Tardive dyskinesia and steady-state serum levels of thiothixene.

The purpose of this investigation was to determine the relationship between serum levels of the neuroleptic agent thiothixene and tardive dyskinesia in schizophrenics of a wide age range. Forty-one male schizophrenic subjects, 21 with tardive dyskinesia and 20 without, were given a fixed dosage of thiothixene hydrochloride (10 mg orally four times daily) after a drug-free period of one week. Higher steady-state serum levels of thiothixene (obtained after five days of a fixed-dosage schedule) were associated with greater degrees of tardive dyskinesia. This relationship was independent of the relationship between tardive dyskinesia and age.