Green’s Dictionary of Slang

hook n.2

[hook v.1 (2f)]

(drugs) an addiction.

[US]P. Thomas Savior 7: I mean this was his first hook and...he made it to...the ‘kick factory’ [HDAS].

In phrases

off the hook

(US drugs) ceasing to take narcotic drugs.

[US](con. 1930s–60s) H. Huncke Guilty of Everything (1998) 236: That [the death of a dealer] took me off the hook pretty fast.
on the hook

(drugs) addicted to a drug.

[US](con. 1948) G. Mandel Flee the Angry Strangers 244: Dinch, you get kids on the hook for Buster?
[UK]‘Raymond Thorp’ Viper 124: I spotted some cats who might have been on the hook [...] human wrecks with blank stares.
[US]W. Brown Teen-Age Mafia 128: For the first week the stuff was free. By then he was on the hook.