on the junk
slang Currently using, intoxicated by, or addicted to narcotics, especially heroin. I assumed he was on the junk because the glassy, vacant look in his eyes. You can tell Tara's back on the junk again—she's been looking really sick and out of it lately.
on the junk
mod. on drugs; addicted to drugs. (see also junk.) Max has been on the junk for all of his adult life.