The present status of tranquilzing drugs.

TRANQUILIZING DRUGS MAY BE CLASSIFIED INTO FOUR GROUPS, ACCORDING TO CHEMICAL STRUCTURE: (1) Phenothiazine derivatives, (2) Rauwolfia alkaloids, (3) substituted propanediols or butanediols, and (4) diphenylmethane derivatives. The distinguishing features of tranquilizing drugs in contrast to conventional sedatives is that they calm without producing sleep and that their site of action in the central nervous system is predominantly subcortical. The principal sites of action are important regulating centers of the brain: thalamus, hypothalamus, reticular activating system and portions of the limbic system. Phenothiazine derivatives, besides being the most effective tranquilizers for treating severe emotional disorders, are also clinically useful for potentiating other analgesic or anesthetic drugs and for controlling vomiting. This rapidly growing group of drugs is of major importance in present-day psychopharmacologic therapy. Newer derivatives, especially of the piperazine type, appear to be highly effective as tranquilizers in low doses. They also produce fewer major complications from treatment. Rauwolfia alkaloids have decreased in importance in psychiatric use, but are still the basic drugs for treating hypertension. The substituted propanediols or butanediols are generally used as mild sedatives for less serious emotional disorders. The diphenylmethane derivatives, while chemically related, have a variety of pharmacologic actions which include sedation, stimulation, antihistaminic and anticholinergic effects. The ultimate role of these agents in the treatment of major emotional disorders, such as schizophrenic reactions, still is uncertain. However, the impetus these drugs have given to improved treatment of psychotic patients in mental hospitals has unquestionably been beneficial. The intensive attempts to determine their modes of action will very likely yield important advances in the understanding of possible neurophysiologic bases for mental illness.