Requiem for a Dream is a great movie, but very dark and depressing. It's been a while since I have seen it because there needs to be quite a long stretch of time between each viewing, thanks again for the votes!
These are some movies from the drug genre that I thought would make a good list, to narrow it down, I've only listed movies where drugs are part of the main storyline as opposed to when they are just on the sidelines.
there is a brazilian movie that could be in, called "Arido Movie".
Nice list.
Where's Cheech & Chong?