ABSTRACT
The action of a drug, when administered to animals or humans, is usually divided into two phases: the pharmacokinetic phase and the pharmacodynamic phase [1]. The pharmacokinetic phase comprises all processes of absorption, distribution, metabolism, and clear-ance [2]. The pharmocodynamic phase includes all biological processes involved in the interaction of the drug with its target (receptor, enzyme, etc.) [3]. In other words, the pharmacokinetic phase is concerned with the effects exerted by a drug upon a biological system, whereas the pharmacodynamic phase represents the effects exerted by a biological system upon a drug [4, 5]. It is the balance of the performances of a compound in these two phases that determines the success of a drug.
