Posaconazole therapeutic drug monitoring in pediatrics: a single-center retrospective study

BACKGROUND: Invasive fungal infections are associated with high morbidity and mortality in immunosuppressed pediatric patients. Posaconazole is commonly used for both prophylaxis and treatment of invasive fungal infections. The study's primary objective was to determine the percentage (%) of patients that achieved posaconazole therapeutic targets. The secondary objective was to evaluate the relationship between posaconazole exposure and clinical outcomes or toxicity. METHODS: This single-center retrospective study included pediatric patients from 1 month to 18 years who received posaconazole for prophylaxis fungal infections. Data were collected from the hospital's electronic medical records and included age, gender, height, weight, laboratory values, dose, dosing frequency, trough concentrations, drugs interact with posaconazole. Primary outcomes included the percentage of patients who achieved target trough levels of posaconazole. We also looked at factors correlated to trough concentrations, which included: dose, age, weight, presence of drug interactions and laboratory values such aspartate transaminase (AST), alanine transaminase (ALT), and albumin levels. Secondary outcomes included the correlation between posaconazole trough concentrations, clinical or microbiologic outcomes, and toxicity. RESULTS: A total of 69 trough plasma concentrations were measured across 42 patients. Among these, 27 patients had a second trough level assessed. The mean concentration of the initial trough was 1.4 ± 1.3 mg/L (mean ± SD), with concentrations ranging from 0.2 to 6.2 mg/L. The mean concentration of the second trough was 0.99 ± 0.8 mg/L, ranging from 0.2 to 4.1 mg/L. For the initial trough concentrations, 59.5% fell within the therapeutic range. A total of 10 patients (23.8%) experienced adverse events that were attributed to posaconazole. CONCLUSION: Posaconazole trough concentrations vary in pediatric patients and around half of the patients achieved therapeutic concentrations with initial doses with minimal adverse events reported.