Green’s Dictionary of Slang

chang n.

(drugs) cocaine.

2008		J. Niven Kill Your Friends (2009) 7: This grape-brain [...] has been further buffoonerised by years of chronic chang abuse.
2018		Guardian 11 May 🌐 The mental image of Trump and Yeezy discussing their favourite Captain Beefheart tracks in the gents, as they tackle a 2nd line of finest Bolivian chang.

In derivatives

changed up (adj.)

intoxicated by cocaine.

2008

J. Niven Kill Your Friends (2009) 41: A load of drunk, chang’d-up fools shout abuse at each other.