Comparative efficacy of red cell and plasma haloperidol as predictors of clinical response in schizophrenia

The relative utility of steady-state (SS), plasma (Pl), and red blood cell (RBC) haloperidol levels for predicting clinical response was evaluated in a fixed-dose study in schizophrenic inpatients. There were significant curvilinear relationships between the decrease in BPRS Psychosis Factor Scores by day 24 of haloperidol treatment and both Pl (R²=0.34) and RBC (R²=0.38) haloperidol levels. Although SS RBC haloperidol levels consistently showed a slightly stronger relationship to clinical response than Pl levels. in several comparisons, the differences in R²s between Pl and RBC haloperidol were not statistically significant. Ninety percent confidence intervals for the blood level ranges associated with optimal clinical response in our sample of patients were: 6.5–16.5 ng/ml Pl haloperidol and 2.2.–6.8 ng/ml RBC haloperidol.