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.