Many statements in pharmacological literature imply that most drugs exert invariable effects. When differences in the effects of administering the same amount of a drug to different patients have occurred, they have usually been ascribed to "idiosyncratic" reactions. This is undoubtedly true in the case of those persons who consistently display an unusual reaction to a drug regardless of the conditions under which it is administered. However, the concept of "idiosyncrasy" cannot explain the commonly observed clinical fact that some drugs exert widely different effects upon the same patient in different situations.
The popular description of drugs as either "stimulant" or "depressant," in view of such variability, appears to stem from two sources. One is the information about drug actions, which has been obtained largely in the course of treatment of patients in the relatively standardized situation of the general hospital. The other is knowledge obtained in the laboratory. On
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