Safety, pharmacokinetics, and pharmacodynamics of cyclodextrin itraconazole in pediatric patients with oropharyngeal candidiasis

Pharmacokinetics and pharmacodynamics of cyclodextrin-based oral drug delivery formulations for disease therapy

Oral drug administration has become the most common and preferred mode of disease treatment due to its good medication adherence and convenience. For orally administered drugs, the safety, efficacy, and targeting ability requirements have grown as disease treatment research advances. It is difficult to obtain prominent efficacy of traditional drugs simply via oral administration. Numerous studies have demonstrated that cyclodextrins (CDs) can improve the clinical applications of certain orally administered drugs by enhancing their water solubility and masking undesirable odors. Additionally, deeper studies have discovered that CDs can influence disease treatment by altering the drug pharmacokinetics (PK) or pharmacodynamics (PD). This review highlights recent research progress on the PK and PD effects of CD-based oral drug delivery in disease therapy. Firstly, the review describes the characteristics of current drug delivery modes in oral administration. Besides, we minutely summarized the different CD-containing drugs, focusing on the impact of CD-based alterations in PK or PD of orally administered drugs in treating diseases. Finally, we deeply discussed current challenges and future opportunities with regard to PK and PD of CD-based oral drug delivery formulations.

Development of pediatric orally disintegrating mini-tablets containing atomoxetine hydrochloride-β-cyclodextrin inclusion complex using experimental design

OBJECTIVE

The aim of the study was to develop and evaluate characteristics of orally disintegrating mini-tablet (ODMT) formulations including atomoxetine hydrochloride (ATO)/β-cyclodextrin (β-CD) inclusion complex for pediatric therapy of attention deficit and hyperactivity disorder (ADHD).

METHODS

Design of experiment approach was used to develop ODMTs. The ODMTs were compressed using direct compression method with two different superdisintegrants (Parteck ODT^® and Ac-Di-Sol^®) and characterized with quality control tests. In vitro dissolution and taste studies were performed.

RESULTS

The hardness and friability values of the optimized three ODMT formulations were determined as 41.7 N, 42.4 N, and 40.8 N and 0.32%, 0.29%, and 0.42%, respectively. The disintegration time of all the optimized formulations was found to be less than one minute. In addition, dissolution profiles of ATO from optimized ODMTs were determined in four different dissolution media (distilled water, pH 1.2, 6.8, and 7.4) and it was determined that the maximum dissolved ATO amount reached at the end of 20 min.

CONCLUSION

As a conclusion, the novel formulation of ODMTs with ATO/β-CD inclusion complex was successfully developed for pediatric use.

The Current States, Challenges, Ongoing Efforts, and Future Perspectives of Pharmaceutical Excipients in Pediatric Patients in Each Country and Region

A major hurdle in pediatric formulation development is the lack of safety and toxicity data on some of the commonly used excipients. While the maximum oral safe dose for several kinds of excipients is known in the adult population, the doses in pediatric patients, including preterm neonates, are not established yet due to the lack of evidence-based data. This paper consists of four parts: (1) country-specific perspectives in different parts of the world (current state, challenges in excipients, and ongoing efforts) for ensuring the use of safe excipients, (2) comparing and contrasting the country-specific perspectives, (3) past and ongoing collaborative efforts, and (4) future perspectives on excipients for pediatric formulation. The regulatory process for pharmaceutical excipients has been developed. However, there are gaps between each region where a lack of information and an insufficient regulation process was found. Ongoing efforts include raising issues on excipient exposure, building a region-specific database, and improving excipient regulation; however, there is a lack of evidence-based information on safety for the pediatric population. More progress on clear safety limits, quantitative information on excipients of concern in the pediatric population, and international harmonization of excipients’ regulatory processes for the pediatric population are required.

Safety, Tolerability, and Population Pharmacokinetics of Intravenous and Oral Isavuconazonium Sulfate in Pediatric Patients

