Fluconazole in neonatal disseminated candidiasis

Developmental changes of fluconazole clearance in neonates and infants in relation to ontogeny of glomerular filtration rate: literature review and data analysis

BACKGROUND

Fluconazole is frequently prescribed for the treatment of systemic fungal infection in neonates and infants. At present, prediction of fluconazole doses according to developmental changes in fluconazole clearance is not being done in these patients. We aimed to formulate a developmental model of fluconazole clearance taking into account the ontogeny of renal function, since the drug is largely eliminated renally.

METHODS

We systematically retrieved the data of fluconazole pharmacokinetics and renal function in children and adults from databases (MEDLINE and Japan Medical Abstracts Society). Datasets were retrieved from individual children or groups from 9 studies comprising 55 neonates or infants at postmenstrual age (PMA) 27-58 weeks. Datasets were retrieved from 5 studies comprising 60 children and from 13 studies comprising 152 adults. Datasets of glomerular filtration rate (GFR) for individual pediatric subjects were retrieved from 4 studies comprising 187 neonates or infants.

RESULTS

Fluconazole clearance normalized to body surface area (BSA) (CLBSA) in neonates was 1/3 to 1/4 of adult values, but CLBSA increased rapidly during the neonatal and infantile periods and attained near adult values at PMA 60 weeks. A significant correlation between CLBSA and PMA was observed in neonates and infants: CLBSA (mL/min/m2) = 0.26・ PMA (weeks) - 4.9 (r = 0.68, p < 0.001). In addition, the developmental time course of GFR normalized to BSA (GFRBSA) was fitted well to a sigmoidal model with the maximum GFRBSA of 149 mL/min/1.73m2, PMA associated with 50% of GFRBSA,max (PMA50) of 54 weeks, and the Hill coefficient of 3.7. A significant correlation between fluconazole clearance and GFR was found in neonates and infants: CL (mL/min) = 0.34・GFR (mL/min) - 0.53 (r = 0.84, p < 0.001). Assuming that plasma drug concentrations required for treating fungal infection are comparable between children and adults, fluconazole doses for pediatric patients with given PMAs may be predicted from adult doses (such as 100 mg/day) using size-normalized clearance as a scaling factor. The predicted doses for neonates and infants were largely within the ranges recommended in the prescribing information.

CONCLUSIONS

The present study indicates that fluconazole doses for neonates and infants may be predicted from developmental change of systemic clearance, the ontogeny of which parallels the maturation of nephron function.

Antifungals in systemic neonatal candidiasis

Fungal infections are common in the newborn period, especially among premature neonates, and are responsible for considerable morbidity and mortality. Currently, three classes of antifungals are commonly used in the treatment of systemic fungal infections in neonates: the polyene macrolides (e.g. amphotericin B [deoxycholate and lipid preparations]); the azoles (e.g. fluconazole); and the fluorinated pyrimidines (e.g. flucytosine). The echinocandins (e.g. caspofungin and micafungin) are a newer class of antifungals which shows promise in this population.The available kinetic data on amphotericin B deoxycholate in neonates are derived from very small studies and exhibit considerable variability. There are no kinetic data available for the use of lipid preparations in this population and, again, much has been inferred from adult studies. The information available for flucytosine is also limited but appears similar to what is observed in adults. Fluconazole has the most neonatal pharmacokinetic data, which show slightly less variability than the other antifungals. Genomic factors which affect the metabolism of amphotericin B and fluconazole may explain some of the observed variability. Most of the data for the efficacy of antifungal drugs in neonates are derived from retrospective studies and case reports. The data for amphotericin B deoxycholate and flucytosine are limited. There are more data for the liposomal and lipid complex preparations of amphotericin B and for fluconazole in this population. These support the use of these drugs in neonates, but because of their largely noncomparative nature they can not define the optimal dosage or duration of therapy. Amphotericin B deoxycholate is primarily nephrotoxic. It also induces electrolyte abnormalities and is to a lesser degree cardiotoxic. This toxicity in neonates appears similar to published data in older children and adults. While the lipid preparations of amphotericin B owe their existence to a presumed decrease in toxicity, the observed toxicity in neonates appears to be equal to that seen with the deoxycholate, although it should be noted that the lipid preparations are usually given at much higher dosages. Fluconazole toxicity appears to be milder and less frequent in this population than is seen with amphotericin B. In the final analysis, we do not have sufficient data to define the pharmacokinetic profiles, optimal dose or duration of therapy, or toxicity for any of these compounds in neonates. Further studies are necessary if the optimisation of antifungal therapy in this population is to continue.

