Altered States is a 1980 movie directed by British filmmaker Ken Russell. It deals with an American scientist, Eddie Jessup (played by William Hurt and based on John C. Lilly), who does experiments on human consciousness using hallucinogenic drugs, an isolation chamber, and himself as a guinea pig.
The movie is based on a novel of the same title by noted playwright Paddy Chayefsky, who also did the script adaptation. While the movie is decent enough for early-80s science fiction fare and has some very cool visuals, the novel is much better, and I highly recommend it.
The movie would have been much better if not for Russell's bias against Chayefsky. The problem was, Russell hated Chayefsky's script from the outset; he inexplicably felt he was "lowering himself" to work with the material. However, Chayefsky's contract stated that Russell could not rewrite or otherwise tamper with the script. So, Russell instructed his actors to speak their lines as quickly as they possibly could.
As a result, the poetic cadences in Chayefsky's dialog were destroyed, and some fairly high-level scientific discussion was rushed through, much to the detriment of audiences being able to understand and process what was said.
Enraged by Russell's sabotaging of his script, Chayefsky had his name removed from the film, adopting instead the pseudonym Sidney Aaron (his given first and middle names).
Despite all this, the film did very well and is the most financially successful of Russell's career to date.
The movie is also of note because it was the first film appearance of both William Hurt and Blair Brown. One also gets to see a very young Drew Barrymore before she rocketed to stardom in E.T.: The Extraterrestrial.