In his 'Ziggy' period Bowie used heroin, in that period he got friendly with
Iggy , who was a well known heroin addict
Bowie also hanged around Warholds community around his 'Ziggy' period,
and I definately know that's it's well know fact that Bowie used heroin
with Lou Reed [and the people around Lou]
Later he went on with cocaine.
His former wife Angie wrote a book where she mentioned Bowie's cocaine
addiction.
IMHO was the model [now his wife] Noami Cambell also a cocaine user,
at the time they became friendly
[btw, now I think of it, is Naomi still married to Bowie?]
and I didn't even start with Freddy Mercury and Elton John [one is really
dead, the other brain dead
] sorry, just joking