Green’s Dictionary of Slang

dusted adj.2

[SE dust, to clean up]

1. (drugs) having consumed and finished off a drug.

[US]J.E. Schmidt Narcotics Lingo and Lore.
[US]Hardy & Cull Drug Lang. and Lore.

2. (US campus) drunk.

[US]Current Sl. I:1 2/1: Dusted To be drunk.