Striatal D2/D3 receptor occupancy, clinical response and side effects with amisulpride: an iodine-123-iodobenzamide SPET study.

INTRODUCTION: Amisulpride appears to be an effective atypical agent for treating schizophrenia in a dose-dependent manner. METHODS: 29 patients suffering from schizophrenia or schizoaffective disorder were treated with a broad dose range of amisulpride (50-1 200 mg/day, mean: 455.2+/-278.8 mg/day). After 2 weeks, brain single photon emission tomography (SPET) scans were performed two hours after intravenous injection of 185 MBq [123I]IBZM. Clinical evaluations and ratings of extrapyramidal symptoms were performed at baseline and after steady state treatment of two weeks with amisulpride. RESULTS: In patients treated with amisulpride, specific binding of [123I]IBZM to D2 receptors was significantly decreased (p<0.001) compared to healthy controls. D2 receptor blockade correlated well with administered doses and plasma concentrations of amisulpride. Extrapyramidal side effects, which had to be treated with biperiden, were observed in 31% of the patients. Clinical response was very good, without correlation between the response and striatal D2 occupancy. DISCUSSION: Within the first two weeks of treatment with the atypical antipsychotic amisulpride a significant occupancy of striatal postsynaptic dopamine D2 receptors was achieved. At the same time amisulpride shows an excellent tolerability with good efficacy.