ABSTRACT
. Physiological models, in contrast to the traditional compartmental models, are based on an understanding of the actual anatomical and physiological factors which dictate xenobiotic disposition. This chapter illustrates role of pharmacokinetics in the rationalization of target organ toxicity using the constant exposure model. There are many macromolecules within the blood which are capable of reversibly binding xenobiotics. The rates of association and dissociation between compounds of low molecular weight and macromolecules are usually rapid. An additional complication in the assessment of xenobiotic uptake into a particular tissue exists when that tissue can eliminate xenobiotic from the body. Classifying hepatic metabolism of drugs in terms of their extraction ratio has proved useful. The concentration of xenobiotic in the circulating fluids is dependent upon the amount of xenobiotic in the body and the extent of tissue distribution.
