The concept of the neuroleptic threshold: an update

The authors review the development and the controversies of the neuroleptic threshold theory. According to this theory, the minimum effective antipsychotic dose of a neuroleptic ("threshold dose") correlates with the appearance of "fine motor" symptoms (micrography) as opposed to the appearance of manifest or "coarse motor" extrapyramidal side effects. About half of the acutely exacerbated schizophrenic patients respond to threshold doses, but no predictors are known to characterize the responders. The neuroleptic threshold doses were found to be low, and the low dose treatment strategy is supported by the results of current PET and neuroleptic plasma level studies.