Heroin or diacetylmorphine, C21H23NO5
It was invented in 1895 by Heinrich Dreser, working for the Bayer Company of Elberfeld, Germany, developed as a drug without the common morphine side effects. Bayer promptly began production of diacetylmorphine under the trademark "heroin" and selled it as caugh medicine.
Methadone is another drug often used to substitute for heroin in treatment for heroin addiction.
See also Recreational drug use