IBZM SPECT imaging of striatal dopamine-2 receptors in psychotic patients treated with the novel antipsychotic substance quetiapine in comparison to clozapine and haloperidol.
We investigated the striatal dopamine-2 (D2) receptor occupancy caused by different antipsychotic substances in 18 psychotic patients (16 with schizophrenic and two with schizoaffective disorder according to DSM-IV) with single photon emission computed tomography (SPECT) using 123I-iodobenzamide (IBZM) as tracer substance. Four patients were treated with the novel antipsychotic compound quetiapine (300-700 mg/day), six with clozapine (300-600 mg/ day) and eight with haloperidol (10-20 mg/day). They were compared with eight healthy controls. Measurement of S/F ratios and consecutive calculation of D2 receptor occupancy revealed a significantly lower striatal D2 occupancy rate with quetiapine and clozapine in comparison to haloperidol. In correspondence with the low striatal D2 receptor occupancy rates and again in contrast to the haloperidol treatment group, there were no extrapyramidal motor side-effects (EPS) in the quetiapine and clozapine treatment groups. Therefore, the reported data support the position that quetiapine can be considered to be an atypical antipsychotic substance due to its relatively weak striatal D2 receptor blocking property and therefore its low propensity to induce EPS.
Küfferle
B
B
Department of General Psychiatry, University Hospital for Psychiatry, Vienna, Austria.
Tauscher
J
J
Asenbaum
S
S
Vesely
C
C
Podreka
I
I
Brücke
T
T
Kasper
S
S
D000328:Adult; D014150:Antipsychotic Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use; D001549:Benzamides; D003024:Clozapine / Q000493:pharmacokinetics / Q000627:therapeutic use; D003987:Dibenzothiazepines / Q000493:pharmacokinetics* / Q000627:therapeutic use; D018492:Dopamine Antagonists / Q000493:pharmacokinetics / Q000627:therapeutic use; D005260:Female; D006220:Haloperidol / Q000493:pharmacokinetics / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D017072:Neostriatum / Q000033:anatomy & histology / Q000378:metabolism*; D011618:Psychotic Disorders / Q000188:drug therapy / Q000378:metabolism; D011759:Pyrrolidines; D000069348:Quetiapine Fumarate; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D012559:Schizophrenia / Q000188:drug therapy / Q000378:metabolism*; D015899:Tomography, Emission-Computed, Single-Photon
D014150:Antipsychotic Agents; D001549:Benzamides; D003987:Dibenzothiazepines; D018492:Dopamine Antagonists; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; D000069348:Quetiapine Fumarate; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide; D003024:Clozapine; D006220:Haloperidol