Isavuconazole, administered as the water-soluble prodrug isavuconazonium sulfate, is a new triazole agent used to treat invasive fungal infections. This phase 1 study evaluated the pharmacokinetics (PK), safety, and tolerability of isavuconazole in 46 immunocompromised pediatric patients, stratified by age (1 to <6 [intravenous (i.v.) only], 6 to <12, and 12 to <18 years), receiving 10 mg/kg body weight (maximum, 372 mg) isavuconazonium sulfate either i.v. or orally. A population PK model using weight-based allometric scaling was constructed with the pediatric i.v. and oral data plus i.v. data from a phase 1 study in adults. The best model was a 3-compartment model with combined zero-order and first-order input, with linear elimination. Stepwise covariate modeling was performed in Perl-speaks-NONMEM version 4.7.0. None of the covariates examined, including age, sex, race, and body mass index, were statistically significant for any of the PK parameters. The area under the concentration-time curve at steady state (AUC_SS) was predicted for pediatric patients using 1,000 Monte Carlo simulations per age cohort for each administration route. The probability of target attainment (AUC_SS range, 60 to 233 μg · h/ml) was estimated; this target range was derived from plasma drug exposures in adults receiving the recommended clinical dose. Predicted plasma drug exposures were within the target range for >80% and >76% of simulated pediatric patients following i.v. or oral administration, respectively. Intravenous and oral administration of isavuconazonium sulfate at the studied dosage of 10 mg/kg was well tolerated and resulted in exposure in pediatric patients similar to that in adults. (This study has been registered at ClinicalTrials.gov under identifier NCT03241550).

Methodological features of clinical pharmacokinetic-pharmacodynamic studies of antibacterials and antifungals: a systematic review

BACKGROUND

Pharmacokinetic (PK)-pharmacodynamic (PD) indices relate measures of drug exposure to antibacterial effect. Clinical PK-PD studies aim to correlate PK-PD indices with outcomes in patients. Optimization of dosing based on pre-clinical studies means that PK-PD relationships are difficult to establish; therefore studies need to be designed and reported carefully to validate pre-clinical findings.

OBJECTIVES

To describe the methodological features of clinical antibacterial and antifungal PK-PD studies that reported the relationship between PK-PD indices and clinical or microbiological responses.

METHODS

Studies published between 1980 and 2015 were identified through systematic searches. Methodological features of eligible studies were extracted.

RESULTS

We identified 85 publications containing 97 PK-PD analyses. Most studies were small, with fewer than 100 patients. Around a quarter were performed on patients with infections due to a single specific pathogen. In approximately one-third of studies, patients received concurrent antibiotics/antifungals and in some other studies patients received other treatments that may confound the PK-PD-outcome relationship. Most studies measured antimicrobial concentrations in blood/serum and only four measured free concentrations. Most performed some form of regression, time-to-event analysis or used the Hill/Emax equation to examine the association between PK-PD index and outcome. Target values of PK-PD indices that predict outcomes were investigated in 52% of studies. Target identification was most commonly done using recursive partitioning or logistic regression.

CONCLUSIONS

Given the variability in conduct and reporting, we suggest that an agreed set of standards for the conduct and reporting of studies should be developed.

Clinical Pharmacokinetics of Triazoles in Pediatric Patients

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

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.

ESCMID-ECMM guideline: diagnosis and management of invasive aspergillosis in neonates and children

SCOPE

Presenting symptoms, distributions and patterns of diseases and vulnerability to invasive aspergillosis (IA) are similar between children and adults. However, differences exist in the epidemiology and underlying conditions, the usefulness of newer diagnostic tools, the pharmacology of antifungal agents and in the evidence from interventional phase 3 clinical trials. Therefore, the European Society for Clinical Microbiology and Infectious Diseases (ESCMID) and the European Confederation of Medical Mycology (ECMM) have developed a paediatric-specific guideline for the diagnosis and management of IA in neonates and children.

METHODS

Review and discussion of the scientific literature and grading of the available quality of evidence was performed by the paediatric subgroup of the ESCMID-ECMM-European Respiratory Society (ERS) Aspergillus disease guideline working group, which was assigned the mandate for the development of neonatal- and paediatric-specific recommendations.

QUESTIONS

Questions addressed by the guideline included the epidemiology of IA in neonates and children; which paediatric patients may benefit from antifungal prophylaxis; how to diagnose IA in neonates and children; which antifungal agents are available for use in neonates and children; which antifungal agents are suitable for prophylaxis and treatment of IA in neonates and children; what is the role of therapeutic drug monitoring of azole antifungals; and which management strategies are suitable to be used in paediatric patients. This guideline provides recommendations for the diagnosis, prevention and treatment of IA in the paediatric population, including neonates. The aim of this guideline is to facilitate optimal management of neonates and children at risk for or diagnosed with IA.

