No results are conclusive and all are based on small, short, studies. It would be understandable, however, if clinicians were cautious in prescribing doses in excess of 7.5 mg/day of haloperidol to a person with uncomplicated acute schizophrenia, and if people with schizophrenia were equally reticent to take greater doses. Further research is needed regarding the efficacy and tolerability of the >1.5-3.0 mg/day dose range.
Plasma haloperidol levels and clinical effects in schizophrenia and schizoaffective disorder.
Plasma haloperidol levels between 5 and 11 ng/mL may be clinically optimal for acutely exacerbated schizophrenia, but the evidence for this therapeutic window has been inconsistent.
                Haloperidol was administered in a double-blind manner during two consecutive 3-week experimental periods to 65 patients with acutely exacerbated schizophrenia or schizoaffective disorder. Two plasma levels were targeted: "low" (2 ng/mL) and "moderate" (10 ng/mL). The subjects were randomly assigned to four treatment sequences (low-low, low-moderate, moderate-moderate, or moderate-low).
                In the first 3 weeks, the antipsychotic efficacy of haloperidol increased with plasma levels up to approximately 12 ng/mL. In the second 3 weeks, decrease of plasma levels reduced negative symptoms.
                For most patients, plasma levels not exceeding 12 ng/mL yield the best results in the first 3 weeks of treatment. Subsequent lowering of the plasma levels may improve negative symptoms.