Population pharmacokinetics of moxifloxacin and its concentration–QT interval relationship modeling in Chinese healthy volunteers

Moxifloxacin (MX) is an 8-methoxyquinolone antimicrobial drug, which is often used as a positive control in thorough QT (TQT) studies. In the present study we established the population pharmacokinetics model of MX and the relationship of MX concentrations with the QT and various corrected QT (QTc) intervals, and compared the results with other ethnicities. The MX data used for modeling were obtained from a published TQT interval prolongation study of antofloxacin with MX as the positive control. In this four-period crossover study, 24 adult Chinese healthy volunteers received either 200 or 400 mg of oral antofloxacin once daily, 400 mg of MX, or a placebo. Population concentration-effect models were used to investigate the relationship between MX concentrations and QT interval prolongation, baseline-adjusted QTc (ΔQTc), or ΔQTc adjusted with time-matched placebo corrections (ΔΔQTc). The influencing factors of MX PK and the concentration-QTc relationship were determined through covariate screening. Simulation studies were conducted in R2.30 by using the final model with the estimated population mean and intra-individual and inter-individual variability. The estimated pharmacokinetic parameters and the estimated slope of the MX concentration-QT/ΔQTc/ΔΔQTc relationship were described using models and were compared to results for other ethnicities from the literature. We showed that the population pharmacokinetic parameter estimates for total plasma clearance (CL/F), the volume of distribution of central compartment (Vc/F), the distributional clearance in plasma (Q), the volume of distribution of peripheral compartment (Vp/F), and the absorption rate constant (K_a) were 8.22 L/h, 104 L, 3.98 L/h, 37.7 L, and 1.81 1/h, respectively. There was no significant covariate included in the final model. QT interval prolongation of MX estimates ranging from 9.77 to 12.91 ms at the mean average maximum concentration of MX (4.36 μg/mL) and a mean slope ranging from 2.33 to 2.96 ms per μg/mL. In conclusion, no ethnic differences were observed for the MX pharmacokinetic parameters and QT interval prolongation.