Itraconazole Dosing and Drug Monitoring at a Tertiary Children's Hospital

BACKGROUND

Itraconazole is a broad-spectrum antifungal agent used for prophylaxis and treatment of fungal infections in immunocompromised children. Achieving the recommended target serum itraconazole trough concentration of ≥0.5 mg/L is challenging in children because of variation in itraconazole pharmacokinetics with age. We studied itraconazole use and treatment outcomes in a tertiary children's hospital.

METHODS

We did a 10-year retrospective review of medical records of children at the Royal Children's Hospital Melbourne who received oral itraconazole and had therapeutic drug monitoring (TDM).

RESULTS

Overall, 81 children received 92 courses of oral itraconazole and had TDM. Of 222 TDM samples, 183 (82.4%) were taken at the appropriate time (trough level at steady state). Patients ≤12 and >12 years of age required median doses of 6.2 and 3.9 mg/kg/d, respectively, to attain target trough levels (P < 0.001). Of children ≤12 years of age, 71.4% required doses above the recommended dose of 5 mg/kg/d to achieve therapeutic levels, compared with 17.4% of those >12 years of age. At least 1 subtherapeutic trough concentration was reported in 63 (76.8%) courses; in only 18 (28.6%) of these was the dose adjusted. Gastrointestinal symptoms [14/92 (15.2%) courses] and hepatotoxicity [6/92 (6.5%)] were the most frequent adverse events. Neither was associated with elevated trough levels.

CONCLUSIONS

The poor attainment of target levels with current recommended dosing in children <12 years of age suggests that higher empiric doses are needed in this age group. The poor compliance with TDM guidelines highlights the need for better education about appropriate timing of sampling and dose adjustment.

Invasive Aspergillosis in Children: Update on Current Guidelines

Invasive aspergillosis (IA) is an important cause of infectious morbidity and mortality in immunocompromised paediatric patients. Despite improvements in diagnosis, prevention, and treatment, IA is still associated with high mortality rates. To address this issue, several international societies and organisations have proposed guidelines for the management of IA in the paediatric population. In this article, we review current recommendations of the Infectious Diseases Society of America, the European Conference on Infection in Leukaemia and the European Society of Clinical Microbiology and Infectious Diseases for the management and prevention of IA in children.

Diagnosis and management of Aspergillus diseases: executive summary of the 2017 ESCMID-ECMM-ERS guideline

The European Society for Clinical Microbiology and Infectious Diseases, the European Confederation of Medical Mycology and the European Respiratory Society Joint Clinical Guidelines focus on diagnosis and management of aspergillosis. Of the numerous recommendations, a few are summarized here. Chest computed tomography as well as bronchoscopy with bronchoalveolar lavage (BAL) in patients with suspicion of pulmonary invasive aspergillosis (IA) are strongly recommended. For diagnosis, direct microscopy, preferably using optical brighteners, histopathology and culture are strongly recommended. Serum and BAL galactomannan measures are recommended as markers for the diagnosis of IA. PCR should be considered in conjunction with other diagnostic tests. Pathogen identification to species complex level is strongly recommended for all clinically relevant Aspergillus isolates; antifungal susceptibility testing should be performed in patients with invasive disease in regions with resistance found in contemporary surveillance programmes. Isavuconazole and voriconazole are the preferred agents for first-line treatment of pulmonary IA, whereas liposomal amphotericin B is moderately supported. Combinations of antifungals as primary treatment options are not recommended. Therapeutic drug monitoring is strongly recommended for patients receiving posaconazole suspension or any form of voriconazole for IA treatment, and in refractory disease, where a personalized approach considering reversal of predisposing factors, switching drug class and surgical intervention is also strongly recommended. Primary prophylaxis with posaconazole is strongly recommended in patients with acute myelogenous leukaemia or myelodysplastic syndrome receiving induction chemotherapy. Secondary prophylaxis is strongly recommended in high-risk patients. We strongly recommend treatment duration based on clinical improvement, degree of immunosuppression and response on imaging.

Antifungal azoles itraconazole and posaconazole exhibit potent in vitro antiviral activity against clinical isolates of parechovirus A3 (Picornaviridae)

Parechovirus A3 (Par-A3, formerly human parechovirus 3) is an emerging viral infection of the central nervous system in children. We used an automated, homogeneous, cell based assay to identify itraconazole and posaconazole as inhibitors of Par-A3, with antiviral activity below concentrations clinically attainable in pediatric patients. Currently, there is no approved antiviral treatment for Par-A3 infection, despite numerous reports of serious Par-A3 disease in neonates and infants.

