Valganciclovir Dosing for Cytomegalovirus Prophylaxis in Pediatric Solid-organ Transplant Recipients: A Prospective Pharmacokinetic Study

Background: Valganciclovir is extensively used for prophylaxis and treatment of cytomegalovirus (CMV) infection in solid-organ transplant recipients. However, pharmacokinetic data in children are scarce, and the pediatric dosing regimen is uncertain. This study sought to prospectively evaluate the pharmacokinetic profile, the clinical efficacy and safety of oral valganciclovir in pediatric transplant recipients and compare different dosing regimens. Methods: The cohort included solid-organ transplant recipients treated with valganciclovir for CMV prophylaxis in 2014-2015 at a tertiary pediatric medical center. All received a weight-based once-daily oral dose of 17 mg/kg. Ganciclovir concentrations were measured and the area under the curve (AUC^0-24) was calculated. Results: Thirteen children of median age 7.3 years (interquartile range, 2.2-11.6) were included. Median ganciclovir AUC^0-24 was 21.0 mcg·h/mL (interquartile range, 17.1-39.8); 10 patients (77%) attained AUC^0-24 <40 mcg·h/mL. Exposure to ganciclovir was about 2-fold lower in young children (<9 years old; P = 0.01) and children with low body surface area (BSA; <0.7 m²; P = 0.006) than in their counterparts. Significantly lower doses were recommended with our weight-based protocol than with the manufacturer-recommended BSA-and glomerular filtration rate-based protocol (P = 0.002), reaching a 3-fold difference in infants. No evidence of CMV viremia or disease was observed while prophylaxis was given. Conclusions: The weight-based regimen of 17 mg/kg/dose oral valganciclovir results in relatively low ganciclovir exposure, especially in young children with low BSA, yet showed satisfactory clinical efficacy for CMV prophylaxis. The manufacturer's dosing recommendation appears to result in supratherapeutic ganciclovir concentrations. Further studies are needed to establish target AUCs and valganciclovir dosing for CMV prophylaxis in pediatric transplant recipients.