Due to political strife and civil turmoil in Haiti during the production, the local government informed the film crew that they could not guarantee their safety for the remainder of the shoot. The crew subsequently relocated to nearby Dominican Republic to complete filming.
Newly wed, Bill Pullman's wife was invited to be an extra and appears on screen as the blonde who pushes a long needle through a willing man's cheek.
The actual investigations and findings of Wade Davis, upon which the character Dennis Alan is based, didn't amount to much. Davis's research was mostly dismissed by his peers, while the drug tetrodotoxin (which the film states has been under extensive study and was a mystery to science) was actually already well known in 1985 and today is used as an anesthetic.
The character of Christophe Durand was based on a man name Clairvius Narcisse who was stated to have died in 1962 and later risen as a zombie by a local Haitian witch doctor. Narcisse was found to have been poisoned by a paste drug called Datura, which caused memory loss, and forced to work as a slave on a sugar plantation. He escaped sixteen years later after his captors had all themselves died, and had also apparently been weaned off the Datura drug by eating salty foods, containing bromide, which counteracted the poison.
Author Wade Davis agreed to sell the book rights on the condition that Peter Weir direct and Mel Gibson star. Neither man had any involvement in the project.
Wes Craven: [the main character experiences traumatizing nightmares that reflect reality or affect reality] In this film, Dr. Dennis Alan experiences horrifying nightmares about being buried alive. Other Craven films such as A Nightmare on Elm Street (1984), Vampire in Brooklyn (1995), and Cursed (2005), respectively, also explore the theme of nightmares being linked to reality through trauma.