[ 123I]IBZM SPECT in patients treated with typical and atypical neuroleptics: relationship to drug plasma levels and extrapyramidal side effects

• Published in: Psychiatry research 1997-09, Vol.75 (2), p.103-114
• Main Authors: Schlösser, R., Schlegel, S., Hiemke, C., Nickel, O., Bockisch, A., Rao, M.L., Hahn, K.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Antipsychotic Agents - adverse effects; Antipsychotic Agents - classification; Antipsychotic Agents - therapeutic use; Antipsychotics; Basal Ganglia Diseases - chemically induced; Basal Ganglia Diseases - diagnostic imaging; Benperidol; Benperidol - adverse effects; Benperidol - therapeutic use; Benzamides; Biological and medical sciences; Bipolar Disorder - diagnostic imaging; Bipolar Disorder - drug therapy; Brain - diagnostic imaging; Brain - drug effects; Clozapine; Clozapine - adverse effects; Clozapine - therapeutic use; Corpus Striatum - diagnostic imaging; Corpus Striatum - drug effects; Depressive Disorder, Major - diagnostic imaging; Depressive Disorder, Major - drug therapy; Dopamine; Dopamine Antagonists; Dose-Response Relationship, Drug; Female; Frontal Lobe - diagnostic imaging; Frontal Lobe - drug effects; Haloperidol; Haloperidol - adverse effects; Haloperidol - therapeutic use; Humans; Male; Medical sciences; Middle Aged; Neurologic Examination - drug effects; Neuropharmacology; Pharmacology. Drug treatments; Psychiatric Status Rating Scales; Psycholeptics: tranquillizer, neuroleptic; Psychology. Psychoanalysis. Psychiatry; Psychopharmacology; Pyrrolidines; Receptors, Dopamine D2 - drug effects; Schizophrenia, Paranoid - diagnostic imaging; Schizophrenia, Paranoid - drug therapy; Single photon emission computed tomography; Tomography, Emission-Computed, Single-Photon
• ISSN: 0925-4927; 0165-1781; 1872-7506; 1872-7123
• DOI: 10.1016/S0925-4927(97)00044-9

[ 123I]Iodobenzamide (IBZM) is an iodine-labeled dopamine receptor ligand and can be used to visualize brain D 2 receptors in humans with single photon emission computerized tomography (SPECT). The ratio of striatal IBZM uptake to uptake in frontal cortex (ST/FC ratio) represents a semiquantitative measure of D 2 receptor binding in the striatum. Our study sample included six patients treated with haloperidol (3.0–8.0 mg/day orally; one patient with an average of 0.9 mg/day intramuscularly), five patients with benperidol (9.0–15.0 mg/day orally) and nine patients treated with clozapine (200.0–600.0 mg/day orally). Typical neuroleptics (TNs) and atypical neuroleptics (ANs) were significantly different in their ST/FC ratios. The ST/FC ratios indicated that patients treated with benperidol exhibited the lowest ST/FC ratios, with increasingly higher ratios in patients on haloperidol or clozapine. We found a curvilinear relationship between the ST/FC ratios and the dose/kg body wt. of TNs and ANs on the basis of a dose-normalization according to K i -values of the neuroleptic at D 2 receptors and a weaker, but also curvilinear relationship between ST/FC ratios and normalized dosages according to clinically defined chlorpromazine equivalents. The specific uptake of IBZM did not correlate with the plasma levels of the TN haloperidol at the present dose range (0–12.4 ng/ml). For clozapine, a meaningful negative correlation between plasma levels and ST/FC ratio could be established. There was a negative continuous correlation between uptake of IBZM and extrapyramidal side effects, which is different from the threshold-based relationship between extrapyramidal side effects and IBZM uptake reported previously.