Blood levels of haloperidol and clinical outcome in schizophrenia.

Haloperidol levels in blood were measured in 55 acutely psychotic inpatients with schizophrenia, who were randomly assigned to three fixed doses of oral haloperidol. Nineteen of these subjects received 10 mg/day, 18 received 30 mg/day, and 18 of them received 80 mg/day. All of the subjects were treated under double-blind conditions for 6 weeks or until remission. Haloperidol and reduced haloperidol levels were measured in plasma and red blood cells at the end of 2, 4, and 6 weeks of treatment. There were statistically significant linear correlations between the dose of haloperidol and levels in blood. An examination of data for linear and curvilinear relationships between levels in blood and clinical response did not yield any statistically significant relations. The data did not support the concept of a "therapeutic window." The ratio of reduced haloperidol to haloperidol levels in plasma or red blood cells did not yield any statistically significant correlations to clinical outcome.