Pharmacokinetics of antifungal agents in children

Clinical treatment of cryptococcal meningitis: an evidence-based review on the emerging clinical data

Cryptococcal meningitis (CM) is a fatal fungal central nervous system (CNS) infection caused by Cryptococcus infecting the meninges and/or brain parenchyma, with fever, headache, neck stiffness, and visual disturbances as the primary clinical manifestations. Immunocompromised individuals with human immunodeficiency virus (HIV) infection or who have undergone organ transplantation, as well as immunocompetent people can both be susceptible to CM. Without treatment, patients with CM may have a mortality rate of up to 100% after hospital admission. Even after receiving therapy, CM patients may still suffer from problems such as difficulty to cure, poor prognosis, and high mortality. Therefore, timely and effective treatment is essential to improve the mortality and prognosis of CM patients. Currently, the clinical outcomes of CM are frequently unsatisfactory due to limited drug choices, severe adverse reactions, drug resistance, etc. Here, we review the research progress of CM treatment strategies and discuss the suitable options for managing CM, hoping to provide a reference for physicians to select the most appropriate treatment regimens for CM patients.

Cutaneous Leishmania mexicana infections in the United States: defining strains through endemic human pediatric cases in northern Texas

Over a 6-month span, three patients under 5 years old with cutaneous leishmaniasis presented to the Pediatric Infectious Diseases Clinic at the University of Texas Southwestern Medical Center/Children's Health Dallas. None had traveled outside of northern Texas/southern Oklahoma; all had Leishmania mexicana infections confirmed by PCR. We provide case descriptions and images to increase the awareness of this disease among United States (US) physicians and scientists. Two patients responded to fluconazole, but the youngest required topical paromomycin. Combining these cases with guidelines and our literature review, we suggest that (i) higher doses (10-12 mg/kg/day) of fluconazole should be considered in young children to maximize likelihood and rapidity of response and (ii) patients should transition to alternate agents if they do not respond to high-dose fluconazole within 6 weeks. Furthermore, and of particular interest to the broad microbiology community, we used samples from these cases as a proof of concept to propose a mechanism to strain-type US-endemic L. mexicana. For our analysis, we sequenced three housekeeping genes and the internal transcribed sequence 2 of the ribosomal RNA gene. We identified genetic changes that not only allow us to distinguish US-based L. mexicana strains from strains found in other areas of the Americas but also establish polymorphisms that differ between US isolates. These techniques will allow documentation of genetic changes in this parasite as its range expands. Hence, our cases of cutaneous leishmaniasis provide significant evolutionary, treatment, and public health implications as climate change increases exposure to formerly tropical diseases in previously non-endemic areas.

IMPORTANCE

Leishmaniasis is a parasitic disease that typically affects tropical regions worldwide. However, the vector that carries Leishmania is spreading northward into the United States (US). Within a 6-month period, three young cutaneous leishmaniasis patients were seen at the Pediatric Infectious Diseases Clinic at the University of Texas Southwestern Medical Center/Children's Health Dallas. None had traveled outside of northern Texas and southern Oklahoma. We document their presentations, treatments, and outcomes and compare their management to clinical practice guidelines for leishmaniasis. We also analyzed the sequences of three critical genes in Leishmania mexicana isolated from these patients. We found changes that not only distinguish US-based strains from strains found elsewhere but also differ between US isolates. Monitoring these sequences will allow tracking of genetic changes in parasites over time. Our findings have significant US public health implications as people are increasingly likely to be exposed to what were once tropical diseases.

Cutaneous Leishmania mexicana Infections in the United States: Defining Strains Through Endemic Human Pediatric Cases in Northern Texas

Over a six-month span, three patients under five years old with cutaneous leishmaniasis presented to the Pediatric Infectious Diseases Clinic at the University of Texas Southwestern Medical Center/Children's Health Dallas. None had traveled outside of the United States (US); all had confirmed L. mexicana infections by PCR. We provide case descriptions and images to increase the awareness of this disease among US physicians and scientists. Two patients responded to fluconazole, but one required topical paromomycin. Combining these cases with guidelines and our literature review, we suggest that: 1) higher doses (ten-twelve mg/kg/day) of fluconazole should be considered in young children to maximize likelihood and rapidity of response and 2) patients should transition to alternate agents if they do not respond to high-dose fluconazole within six weeks. Furthermore, and of particular interest to the broad microbiology community, we used samples from these cases as a proof-of-concept to propose a mechanism to strain-type US-endemic L. mexicana. For our analysis, we sequenced three housekeeping genes and the internal transcribed sequence 2 of the ribosomal RNA gene. We identified genetic changes that not only allow us to distinguish US-based L. mexicana strains from strains found in other areas of the Americas, but also establish polymorphisms that differ between US isolates. These techniques will allow documentation of genetic changes in this parasite as its range expands. Hence, our cases of cutaneous leishmaniasis provide significant evolutionary, treatment and public health implications as climate change increases exposure to formerly tropical diseases in previously non-endemic areas.

Pharmacokinetic, efficacy, and safety considerations for the use of antifungal drugs in the neonatal population

INTRODUCTION

Invasive fungal infections are an important cause of morbidity and mortality in infants, particularly in extreme prematurity. Successful systemic treatment requires consideration of antifungal efficacy, safety, and pharmacokinetics, including optimization of dosing in this population.

