Dopefiend

[Britney]

Someone addicted to hard drugs (crack, heroin, etc) that fiends for them so badly that they will do irrational and disproportion things to obtain said drugs.

[PussyCat]

noun, adj. Desperate and shameless behavior of a drug addicted person. It causes them to lose all values and self-respect and drives them towards their main priority and that is to get high.

[Jason Yan]

Someone who is addicted to drugs or narcotics so much that they are willing to steal or kill for it.