Principles of Pharmacokinetics and Pharmacodynamics: Introduction | Pharmacokinetics | Pharmacodynamics | Variability in the Dose–Effect Relationship | Conclusion | References
defined as the study of the time course of drugs and their metabolites
through the body. Pharmacodynamics is
defined as the study of the time course and intensity of pharmacological
effects of drugs. A convenient lay description of these terms is
that pharmacokinetics describes what the body's physiology
does to a drug, and pharmacodynamics describes what a drug does
to the body. Although clinicians are more interested in drug effects
than drug concentrations, these disciplines are closely connected.
Pharmacokinetic and pharmacodynamic variability is a major determinant
of the dose–effect relationship in patients (Figure 8–1).
There is increasing recognition that genetic variability—in
the form of polymorphic genes controlling the transcription of proteins
involved in drug-metabolizing enzymes, drug transporters, and drug
targets—is a substantial determinant of pharmacokinetic
and pharmacodynamic variability. An integrated knowledge of these
areas is essential in the drug development process and can be instrumental
in individualizing dosage regimens for specific patients.