Serum concentration of depot neuroleptics in tardive dyskinesia.

Using radioimmunoassay techniques, serum levels of depot neuroleptics, fluphenazine and flupenthixol, were estimated in two groups of chronic schizophrenic patients with, and without, tardive dyskinesia. There were high significant difference in dose-related serum levels of either drug between the groups. The hypothesis that patients with tardive dyskinesia develop the syndrome because they do not metabolise neuroleptics as efficiently as those without the syndrome was not supported by the data.