D2 Receptor Occupancy During High- and Low- Dose Therapy with the Atypical Antipsychotic Amisulpride: A 123I-Iodobenzamide SPECT Study

Amisulpride appears to be an effective agent for treating posi-tive 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 concentra-tion, 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 at-tenuation (Chang’s first-order method) were used to calculat