Jason Patric actually did shoot up for authenticity's sake for the film though the substances he used in his syringes were either saline or vitamins.
As composer of the music score, Eric Clapton was initially reluctant to include "Tears in Heaven" in the film. Mourning the death of his son Conor, about the loss of whom the song had been written, Clapton wasn't sure if it should be made public. Director Lili Fini Zanuck managed to change his mind by convincing him that the song might help someone dealing with grief in their own life.
Tom Cruise turned down the part later played by Jason Patric, as he didn't like the idea of scenes involving him taking drugs.
Jason Patric appeared as an undercover Narcotics officer in the movie Narc (2002), which appeared to be a familiar resemblance to his character in this movie, with the difference of a "post drug addiction officer". Tom cruise financed the project that also starred Ray Liotta.
The main character of the computer game StarCraft was named after the main protagonist of this movie, Jim Raynor.