Administration of fluconazole in children below 1 year of age

For this review, 78 studies regarding the use of fluconazole in a total of 726 children below 1 year of age were evaluated. The range of fluconazole dosage was 2-50 mg kg-1 day-1, with 162 days being the maximum duration of treatment. According to current experience, fluconazole seems to be well tolerated and efficacious against systemic candidosis and candidaemia in children below 1 year of age, including neonates and very low-birthweight infants (VLBWIs). The recommended daily dosage is 6 mg kg-1. (In Germany, fluconazole is approved for children between 1 and 16 years in cases in which there is no therapeutic alternative for treatment of systemic infections caused by Candida spp. and Cryptococcus neoformans in a dosage of 3-6 mg kg-1 day-1 and for superficial Candida infections in a dosage of 1-2 mg kg-1 day-1.) In patients with impaired renal function, the daily dose should be reduced in accordance with the guidelines given for adults. In neonates during the first 2 weeks of life, this dosage should be administered only every 72 h. In weeks 2-4 of life, the same dose should be given every 48 h, following which daily dosing is appropriate. This posology is derived from the age-related pharmacokinetics of fluconazole, with a higher volume of distribution and a prolonged plasma elimination half-life, especially during the first month of life. Drug monitoring during treatment should be performed to ensure therapeutic plasma concentrations of fluconazole within a range between 4 and 20 micrograms ml-1. The benefit of fluconazole should be investigated in prospective studies for treatment of systemic candidosis with administration of higher dosages as well as for early empiric therapy in VLBWIs.

[Use of fluconazole in children less than 1 year old: review]

For this review, 78 publications for use of fluconazole in children below 1 year of age were evaluated with a total of 726 patients. The range of fluconazole dosage was 2-50 mg/kg/day with 162 days as maximum duration of treatment. According to the present experience, fluconazole seems to be an efficacious and well tolerated therapy against systemic candidosis and candidemia in children below 1 year of age, including neonates and very low birth-weight infants (VLBWI). The recommended daily dosage is 6 mg/kg. In patients with impaired renal function, the daily dose should be reduced in accordance with the guidelines given for adults. In neonates during the first two weeks of life, this dosage should be administered only every 72 hours. In weeks two to four of life, the same dose should be given every 48 hours. After that daily dosing is appropriate. This posology is derived from the age-related pharmacokinetics of fluconazole with a higher volume of distribution and a prolonged plasma elimination half life especially during the first month of life. Drug monitoring during treatment should be performed to ensure therapeutic plasma concentrations of fluconazole within a range between 4 and 20 micrograms/ml. The benefit of fluconazole should be investigated in prospective studies for treatment of systemic candidosis with administration of higher dosages as well as for early empiric therapy in VLBWI.

Fluconazole

Incidence of systemic candidiasis is increasing with improvement in the survival of high risk neonates who undergo multiple interventions. Therapies available to treat systemic fungal infection are few and have several drawbacks. Fluconazole, a new triazole derivative may be a useful anti-fungal agent in view of its excellent oral absorption, easy administration, low plasma protein affinity, long half-life, high concentrations in urine and CSF, minimal adverse reactions, wide spectrum of anti-fungal activity and high specificity for fungal cytochrome P450 system. Its utility in neonates and children with candidiasis has already been documented by few case reports and studies.

Neonatal renal candidiasis

A case is presented of renal candidiasis complicated by obstructive uropathy in a 4 month old infant. Management was successful with surgical decompression combined with peri-operative amphotericin B, followed by 3 weeks of oral ketoconazole and subsequently 6 weeks of oral fluconazole. Fluconazole was substituted for ketoconazole owing to persistent candiduria, and achieved rapid urinary sterilization. Fluconazole is an effective and less toxic alternative to prolonged courses of amphotericin B in the treatment of neonatal renal candidiasis.