Physiologically Based Pharmacokinetic Modelling - Uses of PBPK Modeling

Uses of PBPK Modeling

PBPK models are compartmental models like many others, but they have a few advantages over so-called "classical" pharmacokinetic models, which are less grounded in physiology. PBPK models can first be used to abstract and eventually reconcile disparate data (from physico-chemical or biochemical experiments, in vitro or in vivo pharmacological or toxicological experiments, etc.) They give also access to internal body concentrations of chemicals or their metabolites, and in particular at the site of their effects, be it therapeutic or toxic. Finally they also help interpolation and extrapolation of knowledge between:

• Doses: e.g., from the high concentrations typically used in laboratory experiments to those found in the environment
• Exposure duration: e.g., from continuous to discontinuous, or single to multiple exposures
• Routes of administration: e.g., from inhalation exposures to ingestion
• Species: e.g., transpositions from rodents to human, prior to giving a drug for the first time to subjects of a clinical trial, or when experiments on humans are deemed unethical, such as when the compound is toxic without therapeutic benefit
• Individuals: e.g., from males to females, from adults to children, from non-pregnant women to pregnant

Some of these extrapolations are "parametric" : only changes in input or parameter values are needed to achieve the extrapolation (this is usually the case for dose and time extrapolations). Others are "nonparametric" in the sense that a change in the model structure itself is needed (e.g., when extrapolating to a pregnant female, equations for the fetus should be added).