2.3 Model distribution
An illustration of the pregnancy PBPK model is shown on Figure 1. A fetal component within the female reproductive organ was not included within this pregnancy PBPK model as the main focus on this study was the PK in the pregnant woman and not fetal exposure. Major assumptions in the PBPK model include perfusion-limited drug distribution, well-stirred distribution model, and no drug reabsorption from the colon. The volume of drug distribution (Vd) was calculated from the volume and tissue-to-plasma ratio of each compartment as previously described [38]. Pregnancy effect on the fraction of the unbound drug was also modelled using equations previously described in literature [23, 39]. Lastly, activity of drug transport­­ers were not included in the model due to inadequate data for such characterisation.