Pragmatic modeling supports current dosing guidelines for carbamazepine and valproic acid for the treatment of epilepsy in children

BackgroundCarbamazepine (CBZ) and valproic acid (VPA) are long-standing treatments for epilepsy in children. Interestingly, they display unique drug disposition characteristics and maturation of drug metabolizing enzymes further complicates personalized dosing. Physiologically-based pharmacokinetic (PBPK) modeling includes these mechanisms and is hence a promising tool to optimize dosing. Our aim is to better support pediatric drug dosing of CBZ and VPA. MethodsAll CBZ and VPA dosing simulations were conducted with Simcyp, using available CBZ and VPA compound models linked with adult and pediatric population models. Current Dutch national dosing strategies were simulated to evaluate their appropriateness to achieve therapeutic levels. Where doses could be optimized, alternative dosing strategies were proposed based on simulations. ResultsTherapeutic levels of CBZ and VPA will be reached after 1 or 2 weeks of treatment with the current dosing strategies. Simulations suggest a CBZ starting dose of 7 mg/kg/day for neonates rather than 10 mg/kg/day. In contrast, children aged 12 to 18 years may receive a higher starting dose (e.g., 400 mg/day instead of 200 mg/day), to reach therapeutic levels more quickly. For VPA, when higher doses are needed (i.e., [≥]30 mg/kg/day), measuring unbound VPA concentrations are advised to guide dosing. ConclusionWe demonstrate that PBPK modeling is a valuable tool to confirm and further optimize dosing recommendations in children. The use of PBPK modeling offers a practical, cost-effective, and swift method to provide valuable comprehensive evidence for guiding clinical practice and potentially informing pediatric drug labeling, thus eliminating the necessity for clinical studies.