Voriconazole dosing and therapeutic drug monitoring in children: experience from a paediatric tertiary care centre

Objectives: Therapeutic drug monitoring (TDM) of voriconazole is recommended to achieve trough concentrations of 1-5 mg/L. In children, this is challenging due to age-related variability in voriconazole pharmacokinetics. This study describes our experience with voriconazole, focusing on dosing regimens, dose adjustment and TDM. Methods: We reviewed the medical records of immunocompromised children who received voriconazole from July 2009 to January 2015 and had TDM. Demographic, clinical and voriconazole dosing and monitoring data were collected. Results: Fifty-five children received 62 courses of voriconazole and had TDM, with a total of 256 samples taken. Only 71.0% of courses (44/62) had TDM at the correct time, and at least one therapeutic level was achieved in only 52.3% (23/44) of these. Twenty-six courses had at least one sub-therapeutic level and in only 61.5% was the dose adjusted. Patients aged <6, 6-12 and >12 years required median intravenous doses of 8.8, 7.5 and 4.0 mg/kg twice daily, respectively (P<0.001). With oral administration, patients aged 6-12 and >12 years required median doses of 4.7 and 4.3 mg/kg twice daily, respectively (P=0.307). Levels within the target range were observed to fall below 1 mg/L in 36.4% of unchanged dosing regimens. Photosensitive skin reactions (20.0%) and hepatotoxicity (12.7%) were the most frequent adverse events and occurred in children with voriconazole levels <5 mg/L. Conclusions: There is significant intra-and inter-individual variability in voriconazole concentrations in children, particularly in children,6 years of age. This warrants repeated TDM throughout treatment. Standardized guidelines for TDM and dose adjustment are required in children.