Haloperidol blood levels and effects in schizophrenia and schizoaffective disorder: a progress report.

To test the hypothesis of a "therapeutic window," we have randomly assigned acutely exacerbating schizophrenic or schizoaffective patients to one of three plasma levels of haloperidol (HAL): 2-13, 13.1-24, or 24.1-35 ng/ml. Patients who did not improve after 6 weeks of this treatment were randomly assigned to one of the three haloperidol levels for another 6 weeks. The improvement was defined as at least 50 percent reduction of the Brief Psychiatric Rating Scale (BPRS) total score. The results obtained in 111 patients do not support any consistent relationship between plasma level of haloperidol and clinical improvement. Patients in the high haloperidol plasma range tended to have more side effects. These results suggest that the haloperidol doses used in clinical practice may be higher than necessary.