HYOSCINE is the chief of the alkaloids (q.v.) of Datura metel, and is colourless syrup, soluble in most ordinary solvents, and yielding crystalline salts. (Its formula is Of these the hydrobromide, C17H2101N, is that generally used in medicine. It forms colourless rhombs, which melt at 193— 194°C. Hyoscine is optically active (see STEREOCHEMISTRY), the natural base being laevo-rotatory ([ al.= —18 ° to —28°). It is also known as scopolamine and atroscine.
Laevo-hyoscine is easily racemized to atroscine (compare atro pine) which can be crystallized and yields crystalline salts, usually melting 10-14°C below the corresponding salts of the natural laevo-base. Hyoscine is a mydriatic, like atropine, but is princi pally used as a sedative in acute mania, and with morphine to produce the so-called "twilight sleep" in maternity cases. Chem ically, hyoscine is closely related to atropine.