Data from 104 pediatric SOT recipients (kidney, liver, and heart) aged 0.3-16.9 yr and receiving v-GCV once a day were used for model development and validation with the Pmetrics package for R. Monte Carlo simulations were performed to compare the probability of a GCV AUC 40-60 mg*h/L with the different algorithms across a range of ages, weights, and GFRs. 
Pmetrics
New algorithm for valganciclovir dosing in pediatric solid organ transplant recipients.CMV infections are common after SOT.  v-GCV is increasingly used in children.  The aim of this study was to evaluate presently used dosing algorithms.  Data from 104 pediatric SOT recipients (kidney, liver, and heart) aged 0.3-16.9 yr and receiving v-GCV once a day were used for model development and validation with the Pmetrics package for R. Monte Carlo simulations were performed to compare the probability of a GCV AUC 40-60 mg*h/L with the different algorithms across a range of ages, weights, and GFRs.  GCV pharmacokinetics was well described by the non-parametric model.  Clearance was dependent on GFR and Cockcroft-Gault estimates improved the model fit over Schwartz.  Simulations showed that our new algorithm, where v-GCV dose is: Weight [kg]*(0.07*GFR [mL/min]+k), where k = 5 for GFR ≤ 30 mL/min, k = 10 for GFR > 30 mL/min and weight > 30 kg and k = 15 for GFR > 30 mL/min and weight ≤ 30 kg, outperformed the other algorithms.  Thirty-three percent of all patients achieve an exposure above and 21% within the therapeutic window.  We propose a simple algorithm for initial v-GCV dosing that standardizes plasma drug exposure better than current algorithms.  Subsequent TDM is strongly suggested to achieve individual drug levels within the therapeutic window.
R