Haloperidol Plasma Level Predicts Antipsychotic Efficacy in Schizophrenia

It has been noted repeatedly that as haloperidol plasma levels approach 15 ng/ml, dopamine D₂ receptors become saturated and antipsychotic efficacy seems to decline. This study amplifies the relation between haloperidol plasma levels, dose, and clinical response.

Researchers adjusted haloperidol doses to obtain two fixed haloperidol plasma levels (2 and 10 ng/ml) in 111 acutely-ill schizophrenic and schizoaffective patients. After a one-week placebo washout, patients were randomized to maintain one of the two plasma levels for three weeks and then randomized to maintain the other plasma level or continue at the same level for three more weeks. Sixty-five patients entered the first phase of active treatment and 30 patients entered the second …