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In vivo (123)I IBZM SPECT imaging of striatal dopamine 2 receptor occupancy in schizophrenic patients
C Barnas1, S Quiner, J Tauscher
1Department of General Psychiatry, University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria.
Rationale:
Single photon emission computed tomography (SPECT) using (123)I iodobenzamide (IBZM) as tracer substance has been shown to be a useful tool to visualize dopamine 2 (D2) receptor occupancy.
Objectives:
We investigated the striatal D2 receptor occupancy of zotepine which is referred to the class of atypical antipsychotic drugs.
Methods:
(123)I IBZM and SPECT were used to visualize striatal dopamine 2 (D2) receptor occupancy in zotepine-treated schizophrenic patients. Two groups of schizophrenic patients receiving either 150 mg/day zotepine (n=6) or 300 mg/day (n=6) underwent examination. For the quantification of striatal D2 receptor occupancy, striatal IBZM binding in patients treated with antipsychotics was compared to untreated healthy controls (n=8) reported earlier.
Results:
Zotepine led to a mean overall striatal D2 receptor occupancy of 73%. Patients with 150 mg daily showed a significantly lower occupancy (65.8%, SD=6.2) than patients with 300 mg/day (77.8%, SD=10.7; P<0.05). No clinically relevant extrapyramidal side effects occurred during treatment with zotepine.
Conclusions:
There was no correlation between the degree of striatal D2 receptor occupancy and clinical improvement.