Anidulafungin: is it a promising option in the treatment of pediatric invasive fungal infections?

Chromatographic methods for echinocandin antifungal drugs determination in bioanalysis

The increase of fungal resistance to drugs, such as azole family, gave rise to the development of new antifungals. In this context, echinocandins emerged as a promising alternative for antifungal therapies. Following the commercialization of caspofungin in 2001, echinocandins became the first-line therapy for invasive candidiasis in different patient populations. The quantification of these drugs has gained importance since pharmacokinetic/pharmacodynamic and resistance studies are a paramount concern. This fact has led us to exhaustively examine the methodologies used for the analysis of echinocandins in biological fluids, which are mainly based on LC coupled to different detection techniques. In this review, we summarize the analytical methods for the quantification of echinocandins focusing on sample treatment, chromatographic separation and detection methods.

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.

Invasive fungal infections in infants-focus on anidulafungin

Introduction:

Invasive fungal infection in pediatric intensive care units (PICU) is a rising challenge. Candida species are the most common microorganisms in these infections. Due to growing resistance against fluconazole, echinocandins are being used for the appropriate therapy. However, the recent IDSA guidelines recommend them only in cases where fluconazole or Amphotericin B cause treatment failure or are contraindicated. In a literature review, the importance of invasive fungal infections in PICU settings and the role of anidulafungin shall be examined.

Materials and Methods:

Articles were retrieved form PubMed covering the years 2000–2012. Various search terms were used. Then the articles were clustered in different types like ‘review,’ ‘pharmacokinetics,’ ‘case reports’ and others.

Results:

From 67 search results, 14 articles were selected. Of these, 7 were related to anidulafungin, while 7 were related to echinocandins or fungal infections in the PICU. Anidulafungin was examined in 4 PK/PD studies where a good safety profile was found. No serious adverse events occurred. The articles reporting risk factors show that central venous catheters, receipt of antibiotics, receipt of parenteral nutrition, and neutropenia are the most important independent risk factors for invasive fungal infections in PICU. Three reviews of antifungal agents show that echinocandins may be useful due to their safety profile; micafungin is the best examined one and further trials are needed.

Discussion:

The published literature on invasive fungal infections in PICU settings has grown over the years. There are only a few articles, however, which are directly related to the use of anidulafungin in this setting. A most recent publication showed good PK/PD dynamics and a good safety profile for anidulafungin. So far, no RCT in the area of invasive candidiasis in infants and neonates has been published. A review of currently registered trials at ClinicalTrials.gov has shown one more trial related to PK/PD and two trials that investigate the use of anidulafungin or anidulafungin in combination with Voriconazole in pediatrics.

Conclusion:

The small body of existing literature on anidulafungin in infants shows success in treatment, no drug-related adverse events, and good pharmacodynamics. A dosing of 0.75 mg/kg/day or 1.5 mg/kg/day is as effective as 50 mg/day or 100 mg/day in adults. More trials on the use in clinical reality of PICU or NICU should follow.