Antifungal Drugs in Newborns and Children

Invasive fungal infections are a significant cause of morbidity and mortality in infants and children. Early diagnosis is critical, and treatment with the appropriate drug and dose should be initiated promptly. Although an increasing number of studies have examined dosing of antifungals in this population, pediatric safety and efficacy data are lacking.

Effects of Membrane PEGylation on Entry and Location of Antifungal Drug Itraconazole and Their Pharmacological Implications

Itraconazole (ITZ) is an antifungal agent used clinically to treat mycotic infections. However, its therapeutic effects are limited by low solubility in aqueous media. Liposome-based delivery systems (LDS) have been proposed as a delivery mechanism for ITZ to alleviate this problem. Furthermore, PEGylation, the inclusion in the formulation of a protective "stealth sheath" of poly(ethylene glycol) around carrier particles, is widely used to increase circulation time in the bloodstream and hence efficacy. Together, these themes highlight the importance of mechanistic and structural understanding of ITZ incorporation into liposomes both with and without PEGylation because it can provide a potential foundation for the rational design of LDS-based systems for delivery of ITZ, using alternate protective polymers or formulations. Here we have combined atomistic simulations, cryo-TEM, Langmuir film balance, and fluorescence quenching experiments to explore how ITZ interacts with both pristine and PEGylated liposomes. We found that the drug can be incorporated into conventional and PEGylated liposomes for drug concentrations up to 15 mol % without phase separation. We observed that, in addition to its protective properties, PEGylation significantly increases the stability of liposomes that host ITZ. In a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer without PEGylation, ITZ was found to reside inside the lipid bilayer between the glycerol and the double-bond regions of POPC, adopting a largely parallel orientation along the membrane surface. In a PEGylated liposome, ITZ partitions mainly to the PEG layer. The results provide a solid basis for further development of liposome-based delivery systems.

Successful empirical antifungal therapy of intravenous itraconazole with pharmacokinetic evidence in pediatric cancer patients undergoing hematopoietic stem cell transplantation

BACKGROUND AND OBJECTIVES

Empirical antifungal therapy prevents invasive fungal infections in patients with cancer. This study assessed the empirical efficacy of intravenous itraconazole in pediatric patients undergoing hematopoietic stem cell transplantation, and investigated the pharmacokinetics and clinical implications.

METHODS

Oral itraconazole syrup was started (2.5 mg/kg twice daily) for prophylaxis, and patients with persistent neutropenic fever for more than 2 days were switched to intravenous itraconazole (5 mg/kg twice daily for 2 days for induction and 5 mg/kg daily for maintenance) as empirical treatment. Empirical antifungal efficacy was assessed retrospectively in 159 transplantations, and a full pharmacokinetic study was prospectively conducted in six of these patients. Successful antifungal efficacy was defined as the fulfillment of all components of a five-part composite end point.

RESULTS

The overall empirical antifungal success rate fulfilling all criteria was 42.1 %. No death or drug-related serious adverse events occurred during the study. Mean trough plasma concentration of itraconazole after oral prophylaxis and intravenous induction were 577.2 and 1659.7 μg/L, respectively. Mean area under the concentration-time curve of itraconazole and its metabolite at steady state were 42,837 ± 24,746 μg·h/L and 63,094 ± 19,255 μg·h/L.

CONCLUSIONS

Intravenous itraconazole was effective and safe as an empirical antifungal agent in pediatric patients; this was due to the fast and satisfactory increase in drug concentration by switching from oral to intravenous therapy.

Consensus guidelines for the treatment of yeast infections in the haematology, oncology and intensive care setting, 2014

Pathogenic yeast forms are commonly associated with invasive fungal disease in the immunocompromised host, including patients with haematological malignancies and patients of haemopoietic stem cell transplants. Yeasts include the Candida spp., Cryptococcus spp., Pneumocystis jirovecii and some lesser-known pathogens. Candida species remain the most common cause of invasive yeast infections (and the most common human pathogenic fungi). These guidelines present evidence-based recommendations for the antifungal management of established, invasive yeast infections in adult and paediatric patients in the haematology/oncology setting. Consideration is also given to the critically ill patient in intensive care units, including the neonatal intensive care unit. Evidence for 'pre-emptive' or 'diagnostic-driven antifungal therapy' is also discussed. For the purposes of this paper, invasive yeast diseases are categorised under the headings of invasive candidiasis, cryptococcosis and uncommon yeast infections. Specific recommendations for the management of Pneumocystis jirovecii are presented in an accompanying article (see consensus guidelines by Cooley et al. appearing elsewhere in this supplement).

