Serum level monitoring of thiothixene in schizophrenia: acute single-dose levels at fixed doses.

After establishing a strong correlation between steady-state thiothixene levels and levels drawn 2.5 hours after a 20-mg test dose, the authors examined the correlation between clinical improvement and serum levels drawn 2.5 hours after a single 20-mg test dose of thiothixene. For 30 male schizophrenic inpatients, improvement on the Brief Psychiatric Rating Scale was significantly correlated with the single test-dose levels. Serum levels were also positively correlated with age, which may explain the tendency of elderly patients to require lower neuroleptic doses and to exhibit a higher incidence of side effects. The results suggest that acute single-dose levels may be useful in predicting clinical response to thiothixene.