scopolamine skōpŏl´əmēn, –mĭn [key] or hyoscinehī´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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