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  Pharmacology (Greek, ‘study of potions’) is the study of the effect of chemical substances (drugs) on physiological systems. It is chiefly a 20th-century development because of the biochemical level at which drugs act. One of the founding figures in pharmacology was François Magendie who published his Formulary in 1821. He investigated the activity of a number of drugs as pure substances, representing a departure from the practice of prescribing complex mixtures of drugs. The Roman physician Galen (129 - 200 CE) had ascribed properties to various drugs, predominantly botanical in origin, but he prescribed them as mixtures. This practice endures to this day and gives rise to numerous popular, frequently useless or dangerous, ‘cure-all’ mixtures.

In the 19th century, chemists such as Oswald Schmiedeberg began to study the effects of various drugs upon physiology, and it is now routine to perform a wide range of pharmacological studies before a new drug is licensed for use. Paul Ehrlich (1857 - 1915) proposed that chemicals might be used to treat disease and some of the first examples of this new ‘chemotherapy’ were chemicals derived from the dye industry. By a process of selective variation of chemical structure these drugs were modified and tested and gradually improved. Substances derived from plants were chemically synthesized and modified in a similar fashion to produce the range of drugs in use today. Most new drug development continues by this process of trial and error, though the new technologies of biophysics and molecular biology present the possibility of designing drugs to combat specific diseases.

Drugs act on the metabolism of the individual or the metabolism of pathogenic organisms which infect the individual. Frequently a single drug affects more than one biological system and two or more drugs together may act synergistically or antagonistically. It is thus vital to carry out comprehensive testing of drugs before they are used for medical or veterinary purposes. The testing typically follows a hierarchical system of simple screening, leading on to more complex and costly testing on animals and finally trials in humans. The study of the effect of drugs at various doses under various conditions is called pharmacodynamics, while biochemical pharmacology involves the study of the action of drugs on the metabolism. RB

See also psychopharmacology; toxicology.Further reading B.G. Katzung, Basic and Clinical Pharmacology.



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