[I-123] IBZM SPECT FOR IMAGING OF STRIATAL D-2 DOPAMINE-RECEPTORS IN 56 SCHIZOPHRENIC-PATIENTS TAKING VARIOUS NEUROLEPTICS

Objective: The purpose of this study was to compare the binding of var ious typical and atypical neuroleptics to striatal D-2 dopamine recept ors in schizophrenic patients. Method: Fifty-six inpatients with schiz ophrenia, including 14 with schizoaffective disorder and one with schi zophreniform disorder, were evaluated. Fourteen patients were neurolep tic free. Single photon emission computed tomography (SPECT) was perfo rmed 90 minutes after intravenous injection of [I-123]benzamide ([I-12 3]IBZM). Subsequent semiquantitative analysis of D-2 receptor binding was done with the use of the basal ganglia (striatum)/frontal cortex ( BG/FC) ratio of activity. Clinical symptoms were rated with the Positi ve and Negative Syndrome Scale and the Hamilton Depression Rating Scal e. Results: The BG/FC ratios in patients taking typical neuroleptics w ere significantly lower than those in the neuroleptic-free subjects bu t not lower than those in the patients taking atypical neuroleptics (c lozapine, remoxipride). For atypical antipsychotics, a dose-dependent relationship with striatal D-2 receptor binding could not be demonstra ted. BG/FC ratios were not significantly correlated with clinical symp toms or with duration of illness. Conclusions: The results indicate th at [I-123]IBZM SPECT is useful for semiquantitative imaging of striata l D-2 dopamine receptors and for estimating their blockade by neurolep tics. Thus, it may improve drug monitoring in psychiatric patients. Fu rthermore, the findings suggest a complex relationship between the ant ipsychotic effect of atypical neuroleptics and D-2 receptor blockade.