The authors conducted a fixed-dose study of haloperidol blood levels and
clinical response in schizophrenic in patients and found that those with
steady-state RBC haloperidol levels in the range of 2.4--5.4 ng/ml showed
greater improvement than those with lower or higher levels. They found a
similar , although nonsignificant, curvilinear relationship between plasma
haloperidol levels and clinical response. These findings suggest that the
relationship between haloperidol blood levels and clinical response fits a
therapeutic window for the treatment of schizophrenia.