Antipsychotic drugs improve psychosis in patients within 24 hours of treatment: Study

For immediate release: May 26, 2005 (Toronto) For the first time, scientists at the Centre for Addiction and Mental Health (CAMH) and the University of Toronto have published research showing that antipsychotic drugs begin to improve psychosis in patients within the first 24 hours of treatment.  This result is contrary to the prevailing assumption that it took two weeks for the drugs to have any effect on symptoms. Published in the May 2005 issue of the American Journal of Psychiatry, this discovery came as a result of analyzing brain scans from positron emission tomography data, and can direct future clinical research and theories on the antipsychotic effects of drugs.
 
"Our discovery could lead to improvements in the way antipsychotic drugs are prescribed to patients, and also help in simplifying the development of new improved antipsychotic medications," said Dr. Shitij Kapur, Vice President of Research at CAMH and the senior author of the study. "We were surprised to find that antipsychotic action in the brain may be more closely related to the blockade of dopamine transmission than originally thought. This suggests that simple dopamine receptor blockade can explain how antipsychotic drugs work, an area that has always been under debate."

In this study, 311 patients with a diagnosis of schizophrenia disorder were randomly assigned to receive a placebo or an antipsychotic medication such as olanzapine or haloperidol. Patients were monitored for changes in their behaviour once the drugs were administered, after 2 hours and then at 24 hours using structured rating scales called 'Positive and Negative Syndrome Scale' and 'Clinical Global Impressions'.

Analysis showed that a change in the patient's psychosis (which included conceptual disorganization, hallucinatory behavior, unusual thought content) was evident within the first 24 hours for both drugs.

"In addition to its implications for understanding the mechanism of action of antipsychotic medications, this study has important clinical implications. It suggests that physicians should be able to know within days, not weeks, whether these medications are working, and make changes to the dose or to the choice of medications on a much more rapid timeframe that is currently done," according to study co-author Dr. Robert Zipursky, Clinical Director of the Schizophrenia Program at CAMH and Tapscott Chair in Schizophrenia Studies at the University of Toronto.

The first drugs to be useful in treating the hallucinations and delusions of many patients with the psychotic disorder schizophrenia were discovered nearly 50 years ago. Since then, they have been conventionally accepted to help with psychosis, but that they had a "delayed onset" of 2-3 weeks or more.  Contrary to this prevailing assumption, this new finding that drugs have a more immediate effect suggest that simple dopamine receptor blockade can explain how antipsychotic drugs work, a finding that can direct future theories and clinical research on antipsychotic medication.

CAMH is a Pan American Health Organization and World Health Organization Collaborating Centre and a teaching hospital fully affiliated with the University of Toronto.

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For more information or a copy of the study, please contact: Sylvia Hagopian, CAMH Media Relations Coordinator at (416) 595-6015.

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