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.

Advances in the treatment of invasive neonatal candidiasis

INTRODUCTION

Invasive candidiasis is responsible for ∼ 10% of nosocomial sepsis in very-low-birth-weight infants and is associated with substantial morbidity and mortality. Over the last two decades, the antifungal armamentarium against Candida spp. has increased; however, efficacy and safety studies in this population are lacking.

AREAS COVERED

We reviewed the medical literature and extracted information on clinical and observational studies evaluating the use of antifungal agents in neonates with invasive candidiasis.

EXPERT OPINION

Efficacy and safety data for antifungals in neonates are lacking, and the majority of studies conducted to date have concentrated on pharmacokinetic/pharmacodynamic evaluations. Unlike other anti-infective agents, efficacy data in the setting of neonatal candidiasis cannot be extrapolated from adult studies due to differences in the pathophysiology of the disease in this population relative to older children and adults. Data for amphotericin B deoxycholate, fluconazole, and micafungin suggest that these are the current agents of choice for this disease in neonates until data for newer antifungal agents become available. For prophylaxis, data from fluconazole randomized controlled trials will be submitted to the regulatory agencies for labeling. Ultimately, the field of therapeutics for neonatal candidiasis will require multidisciplinary collaboration given the numerous challenges associated with conducting clinical trials in neonates.

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.

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.

Pharmacokinetic/pharmacodynamic modelling approaches in paediatric infectious diseases and immunology

Pharmacokinetic/pharmacodynamic (PKPD) modelling is used to describe and quantify dose-concentration-effect relationships. Within paediatric studies in infectious diseases and immunology these methods are often applied to developing guidance on appropriate dosing. In this paper, an introduction to the field of PKPD modelling is given, followed by a review of the PKPD studies that have been undertaken in paediatric infectious diseases and immunology. The main focus is on identifying the methodological approaches used to define the PKPD relationship in these studies. The major findings were that most studies of infectious diseases have developed a PK model and then used simulations to define a dose recommendation based on a pre-defined PD target, which may have been defined in adults or in vitro. For immunological studies much of the modelling has focused on either PK or PD, and since multiple drugs are usually used, delineating the relative contributions of each is challenging. The use of dynamical modelling of in vitro antibacterial studies, and paediatric HIV mechanistic PD models linked with the PK of all drugs, are emerging methods that should enhance PKPD-based recommendations in the future.

Antifungal agents and therapy for infants and children with invasive fungal infections: a pharmacological perspective

Invasive fungal infections, although relatively rare, are life-threatening diseases in premature infants and immunocompromised children. While many advances have been made in antifungal therapeutics in the last two decades, knowledge of the pharmacokinetics and pharmacodynamics of antifungal agents for infants and children remains incomplete. This review summarizes the pharmacology and clinical utility of currently available antifungal agents and discusses the opportunities and challenges for future research.

Itraconazole: an update on pharmacology and clinical use for treatment of invasive and allergic fungal infections

INTRODUCTION

Fungal infections are a major source of global morbidity and mortality. Itraconazole is a triazole antifungal agent that is widely used for the prevention and treatment of fungal infection. While newer antifungal agents are now available, itraconazole is an orally bioavailable agent with broad-spectrum antifungal activity. Itraconazole remains a useful drug for the management of allergic and invasive mycoses worldwide.

AREAS COVERED

This article provides a summary of the pharmacokinetics, pharmacodynamics and clinical uses of itraconazole. Additionally, the authors summarise the safety and recently described toxicodynamics and discuss the value of therapeutic drug monitoring (TDM) with itraconazole. The following search criteria were constructed in order to identify relevant literature using PubMed and Ovid-MEDLINE: itraconazole, triazole, pharmacokinetics, pharmacodynamics, toxicodynamics and TDM. Relevant abstracts and articles identified from reviewing secondary citations were additionally retrieved and included if relevant.

EXPERT OPINION

Itraconazole remains an important agent in the prevention and treatment of fungal infection. Itraconazole has a broad-spectrum of activity and is available in both an intravenous and oral form making long-term use in chronic mycoses practical. Itraconazole is widely used for the treatment of endemic fungal infections. Pharmacokinetic variability and clinically important drug interactions make TDM of itraconazole an important consideration.

