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D2 dopamine receptor occupancy during treatment with flupentixol decanoate in comparison to risperidone, olanzapine, clozapine, haloperidol and haloperidol decanoate – A 123I-IBZM SPECT study: D2 receptor occupancy under flupentixol decanoate
The aim of the study was to evaluate the degree of D2 dopamine receptor occupancy in relation to the dosage of flupentixol decanoate.
By means of IBZM SPECT we investigated 17 patients meeting ICD-10 research criteria for Schizophrenia or schizoaffective disorder receiving flupentixol decanoate treatment with a fixed dosage for at least 2 months.
Compared to a sample of 9 drug naive schizophrenic patients with binding values ranging from 84,2% to 136,8%, D2 dopamine receptor binding of the ligand was reduced in all flupentixol decanoate treated patients with binding values ranging from 9,5% to 73,7%. The degree of neuroleptic – free receptors displayed an exponential dose-response relationship (R2=0.83, p<0.0001).
Compared to previous studies our data suggest that D2-dopamine receptor occupancy under 20mg / 2 weeks of flupentixol decanoate 1 week after injection corresponds approximately to an oral dose of 3.5mg / day risperidone, 10mg/day olanzapine, 5mg/day haloperidol, and 55mg / 4 weeks haloperidol decanoate.