Definition of Pharmacodynamics
Pharmacodynamics is the study of the biochemical and physiological effects of drugs on the body or on microorganisms or parasites within or on the body and the mechanisms of drug action and the relationship between drug concentration and effect.
Pharmacodynamics is often summarized as the study of what a drug does to the body. The effects of most drugs result from their interaction with macromolecular components of the organism.
These interactions alter the function of the pertinent component and thereby initiate the biochemical and physiological changes that are characteristic of the response to the drug.