The relationship between plasma and red blood cell neuroleptic levels, oral dosage, and clinical parameters in a chronic schizophrenic population.

: Neuroleptic drug levels were determined in plasma and RBC in 63 subjects on various neuroleptic drugs using a radioreceptor binding assay. There was a correlation between oral dose in chlorpromazine equivalents and plasma level (r = 0.31, p less than .01). The correlation between dose and plasma level and ratios of plasma level to dose varied by drug. RBC neuroleptic concentration was not related to dosage. In a group of 25 chronic schizophrenic inpatients, plasma level was significantly curvilinearly related to total BPRS. For subjects with plasma levels below 25 ng haloperidol/ml, BPRS total and thought disorder subscores were negatively correlated to plasma level (p less than 0.02). RBC drug concentration was not related to psychopathology. For six of seven subjects, changes in medication based on plasma level resulted in some clinical improvement. Data are presented on the inter- and intraassay variability and other factors which affect the clinical usefulness of the radioreceptor assay.