Correction of serum neuroleptic activity for blood-to-brain distribution: a method that may render radioreceptor assay results comparable between neuroleptics.

Serum neuroleptic activity by radioreceptor assay and prolactin concentration were measured every 6 months for 2 years in 105 male schizophrenic outpatients. The patients took a variety of neuroleptics at clinically determined doses. As expected, when four dissimilar neuroleptics were examined together, there was no significant correlation between serum neuroleptic activity and either equivalent neuroleptic dose or serum prolactin concentration. Moderate correlations were seen, however, when neuroleptic activity was standardized between neuroleptic drugs. Similar moderate correlations were seen when neuroleptic activity was corrected for the blood-to-brain distribution of each neuroleptic. These two correction techniques ranked corrected neuroleptic activity in very similar orders. Correction for blood-to-brain distribution may be a practical way to compare serum neuroleptic activity from different neuroleptics.