D-2-DOPAMINE RECEPTOR OCCUPANCY MEASURED BY IBZM-SPECT IN RELATION TOEXTRAPYRAMIDAL SIDE-EFFECTS

The purpose of this study was to compare striatal D-2 dopamine recepto r occupancy of various typical neuroleptics and clozapine in relation to the occurrence of extrapyramidal side effects (EPS). Forty-four inp atients with schizophrenia, including 12 patients with schizodominant schizoaffective disorder, were evaluated using I-123-iodobenzamide (IB ZM) and single photon emission computed tomography. Striatal D-2 dopam ine receptor occupancy was estimated by use of a striatal/frontal cort ex ratio (ST/FC) of IBZM binding. Fourteen patients were neuroleptic-f ree and served as controls. Six patients were treated with clozapine a nd 24 patients were treated with various typical neuroleptics. ST/FC r atios in patients taking typical neuroleptics were significantly lower than those who were neuroleptic free or treated with clozapine. Patie nts with EPS had lower ST/FC ratios than those without EPS. A signific ant linear relationship between ST/FC ratios and severity of EPS estim ated by the Simpson-Angus-Scale was established (r=-0.51, p=0.041).