ABSTRACT
It has been recognized for many years1 that the relationship between drug administration and therapeutic response can be subdivided into two aspects:
1. Pharmacokinetics, which relates to the movement of the drug within the body
2. Pharmacodynamics, which is concerned with the pharmacological effects once the drug is delivered to its site of action/receptor
The principles of pharmacokinetics apply to any environmental nonnutrient (xenobiotic), and many of the biological processes involved in the absorption, distribution, and elimination, such as the metabolizing enzymes, are nonspeci•c and shared by drugs and other low-molecularweight organic molecules such as additives, pesticides, and contaminants. The term toxicokinetics is now widely accepted to describe pharmacokinetic processes for potentially toxic chemicals, which do not have a therapeutic effect. Toxicokinetics is the application of pharmacokinetic principles to animal toxicity studies and to human toxicity data, in order to provide information on internal exposure to the parent compound and its metabolites, and other aspects such as accumulation during chronic exposure.
