Are you thinking of a book where a kid has to deal with drug use by adults in their life, or by a peer, or is the protagonist themselves a user? How detailed or graphic are the scenes involving drug use? How central is drug use to the story? Do you show the mechanics of shooting up or smoking, or do you describe someone under the influence, or focus on the emotional effects. I'm guessing detailed or graphic treatments of drug addiction wouldn't be an easy sell for that age group, but a book where a child is dealing with someone else's--a parent's or older sibling's maybe--addiction issues might be.
As far as drug use by the pre-teen character or their peers, I'm guessing it might depend on how central the drug use is to the plot and character and on how it's shown. Judy Blume showed some 7th grade boys experimenting with alcohol and getting sick drunk in
Then Again Maybe I Won't back in the 70s also, but that wasn't the focus of the novel. Jr. high age protagonists are supposed to be a harder sell today, though I imagine 10-12-year-olds probably "read up" about middle-school kids, just as we did when I was a kid.
A Hero Ain't Nothin But a Sandwich by Alice Childress featured a 13-year-old protagonist who becomes addicted to heroin. It was published in 1973, and is very dated in some ways, so it may have been before the modern marketing categories of "mid grade" and YA existed as they do now. It sort of straddled the line between modern YA and MG. I think it was also pitched at older teens (it was involved in a
court case where certain books were pulled from high school shelves), but teens tend to read up, so I am guessing younger kids probably read it too. I don't remember how old I was when I ran across it myself--middle school, maybe, and I found it in a library.