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J Res Pharm Pract. 2013 Oct;2(4):138-44. doi: 10.4103/2279-042X.128142.

Onset of action of atypical and typical antipsychotics in the treatment of acute psychosis.

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Department of Psychiatry, Behavioral Sciences Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
Department of Psychiatry, Psychosomatic Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
Department of Psychiatry, Azad University of Najaf Abad, Isfahan, Iran.
Department of Biostatistics, Isfahan University of Medical Sciences, Isfahan, Iran.



Antipsychotic medications are the frontline treatment for the most psychotic disorders. The aim of this study is to compare the onset of action of the first and second generation antipsychotics and the rate of their side-effects in the treatment of acute psychosis.


In a double-blind, controlled clinical trial, 40 acute psychotic patients were randomly allocated in four groups and treated with each of the four antipsychotics: olanzapine, risperidone, haloperidol or thiothixene. The onset of action of each drug was assessed by the Positive and Negative Symptoms Scale. The data were analyzed by Wilcoxon (Gehan) survival and Log Rank analysis, using SPSS version 20.0.


Initial response was observed in 97.5% (N = 39) of subjects during 2 weeks of intervention. The mean time to the first response was 6.15 ± 2.9 days and this was significantly shorter for risperidone than others. The most common side-effects were sedation and drug induced Parkinsonism.


Risperidone represented shorter onset of action for the treatment of acute psychotic symptoms compared with olanzapine, haloperidol and thiothixene.


Acute psychosis; antipsychotic; onset of action; response; side effect

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