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Lookup NU author(s): Emeritus Professor Elaine Perry, Dr Louise MacDougall
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BACKGROUND: In healthy individuals, ketamine hydrochloride and amphetamine sulfate produce cognitive, behavioral, and subjective effects resembling endogenous psychoses. Studying the comparative and interactive effects of these agents may provide insights into the roles of the glutamate and monoamine systems in psychosis and cognition. OBJECTIVES: To directly compare the effects of ketamine and amphetamine and to explore their interactive effects within individuals. DESIGN: Placebo-controlled, randomized, double-blind psychopharmacologic trial. SETTING AND PARTICIPANTS: Forty-one healthy individuals recruited from the community who completed up to 4 test days. MAIN OUTCOME MEASURES: On each test day, participants received amphetamine (a 1-minute infusion of amphetamine sulfate, 0.25 mg/kg, or saline) and ketamine (a 1-minute intravenous infusion of ketamine, 0.23 mg/kg, followed by a 1-hour infusion of 0.5 mg/kg or an identical saline bolus and infusion). The order of amphetamine and ketamine infusions was randomized. RESULTS: At the doses studied, ketamine and amphetamine produced positive symptoms and euphoria. However, perceptual changes were produced only by ketamine, and hostility, grandiosity, and somatic concern were stimulated only by amphetamine. Amphetamine and ketamine produced conceptual disorganization, but only ketamine produced concrete ideation and unusual mannerisms. Ketamine produced negative symptoms and disrupted delayed recall. Ketamine and amphetamine showed 3 types of interactive effects: (1) amphetamine attenuated the impairment of working memory produced by ketamine; (2) amphetamine and ketamine had additive effects on thought disorder, arousal, and euphoria; and (3) amphetamine and ketamine had less-than-additive effects on psychosis. CONCLUSIONS: These findings implicate N-methyl-D-aspartate glutamate receptors and dopamine systems in psychosis. However, glutamate and dopamine may differentially contribute to psychosis, thought disorder, and euphoria. Regarding medication development for cognitive dysfunction, the pattern of the interactive effects of ketamine and amphetamine is consistent with the hypothesis that facilitation of prefrontal cortical dopamine levels would attenuate some cognitive impairments associated with deficits in N-methyl-D-aspartate receptor function.
Author(s): Krystal JH, Perry E, Gueorguieva R, Belger A, Madonick SH, Abi-Dargham A, Cooper TB, Macdougall L, Abi-Saab W, D'Souza DC
Publication type: Article
Publication status: Published
Journal: Archives of General Psychiatry
Year: 2005
Volume: 62
Issue: 9
Pages: 985-994
ISSN (print): 0003-990X
ISSN (electronic): 1538-3636
Publisher: American Medical Association
URL: http://dx.doi.org/10.1001/archpsyc.62.9.985
DOI: 10.1001/archpsyc.62.9.985
Notes: 0003-990x Clinical Trial Journal Article Randomized Controlled Trial
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