Meaning of "chasing the dragon"

a highly addictive analgesic drug derived from morphine, often used illicitly as a narcotic producing euphoria.

her·o·in

hĕr′ō-ĭn
her·o·in  (hĕr′ō-ĭn)
n.
A white, odorless, bitter crystalline compound, C21H23NO5, that is derived from morphine and is a highly addictive illegal narcotic. Also called diacetylmorphine.

[German, originally a trademark.]

heroin

ˈhɛrəʊɪn
heroin (ˈhɛrəʊɪn)
n
1. (Pharmacology) a white odourless bitter-tasting crystalline powder related to morphine: a highly addictive narcotic. Formula: C21H23NO5. Technical names: diamorphine or diacetylmorphine
2. (Recreational Drugs) a white odourless bitter-tasting crystalline powder related to morphine: a highly addictive narcotic. Formula: C21H23NO5. Technical names: diamorphine or diacetylmorphine
[C19: coined in German as a trademark, probably from hero, referring to its aggrandizing effect on the personality]

her•o•in

(ˈhɛr oʊ ɪn)
her•o•in (ˈhɛr oʊ ɪn) n.
a white crystalline powder, C21H23NO5, derived from morphine, that is narcotic and addictive: manufacture or import is prohibited in the U.S. and other nations.
[1895–1900; formerly trademark; < German Heroin < Greek hērō-, s. of hḗrōs hero + German -in -in1; allegedly so called from feelings of power and euphoria that it induces]