Pharmacology, a term derived from the Greek word pharmakon ("medicine"), may be broadly defined as the study of drugs. The
study includes three major and intimately related disciplines: toxicology,
pharmacodynamics, and therapeutics, each of which has developed into a specialized area of study. In a restricted sense,
pharmacology and pharmacodynamics are used synonymously and include the study of the biochemical and physiological effects of drugs on a living organism, from their administration, absorption, and distribution to their metabolism and excretion. The mechanism by which the drugs produce their effects is also studied. Therapeutics considers the use of drugs in the prevention, diagnosis, and treatment of disease.
Pharmacology as an experimental science began in the 19th century with the work of Franois Magendie, who studied the mechanism of absorption and distribution of drugs in the human body and their localization at the site of their action. Since that time a close relationship has existed in the fields of chemistry, physiology, pathology, and microbiology to study drug action.