Although phencyclidine (PCP) and drugs of similar chemical structure (arylcyclohexylamines) are often called HALLUCINOGENS, they rarely produce HALLUCINATIONS, and the sensory distortions or apparent hallucinations that are produced are not the same type as LSD-induced hallucinations. Instead, phencycli-dine belongs to a unique class of drugs called the dissociative anesthetics. Phencyclidine was developed in the 1950s as an anesthetic for veterinary medicine and later was tested in human surgical patients. There was great potential for PCP as an anesthetic because it produced minimal effects on the heart and breathing was not suppressed. Unfortunately, the adverse side effects of PCP (e.g., dysphoria [unhappy, ill] and psychotic symptoms) led to a termination of the human clinical trials. The drug is no longer manufactured for veterinary use because supplies were diverted (stolen) and the drug became widely abused in the 1970s. Keta-mine, a drug chemically similar to PCP, is...