 Therefore, extrapolating adverse effects observed in vitro is incorporated into a quantitative model of in vivo PK model.It is generally accepted that physiologically based PK (PBPK) models, including absorption, distribution, metabolism, and excretion of any given chemical are central to "in vitro" - "in vivo" extrapolations.In the case of early effects or those without inter-cellular communications, it is assumed that the same cellular exposure concentration cause the same effects, both experimentally and quantitatively, "in vitro" and "in vivo".