D2-DOPAMINE RECEPTOR OCCUPANCY DIFFERS BETWEEN PATIENTS WITH AND WITHOUT EXTRAPYRAMIDAL SIDE-EFFECTS

To investigate whether the occurrence of extrapyramidal side effects w as related to D2 dopamine receptor occupancy, iodobenzamide single pos itron emission computed tomography was carried out in 27 schizophrenic patients and 10 controls. Eighteen patients were treated with haloper idol; 9 patients were treated with clozapine. Our data suggest a relat ionship between D2 receptor occupancy and extrapyramidal side effects as well as the existence of a neuroleptic threshold of a striatal:fron tal cortex ratio of 1.2, below which drug-induced exptrapyramidal side effects can be expected.