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Heterocyclic compound, a naturally occurring alkaloid found in opium, used in medicine as a cough suppressant and analgesic drug. It exerts its effects by acting on the central nervous system (brain and spinal cord). Chemically it is methylmorphine, the methyl ether of morphine, an alkaloid of the phenanthrene type; its action is weaker than that of morphine, and it is less likely to lead to drug addiction.
This entry comes from Encyclopædia Britannica Concise. For the full entry on codeine, visit Britannica.com.