scopolamine skōpŏl´əmēn, –mĭn [key] or hyoscine hī´əsēn˝, –sĭn [key], alkaloid drug obtained from plants of the nightshade family (Solanaceae), chiefly from henbane , Hyoscyamus niger. Structurally similar to the nerve substance acetylcholine , scopolamine acts by interfering with the transmission of nerve impulses by acetylcholine in the parasympathetic nervous system and produces symptoms typical of parasympathetic system depression: dilated pupils, rapid heartbeat, and dry skin, mouth, and respiratory passages. Because scopolamine depresses the central nervous system, it is used as a sedative prior to anesthesia and as an antispasmodic in certain disorders characterized by restlessness and agitation, e.g., delirium tremens, psychosis, mania, and Parkinsonism. When combined with morphine , the effect produced is a tranquilized state known as twilight sleep; this combination of drugs was formerly used in obstetrics but is now considered too dangerous. Overdosage of scopolamine causes delirium, delusions, paralysis, and stupor. The alkaloid is found in a variety of nonprescription sedatives.
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