Scientists conducting the study said volunteers were carefully screened for mental illness and signed consent forms that warned of side effects such as hallucinations and mood changes. But some critics said the risks of the drug are not fully known and questioned the ethics of inducing psychotic behavior in healthy people. Often used as a prescription surgical anesthetic for people and animals, the Food and Drug Administration-approved drug can cause mild hallucinations, confusion and fear with regular use.
Severe hallucinations are possible with large doses.
The Boston Globe reported Thursday that healthy subjects run the risk of flashbacks months after using ketamine. Adil Shamoo, a University of Maryland bioethicist, told the newspaper. But scientists say ketamine can help unlock the mysteries of mental illness, especially schizophrenia and Alzheimer's disease, by giving researchers insight into the nature of hallucinations and mood disorders. The experiments began in the early 1990s and ended more than a year ago. They were designed to provoke symptoms of schizophrenia in healthy people during a one-time exposure, said Dr. Trey Sunderland, chairman of NIMH's review board.