I have Altered States on DVD. A lot of the attention for the movie is on the psychedelic hallucination sequences, but I also really love the dialogue. I may be the only one.
It’s also part of a small sub-genre that so far consists of it, X the Man with X-ray Eyes, and The Mask. (The 3D one from 1960, not the one with Jim Carrey) They’re all sort of clearly doing an update of Frankenstein for the LSD age.
The dialogue from Altered States was written by Paddy Chayefsky. He apparently complained about the breakneck delivery, and the tendency of the actors to shout it at one another, but I kind of see why the actors and director went with that.