Neuroleptic drug levels and therapeutic response: preliminary observations with red blood cell bound butaperazine

The authors studied neuroleptic concentration-therapeutic response curves for butaperazine (BPZ), a piperazine phenothiazine, in 10 schizophrenic patients during the first 12 days of treatment. BPZ bound to red blood cells (RBC) was more strongly correlated with therapeutic response than was plasma BPZ. RBC BPZ concentrations could be used to define a "therapeutic window", an optimun concentration for therapeutic response, above and below which favorable response diminishes. The authors emphasize the preliminary nature of the data but suggest that levels of RBC-bound neuroleptic may provide an important guide for dosage regulation in schizophrenic patients.