Population pharmacokinetics of oxcarbazepine 10-monohydroxy derivative in Chinese adult epileptic patients

Objective Oxcarbazepine (OXC) is metabolised to active 10-monohydroxy derivative (MHD) after oral administration. Using this fact we aimed to develop an MHD population pharmacokinetic (PPK) model in Chinese adult epileptic patients to facilitate the clinical implementation of model-guided individualised drug therapy. Methods We collected blood samples from Chinese adult epileptic patients taking OXC at the Second Affiliated Hospital of Zhejiang University School of Medicine. We used high performance liquid chromatography (HPLC-MS/MS) with tandem mass spectrometry to detect MHD concentrations in the blood samples. We collected various data from patients including their demographic, pathological, and physiological information. MassARRAY method was used to detect ABCC2, ABCB1, SCN8A, SCN1A, SCN2A, SCN3A, UGT1A9, and UGT2B7 gene polymorphisms. We used a nonlinear mixed-effects modelling method to develop the PPK model and we predicted dosing regimens through simulation. Result In total we collected 164 blood samples from 118 patients. We found that a one-compartment model with first-order absorption better described the in vivo MHD pharmacokinetics. UGT2B7 gene (rs7439366) site mutation and the combined use of valproic acid enhanced the MHD clearance rate. We divided patients into groups based on the UGT2B7 genotype and whether they were also using valproic acid at the same time. Individualised OXC dosing regimens were proposed for different subgroups of patients. Conclusion In Chinese adult epileptic patients, individualised drug administration can be facilitated using a PPK model of OXC.