Renal maturation and catch-up clearance of ganciclovir in a preterm neonate: Bayesian pharmacokinetic analysis using a population model

Abstract Background Congenital cytomegalovirus (CMV) infection is a major cause of neonatal morbidity. However, optimizing ganciclovir (GCV) dosing in preterm infants is complicated by immature renal function and developmental pharmacokinetics. Population pharmacokinetic (PPK) parameters for GCV and valganciclovir (VGCV) have been reported, but data remain limited for extremely low birth weight infants. We aimed to characterize longitudinal changes in GCV clearance in a preterm infant with congenital CMV infection using Bayesian modeling. Methods GCV/VGCV were administered over a 15-week period, with concurrent therapeutic drug monitoring. Individual parameters were estimated using a previously published PPK model and a postnatal age-based maturation function in NONMEM. Scr clearance was measured at two time points using the 24-h urine collection method. Results GCV clearance increased from 0.048 to 0.273 L/hr/kg from postnatal day 30 to day 93, whereas VGCV bioavailability remained stable (~ 52–55%). Scr clearance values matched estimated GCV clearance, supporting the validity of the model. The maturation function indicated that tubular secretion likely contributes to accelerated drug elimination. Late-phase GCV clearance exceeded typical glomerular filtration rate, indicating possible catch-up in renal function. Conclusion Renal maturation should be considered in addition to body weight when adjusting GCV dosing in preterm infants. This case highlights the importance of aligning individualized dosing strategies with the developmental physiology of preterm neonates.