[General conceptions of pharmacokinetics: physiological and mathematical approaches].

Intensity and duration of drug effects depend upon both their pharmacodynamic and pharmacokinetic properties. The former characterize the potential intrinsic activity of the molecule and are dependent upon its ability to modulate, stimulate or inhibit a biological system. The latter control the amount and time during which the drug is present at the site of action. During the last few years, pharmacokinetics have developed in two directions: first, the recognition of the physiological mechanisms responsible for the drug disposition; second, the quantitative analysis of the fate of the drug concentrations using mathematical models. These models have become more and more sophisticated, and now include a physiological approach.