Population Pharmacokinetic/Pharmacodynamics Modeling of Ibutilide in Chinese Healthy Volunteers and Patients With Atrial Fibrillation (AF) and/or Atrial Flutter (AFL).

The goal of this study was to develop a population pharmacokinetic (PK) and PK/pharmacodynamics (PD) model for ibutilide, to evaluate the time course of its effect on QT interval in Chinese.The population PK and PK/PD model were developed using data from 40 Chinese healthy volunteers using nonlinear mixed-effects modeling, and the final population PK/PD model was applied on 100 patients with atrial fibrillation (AF) and/or atrial flutter (AFL).The PK parameters of ibutilide were best described by a 3-compartment model with first-order elimination. No statistically significant covariate was found for each PK model parameter. Individualized QT interval correction, by heart rate, was performed by a power model, and the circadian rhythm of QT intervals was described by 2 mixed-effect cosine functions. The QT interval data of ibutilide was well characterized by a sigmoid Emax model (E(C)=Emax(γ)×C(γ)/(EC50(γ)+C(γ))) with an effect compartment. The final PK/PD model was used to estimate individual parameters of patient data and found good predictions compared with healthy volunteers; AF and/or AFL patients had lower Emax and higher EC50.A population PK and PK/PD model for ibutilide in healthy volunteers was developed and could well capture ibutilide's PK/PD characteristics. The final PK/PD model was applied on patients with AF and/or AFL successfully.