AREAS COVERED

This review summarizes published pharmacokinetic data on four classes of antifungal agents used in the neonatal population. Alterations in absorption, distribution, drug metabolism and clearance in infants compared to adult populations are highlighted. Additionally, pharmacodynamics, safety, and therapeutic drug monitoring are discussed. Recent advancements in neonatal antifungal pharmacotherapies are examined, with emphasis on clinical application.

EXPERT OPINION

Over the last two decades, published studies have provided increased knowledge on pharmacokinetic considerations in the neonatal population. Future research should focus on filling in the knowledge gaps that remain regarding the benefits and risks of combination antifungal therapy, the rising use of micafungin for invasive candidiasis given its fungicidal activity against polyene and azole-resistant Candida species and its minimal adverse effect profile, and the need for pharmacokinetic and safety data of broad spectrum triazoles, like voriconazole and posaconazole, in infants. Furthermore, efforts should focus on well-designed trials, including population pharmacokinetic studies, to develop dosing recommendations with subsequent implementation into clinical practice.

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.

Cryptococcal Meningitis Presenting as a Complication in HIV-infected Children: A Case Series From Sub-Saharan Africa

Cryptococcal meningitis is a leading infectious disease worldwide as a result of the high burden of HIV and AIDS, although its cumulative incidence is very low in children compared with that in adults. Very few studies involving the disease in children have been reported including sub-Saharan Africa, with the highest prevalence of HIV-infected children in the world. We summarize 5 cases of children diagnosed with cryptococcal meningitis at a tertiary hospital in Harare, Zimbabwe, between October 1, 2013, and September 30, 2014.

First dose in neonates: are juvenile mice, adults and in vitro-in silico data predictive of neonatal pharmacokinetics of fluconazole

BACKGROUND AND OBJECTIVES

Selection of the first-dose-in-neonates is challenging. The objective of this proof-of-concept study was to evaluate a pharmacokinetic bridging approach to predict a neonatal dosing regimen.

METHODS

We selected fluconazole as a paradigm compound. We used data from studies in juvenile mice and adults to develop population pharmacokinetic models using NONMEM. We also develop a physiologically-based pharmacokinetic model from in vitro-in silico data using Simcyp. These three models were then used to predict neonatal pharmacokinetics and dosing regimens for fluconazole.

RESULTS

From juvenile mice to neonates, a correction factor of maximum lifespan potential should be used for extrapolation, while a "renal factor" taking into account renal maturation was required for successful bridging based on adult and in vitro-in silico data. Simulations results demonstrated that the predicted drug exposure based on bridging approach was comparable to the observed value in neonates. The prediction errors were -2.2, +10.1 and -4.6 % for juvenile mice, adults and in vitro-in silico data, respectively.

CONCLUSION

A model-based bridging approach provided consistent predictions of fluconazole pharmacokinetic parameters in neonates and demonstrated the feasibility of this approach to justify the first-dose-in-neonates, based on all data available from different sources (including physiological informations, preclinical studies and adult data), allowing evidence-based decisions of neonatal dose rather than empiricism.

Complicated and protracted cryptococcal disease in HIV-infected children

We report 7 HIV-infected children with cryptococcosis. Median age and CD4 counts were 9.3 years and 12 cells/mm, respectively. Two children died early. Of 4 children requiring prolonged amphotericin B and fluconazole at a dosage above 12 mg/kg/d, 3 presented with meningitis and 1 with fever. Immune reconstitution inflammatory syndrome contributed to morbidity through exacerbations at the primary site and elsewhere.

Micafungin in premature and non-premature infants: a systematic review of 9 clinical trials

BACKGROUND

Invasive fungal infections cause excessive morbidity and mortality in premature neonates and severely ill infants.

METHODS

Safety and efficacy outcomes of micafungin were compared between prematurely and non-prematurely born infants <2 years of age. Data were obtained from all completed phase I-III clinical trials with micafungin that had enrolled infants (<2 years of age) that were listed in the Astellas Clinical Study Database. Demographics, adverse events, hepatic function tests and treatment success data were extracted and validated by the Astellas biostatistical group for all micafungin-treated patients, <2 years of age, using the unique patient identifier.

RESULTS

One-hundred and sixteen patients included in 9 clinical trials, 48% premature [birth weight (BW) <2500 g and/or gestational age <37 weeks], 52% non-premature, received ≥ 1 dose of micafungin. Among premature patients, 14.5% were low BW (1500-2499 g), 36.4% very low BW (1000-1499 g) and 49.1% extremely low BW (<1000 g). Ninety patients (78%) completed the studies; 13 [11% (4 premature)] died. Significantly more non-premature than premature patients discontinued treatment (P = 0.003). Treatment-related adverse events were recorded in 23% of patients with no difference between groups. More extremely low BW (n = 4, 15%) and very low BW (n = 8, 40%) infants experienced treatment-related adverse events than low BW (n = 0) and there was no relation to micafungin dose or duration. For a subgroup of 30 patients with invasive candidiasis, treatment success was achieved in 73% in both premature and non-premature groups. Prophylaxis was successful in 4/5 non-premature hematopoietic stem cell transplant patients.

CONCLUSION

Micafungin has a safe profile in premature and non-premature infants with substantial efficacy.

The use of antifungal therapy in neonatal intensive care

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