Takashi Tsuboi1, Takefumi Suzuki2, Robert R Bies3, Gary Remington4, Bruce G Pollock5, Masaru Mimura1, Hiroyuki Uchida6. 1. Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan. 2. Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan; Department of Psychiatry, Inokashira Hospital, Tokyo, Japan. 3. Division of Clinical Pharmacology, Indiana University School of Medicine, Indianapolis, IN, USA; Indiana Clinical and Translational Sciences Institute, Indianapolis, IN, USA; Geriatric Psychiatry Division, Centre for Addiction and Mental Health, Toronto, ON, Canada. 4. Department of Psychiatry, University of Toronto, Toronto, ON, Canada; Schizophrenia Division, Centre for Addiction and Mental Health, Toronto, ON, Canada. 5. Geriatric Psychiatry Division, Centre for Addiction and Mental Health, Toronto, ON, Canada; Department of Psychiatry, University of Toronto, Toronto, ON, Canada. 6. Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan; Geriatric Psychiatry Division, Centre for Addiction and Mental Health, Toronto, ON, Canada. Electronic address: hiroyuki.uchida.hu@gmail.com.
Abstract
OBJECTIVE: Blockade of dopamine D₂ receptors with antipsychotics above 65% is associated with optimal chance of clinical response although recent data suggest a lower threshold for the maintenance treatment of schizophrenia. The objective of this study was to prospectively examine whether such continuous high blockade would be necessary for maintenance treatment. METHOD: In this single-blind, 52-week, randomized controlled trial, clinically stable patients with schizophrenia receivingrisperidone or olanzapine were randomly assigned to the continuous D₂ blockade (i.e. an estimated trough D2 blockade of >65%) or non-continuous blockade group (i.e. an estimated peak level of >65% with an estimated trough level of <65%). Oral doses corresponding to the assigned blockade levels were estimated from random plasma drug concentrations, using the models we developed; antipsychotic doses were then adjusted accordingly. Psychopathology and side effects were assessed at baseline and one year with the Positive and Negative Syndrome Scale (PANSS), Simpson-Angus Scale (SAS), and Abnormal Involuntary Movement Scale (AIMS). RESULTS:Sixty-eight subjects (34 in each group) were enrolled. Twenty-six (76.5%) and thirty-one (91.2%) subjects completed the study in the continuous and non-continuous blockade groups, respectively, without any significant group difference. No significant differences were found on any of the assessment scales between the two groups. The degree of dosage change was small in both groups. CONCLUSION: These results offer support that the threshold for D₂ receptor blockade in the maintenance treatment can be lower than 65%. However, these preliminary findings have to be confirmed through double-blind, larger scale trials with longer follow-up periods.
RCT Entities:
OBJECTIVE: Blockade of dopamine D₂ receptors with antipsychotics above 65% is associated with optimal chance of clinical response although recent data suggest a lower threshold for the maintenance treatment of schizophrenia. The objective of this study was to prospectively examine whether such continuous high blockade would be necessary for maintenance treatment. METHOD: In this single-blind, 52-week, randomized controlled trial, clinically stable patients with schizophrenia receiving risperidone or olanzapine were randomly assigned to the continuous D₂ blockade (i.e. an estimated trough D2 blockade of >65%) or non-continuous blockade group (i.e. an estimated peak level of >65% with an estimated trough level of <65%). Oral doses corresponding to the assigned blockade levels were estimated from random plasma drug concentrations, using the models we developed; antipsychotic doses were then adjusted accordingly. Psychopathology and side effects were assessed at baseline and one year with the Positive and Negative Syndrome Scale (PANSS), Simpson-Angus Scale (SAS), and Abnormal Involuntary Movement Scale (AIMS). RESULTS: Sixty-eight subjects (34 in each group) were enrolled. Twenty-six (76.5%) and thirty-one (91.2%) subjects completed the study in the continuous and non-continuous blockade groups, respectively, without any significant group difference. No significant differences were found on any of the assessment scales between the two groups. The degree of dosage change was small in both groups. CONCLUSION: These results offer support that the threshold for D₂ receptor blockade in the maintenance treatment can be lower than 65%. However, these preliminary findings have to be confirmed through double-blind, larger scale trials with longer follow-up periods.