Antifungal agents for the treatment of systemic fungal infections in children

Traditionally, the mainstay of systemic antifungal therapy has been amphotericin B deoxycholate (conventional amphotericin B). Newer agents have been developed to fulfill special niches and to compete with conventional amphotericin B by virtue of having more favourable toxicity profiles. Some agents have displaced conventional amphotericin B for the treatment of specific fungal diseases. For example, voriconazole has emerged as the preferred treatment for invasive pulmonary aspergillosis. This notwithstanding, conventional amphotericin B remains a useful agent for the treatment of paediatric fungal infections. Knowledge of the characteristics of the newer agents is important, given the increasing numbers of patients who are being treated with these drugs. Efforts need to be directed at research aimed at generating paediatric data where these are lacking. The antifungal agents herein described are most often used as monotherapy regimens because there is no uniform consensus on the value of combination therapy, except for specific scenarios.

Long-term parenteral administration of 2-hydroxypropyl-β-cyclodextrin causes bone loss

Cyclodextrins are oligosaccharides which are used in the pharmaceutical industry and research as vehicles for application of apolar substances such as steroids. The aim of this study was to examine the long-term effects of parenteral administration of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) on bone. Sham-operated (SHAM) or ovariectomized (OVX) adult rats were subcutaneously injected with physiological saline, 50, or 200 mg/kg HP-β-CD daily. After 4 months, body weight in OVX rats and uterine weight in SHAM rats were significantly lower after administration of 200 mg/kg HP-β-CD, relative to vehicle controls. At 200 mg/kg, HP-β-CD was hepatotoxic as measured by increased serum transaminases, and reduced serum albumin. Moreover, 200 mg/kg HP-β-CD led to decreased vertebral and tibial bone mineral density (BMD), and to cortical thinning at the tibial shaft. Bone loss in HP-β-CD-treated rats was associated with increased bone resorption as measured by increased renal deoxypyridinoline excretion. Although 50 mg/kg HP-β-CD was devoid of overt signs of organ toxicity and did not impair BMD, bone resorption was already increased. In summary, subcutaneous long-term administration of HP-β-CD at a daily dose of 200 mg/kg led to increased bone resorption and subsequent bone loss. Minor alterations in bone metabolism were also seen at 50 mg/kg.

Resurgence in the use of physiologically based pharmacokinetic models in pediatric clinical pharmacology: parallel shift in incorporating the knowledge of biological elements and increased applicability to drug development and clinical practice

AIMS AND OBJECTIVES

(i) To describe an example of the development work required for building a 'pediatric physiologically based pharmacokinetic' (P-PBPK) model (Simcyp Pediatric ADME Simulator), (ii) to replicate pediatric clinical studies and undertake theoretical studies to show the potential applications of mechanistic PBPK in pediatric drug clinical investigation and practice, with emphasis on pediatric anesthesia.

BACKGROUND

PBPK models draw together the physiological and biochemical information that determine drug absorption, distribution, metabolism, and excretion and then link them in a physiologically realistic 'systems' model. Incorporating the emerging additional information on developmental physiology and biochemistry has resulted in the creation of P-PBPK. There has been a renewed interest in the application of such modeling by the pharmaceutical industry to improve the efficiency of drug development, especially in populations where designing and conducting clinical studies is more challenging, such as pediatric patients.

METHODS

P-PBPK was used to simulate a number of published clinical studies and clinical case scenarios with the aim of highlighting the potential applications.

RESULTS

Changing the P-PBPK model parameters in a number of 'what if' simulations were used to explore the likely underlying reasons for observed pharmacokinetic (PK) behavior of drugs in critically ill children. In addition, the use of P-PBPK models to predict complex drug-drug interactions (DDI) highlighted disparities with adult populations.

DISCUSSION

The examples highlight the use of prior knowledge of in vitro drug attributes and biology of the system (human body) to simulate PK and multiple DDI scenarios not infrequently encountered in critically ill pediatric patients.

