RT Journal Article SR Electronic T1 D2 Receptor Occupancy During High- and Low-Dose Therapy with the Atypical Antipsychotic Amisulpride: A 123I-Iodobenzamide SPECT Study JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1028 OP 1033 VO 46 IS 6 A1 Christian la Fougère A1 Eva Meisenzahl A1 Gisela Schmitt A1 Jan Stauss A1 Thomas Frodl A1 Klaus Tatsch A1 Klaus Hahn A1 Hans-Jürgen Möller A1 Stefan Dresel YR 2005 UL http://jnm.snmjournals.org/content/46/6/1028.abstract AB Amisulpride appears to be an effective agent for treating positive or negative symptoms of schizophrenia, depending on dose. The aim of this study was to assess striatal dopamine D2 receptor availability by means of 123I-iodobenzamide (IBZM) SPECT in patients treated with high and low doses of this atypical antipsychotic drug. Methods: Twenty-nine patients (19 men and 10 women, age range, 19–68 y) with schizophrenia treated with high doses (15 patients; 400–1,200 mg/d; mean dose, 666.7 ± 219.3 mg/d) or low doses (14 patients; 50–300 mg/d; mean dose, 228.6 ± 93.5 mg/d) of amisulpride were examined. For assessment of plasma amisulpride concentration, blood samples were taken. Brain SPECT was performed 2 h after intravenous injection of 185 MBq of 123I-IBZM. For semiquantitative evaluation, transverse slices corrected for attenuation (Chang’s first-order method) were used to calculate specific binding in the striatum, with the frontal cortex used as background. Results: In all patients treated with amisulpride, specific binding of 123I-IBZM to D2 receptors was significantly lower (P < 0.001) than in healthy controls (0.95). Both groups treated with amisulpride differed significantly in specific binding of 123I-IBZM to dopamine D2 receptors (0.20 vs. 0.31, P < 0.05). D2 receptor blockade correlated well with the administered dose of amisulpride and with amisulpride plasma concentration. Conclusion: Our findings suggest that amisulpride treatment leads to a significant occupancy of postsynaptic dopamine D2 receptors. The blockade of D2 receptors tends to be significantly lower in patients receiving low-dose amisulpride therapy than in patients receiving high-dose therapy.