[Ketamine-induced psychopathological changes in normal volunteers during conditions used for experimental psychoses...

The psychotomimetic properties of ketamine were studied in 9 physically and psychically normal medical students and nurses during 20 single-blind experiments. During the experiments any disturbance to the subject was avoided. A dose of 0.25 mg/kg produced psychical changes in every case, and 1 mg/kg caused an experimental psychosis every time. The latter starts in an "ideal" case with an expressive disturbance of consciousness down to the level of surgical anesthesia. 5-7 minutes after the start of the experiments the scalar change of consciousness lessens enabling the qualitative changes to become obvious. Strong short-time memory disturbance however prevents the subjects from describing coherently the large number of hallucinations and illusions which are frequently experienced. For several moments at the end of the experiment a strong disturbance of body-feeling combined with ataxia may still be present when consciousness is almost normal. - According to the observed psychopathological changes ketamine may be classified as a not LSD-typical hallucinogen. - It should be possible to lower the frequency of adverse reactions to ketaminemonanesthesia by preparing the patients for the strange experiences possible during emergence.