Evaluation of the predictive performance of a pharmacokinetic model for propofol in Japanese macaques (Macaca fuscata fuscata)

Propofol is a short-acting intravenous anesthetic used for induction/maintenance anesthesia. The objective of this study was to assess a population pharmacokinetic (PPK) model for Japanese macaques during a step-down infusion of propofol. Five male Japanese macaques were immobilized with ketamine (10mg/kg) and atropine (0.02mg/kg). A bolus dose of propofol (5mg/kg) was administrated intravenously (360mg/kg/h) followed by step-down infusion at 40mg/kg/h for 10min, 20mg/kg/h for 10min, and then 15mg/kg/h for 100min. Venous blood samples were repeatedly collected following the administration. The plasma concentration of propofol (Cp) was measured by high-speed LC-FL. PPK analyses were performed using NONMEM VII. Median absolute prediction error and median prediction error (MDPE), the indices of prediction inaccuracy and bias, respectively, were calculated, and PE-individual MDPE vs. time was depicted to show the variability of prediction errors. In addition, we developed another population pharmacokinetic model using previous and current datasets. The previous PK model achieved stable prediction of propofol Cp throughout the study period, although it underestimates Cp. The step-down infusion regimen described in this study would be feasible in macaques during noninvasive procedures.