. For a variety of reasons, the number of reported coccidioidal infections has increased dramatically over the past decade. While continual improvements in the fields of organ transplantation and management of autoimmune disorders and patients with HIV have led to dilemmas with concurrent infection with coccidioidomycosis, they have also led to advances in the understanding of the human immune response to infection. There have been some advances in therapeutics with the increased use of newer azoles. Lastly, there is an overview of the ongoing search for a preventative vaccine.