Pharmacokinetics and biodistribution of itraconazole in rats and mice following intravenous administration in a novel liposome formulation

Novel itraconazole (ITZ)-loaded liposomes (ITZ-LPs) were prepared and their pharmacokinetics and biodistribution were assessed in comparison with commercial formulations (ITZ-CD). The ITZ-LPs were prepared by thin-film hydration method and the physicochemical characterizations of the ITZ-LPs were evaluated. The pharmacokinetics and biodistribution were studied in the rats and mice, and compared with commercially available formulations (Sporanox((R))) after administration by the tail vein at a dose of 10 mg/kg. The concentration of ITZ in plasma and tissues was determined by means of HPLC-MS/MS. The size distribution of the liposomes was 264.5 nm and the entrapment efficiency of ITZ-LPs was 73.82 +/- 0.73%. In pharmacokinetics study, the two formulations demonstrated pronounced differences following i.v. administration to rats. The AUC(0-->24 h) for ITZ-CD was 87.12 mg/L.h and that for ITZ-LPs was 155.47 mg/L.h (p < 0.05). The MRT(0-->24 h) value was 1.70 h for ITZ-CD and 3.68 h for ITZ-LPs. In tissue distribution study, there were no differences of distributions in the lung between two formulations. Nevertheless, in the liver and spleen, itraconazole levels for the group treated with ITZ-LPs were significantly higher than those for the group treated with ITZ-CD. Meanwhile, the low distribution of ITZ-LPs in heart and kidney was of great advantage to reduce the toxicity for heart and kidney. These results indicated that the ITZ-LPs can be a potential intravenous formulation of itraconazole.

Antifungal agents for the treatment of systemic fungal infections in children

Traditionally, the mainstay of systemic antifungal therapy has been amphotericin B deoxycholate (conventional amphotericin B). Newer agents have been developed to fulfill special niches and to compete with conventional amphotericin B by virtue of having more favourable toxicity profiles. Some agents have displaced conventional amphotericin B for the treatment of specific fungal diseases. For example, voriconazole has emerged as the preferred treatment for invasive pulmonary aspergillosis. This notwithstanding, conventional amphotericin B remains a useful agent for the treatment of paediatric fungal infections. Knowledge of the characteristics of the newer agents is important, given the increasing numbers of patients who are being treated with these drugs. Efforts need to be directed at research aimed at generating paediatric data where these are lacking. The antifungal agents herein described are most often used as monotherapy regimens because there is no uniform consensus on the value of combination therapy, except for specific scenarios.

Cyclodextrin-complexed curcumin exhibits anti-inflammatory and antiproliferative activities superior to those of curcumin through higher cellular uptake

Curcumin, a yellow pigment present in the spice turmeric (Curcuma longa), has been linked with multiple beneficial activities, but its optimum potential is limited by poor bioavailability, in part due to the lack of solubility in aqueous solvents. To overcome the solubility problem, we have recently developed a novel cyclodextrin complex of curcumin (CDC) and examined here this compound for anti-inflammatory and antiproliferative effects. Using the electrophoretic mobility shift assay, we found that CDC was more active than free curcumin in inhibiting TNF-induced activation of the inflammatory transcription factor NF-kappaB and in suppressing gene products regulated by NF-kappaB, including those involved in cell proliferation (cyclin D1), invasion (MMP-9), and angiogenesis (VEGF). CDC was also more active than free curcumin in inducing the death receptors DR4 and DR5. Annexin V staining, cleavage of caspase-3 and PARP, and DNA fragmentation showed that CDC was more potent than free curcumin in inducing apoptosis of leukemic cells. Antiproliferative assays also demonstrated that CDC was more active than free curcumin in suppressing proliferation of various cancer cell lines. The cyclodextrin vehicle had no effect in these assays. Compared with free curcumin, CDC had a greater cellular uptake and longer half-life in the cells. Overall we demonstrated that CDC had superior attributes compared with free curcumin for cellular uptake and for antiproliferative and anti-inflammatory activities.

Pediatric antifungal agents

PURPOSE OF REVIEW

In immunocompromised hosts, invasive fungal infections are common and fatal. In the past decade, the antifungal armamentarium against invasive mycoses has expanded greatly. The purpose of the present report is to review the most recent literature addressing the use of antifungal agents in children.

RECENT FINDINGS

Most studies evaluating the safety and efficacy of antifungal agents are limited to adults. However, important progress has been made in describing the pharmacokinetics and safety of newer antifungal agents in children, including the echinocandins.

SUMMARY

Dosage guidelines for newer antifungal agents are currently based on adult and limited pediatric data. Because important developmental pharmacology changes occur throughout childhood impacting the pharmacokinetics of these agents, antifungal studies specifically designed for children are necessary.

