[123I]IBZM SPECT for imaging of striatal D2 dopamine receptors in 56 schizophrenic patients taking various neuroleptics.
OBJECTIVE
The purpose of this study was to compare the binding of various typical and atypical neuroleptics to striatal D2 dopamine receptors in schizophrenic patients.


METHODS
Fifty-six inpatients with schizophrenia, including 14 with schizoaffective disorder and one with schizophreniform disorder, were evaluated. Fourteen patients were neuroleptic free. Single photon emission computed tomography (SPECT) was performed 90 minutes after intravenous injection of [123I]benzamide ([123I]IBZM). Subsequent semiquantitative analysis of D2 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 Positive and Negative Syndrome Scale and the Hamilton Depression Rating Scale.


RESULTS
The BG/FC ratios in patients taking typical neuroleptics were significantly lower than those in the neuroleptic-free subjects but not lower than those in the patients taking atypical neuroleptics (clozapine, remoxipride). For atypical antipsychotics, a dose-dependent relationship with striatal D2 receptor binding could not be demonstrated. BG/FC ratios were not significantly correlated with clinical symptoms or with duration of illness.


CONCLUSIONS
The results indicate that [123I]IBZM SPECT is useful for semiquantitative imaging of striatal D2 dopamine receptors and for estimating their blockade by neuroleptics. Thus, it may improve drug monitoring in psychiatric patients. Furthermore, the findings suggest a complex relationship between the antipsychotic effect of atypical neuroleptics and D2 receptor blockade.
Klemm
E
E
Department of Nuclear Medicine, University of Bonn, Germany.
Grünwald
F
F
Kasper
S
S
Menzel
C
C
Broich
K
K
Danos
P
P
Reichmann
K
K
Krappel
C
C
Rieker
O
O
Briele
B
B
Hotze
A L
AL
Möller
H J
HJ
Biersack
H J
HJ
D000328:Adult; D014150:Antipsychotic Agents / Q000378:metabolism* / Q000494:pharmacology / Q000627:therapeutic use; D001549:Benzamides; D003287:Contrast Media; D003342:Corpus Striatum / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism*; D018492:Dopamine Antagonists; D004305:Dose-Response Relationship, Drug; D005260:Female; D005625:Frontal Lobe / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008297:Male; D011569:Psychiatric Status Rating Scales; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000378:metabolism*; D012559:Schizophrenia / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000378:metabolism*; D015899:Tomography, Emission-Computed, Single-Photon
D014150:Antipsychotic Agents; D001549:Benzamides; D003287:Contrast Media; D018492:Dopamine Antagonists; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide