Is "character takes drugs and hallucinates vital aspects of his backstory" a workable exposition tool, or is it just stupid?

So the prologue to my what-might-generously-be-called-a-novel is essentially a character just taking some Fantastic Drug and getting some good ol' Maybe Magic, Maybe Mundane hallucinations of his dead sister and a series of vignettes explaining his life story, which rather conveniently showcases most major events in this world's recent history. It's basically an expodump just with slightly more showing instead of telling.

I'm just kinda worried that this might be a bit confusing to get all of this information out in the very first chapter, especially since the drug isn't really a major plot point (a few characters use it and it's a major source of income for the villains but it doesn't really feature directly into the narrative) and the POV is from a Teaser-Only Character who suffers from a self-inflicted Plot-Triggering Death, so his personal story isn't that important in the scheme of things. I just wanted to easily establish the backstory by showing things in a way that at least has some kind of human element to it as well as potentially developing a minor character.

Any thoughts? Does it sound workable?

Workable, yes, but I'm afraid chances are that it is going to feel confusing and stupid to your readers. Giving them something that kind of didn't really happen, to a character who doesn't even matter, using something that's a plot element but at that point unknown ... well ... it may be something useful for an interlude, but for the prologue personally I don't think so.

Believe it or not, this exact thing happened in an episode of This Is Us, which is otherwise a realistic (but very dramatic) show.

I agree with : this would be a hard sell in the first chapter. It's a technique better utilized after we know more about the character. The instance in This Is Us happened midway through the first season, for comparison.