Guidelines for the Prevention and Treatment of Opportunistic Infections among HIV-exposed and HIV-infected children: recommendations from CDC, the National Institutes of Health, the HIV Medicine Association of the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, and the American Academy of Pediatrics

This report updates and combines into one document earlier versions of guidelines for preventing and treating opportunistic infections (OIs) among HIV-exposed and HIV-infected children, last published in 2002 and 2004, respectively. These guidelines are intended for use by clinicians and other health-care workers providing medical care for HIV-exposed and HIV-infected children in the United States. The guidelines discuss opportunistic pathogens that occur in the United States and one that might be acquired during international travel (i.e., malaria). Topic areas covered for each OI include a brief description of the epidemiology, clinical presentation, and diagnosis of the OI in children; prevention of exposure; prevention of disease by chemoprophylaxis and/or vaccination; discontinuation of primary prophylaxis after immune reconstitution; treatment of disease; monitoring for adverse effects during treatment; management of treatment failure; prevention of disease recurrence; and discontinuation of secondary prophylaxis after immune reconstitution. A separate document about preventing and treating of OIs among HIV-infected adults and postpubertal adolescents (Guidelines for the Prevention and Treatment of Opportunistic Infections in HIV-Infected Adults and Adolescents) was prepared by a working group of adult HIV and infectious disease specialists. The guidelines were developed by a panel of specialists in pediatric HIV infection and infectious diseases (the Pediatric Opportunistic Infections Working Group) from the U.S. government and academic institutions. For each OI, a pediatric specialist with content-matter expertise reviewed the literature for new information since the last guidelines were published; they then proposed revised recommendations at a meeting at the National Institutes of Health (NIH) in June 2007. After these presentations and discussions, the guidelines underwent further revision, with review and approval by the Working Group, and final endorsement by NIH, CDC, the HIV Medicine Association (HIVMA) of the Infectious Diseases Society of America (IDSA), the Pediatric Infectious Disease Society (PIDS), and the American Academy of Pediatrics (AAP). The recommendations are rated by a letter that indicates the strength of the recommendation and a Roman numeral that indicates the quality of the evidence supporting the recommendation so readers can ascertain how best to apply the recommendations in their practice environments. An important mode of acquisition of OIs, as well as HIV infection among children, is from their infected mother; HIV-infected women coinfected with opportunistic pathogens might be more likely than women without HIV infection to transmit these infections to their infants. In addition, HIV-infected women or HIV-infected family members coinfected with certain opportunistic pathogens might be more likely to transmit these infections horizontally to their children, resulting in increased likelihood of primary acquisition of such infections in the young child. Therefore, infections with opportunistic pathogens might affect not just HIV-infected infants but also HIV-exposed but uninfected infants who become infected by the pathogen because of transmission from HIV-infected mothers or family members with coinfections. These guidelines for treating OIs in children therefore consider treatment of infections among all children, both HIV-infected and uninfected, born to HIV-infected women. Additionally, HIV infection is increasingly seen among adolescents with perinatal infection now surviving into their teens and among youth with behaviorally acquired HIV infection. Although guidelines for postpubertal adolescents can be found in the adult OI guidelines, drug pharmacokinetics and response to treatment may differ for younger prepubertal or pubertal adolescents. Therefore, these guidelines also apply to treatment of HIV-infected youth who have not yet completed pubertal development. Major changes in the guidelines include 1) greater emphasis on the importance of antiretroviral therapy for preventing and treating OIs, especially those OIs for which no specific therapy exists; 2) information about the diagnosis and management of immune reconstitution inflammatory syndromes; 3) information about managing antiretroviral therapy in children with OIs, including potential drug--drug interactions; 4) new guidance on diagnosing of HIV infection and presumptively excluding HIV infection in infants that affect the need for initiation of prophylaxis to prevent Pneumocystis jirovecii pneumonia (PCP) in neonates; 5) updated immunization recommendations for HIV-exposed and HIV-infected children, including hepatitis A, human papillomavirus, meningococcal, and rotavirus vaccines; 6) addition of sections on aspergillosis; bartonella; human herpes virus-6, -7, and -8; malaria; and progressive multifocal leukodystrophy (PML); and 7) new recommendations on discontinuation of OI prophylaxis after immune reconstitution in children. The report includes six tables pertinent to preventing and treating OIs in children and two figures describing immunization recommendations for children aged 0--6 years and 7--18 years. Because treatment of OIs is an evolving science, and availability of new agents or clinical data on existing agents might change therapeutic options and preferences, these recommendations will be periodically updated and will be available at http://AIDSInfo.nih.gov.