Tokunaga H., Kudo K., Imamura T., Jitsufuchi N., Ohtsuka Y., Ikeda N.

Department of Forensic Medicine, Faculty of Medicine, Kyushu University 60, Fukuoka 812-82, Japan

In accordance with current psychiatric therapy, two or more kinds of antipsychotic drugs are usually prescribed. However, there are few data on the therapeutic plasma concentrations of antipsychotic drugs or on the correlation between daily dose and plasma concentrations, in cases where several antipsychotic drugs have been prescribed for each patient.
Methods. We measured the plasma concentrations of 9 antipsychotic drugs in 24 psychiatric impatients during a 6-month period. They were treated with fixed dosages of antipsychotic drugs. Plasma samples were collected early in the morning once a month, and the concentrations of antipsychotic drugs within the plasma were determined by gas chromatographv with nitrogen phosphorus detection, high-performance liquid chromatography (HPLC) with fluorescence detection and HPLC with UV detection.
Results. The plasma levels of chlorpromazine, levomepromazine, thioridazine, haloperidol, bromperidol, zotepine, oxypertine, sulpiride and sultopride were 21.8-92.4, 31.4-155.6, 101.4-202.7, 16.4-56.2, 2.7-11.7, 13.6-84.0, 29.9-80.4, 76.7-1138.0 and 35.7-2990.0 ng/ml, respectively. A linear correlation between daily dose and the plasma concentration of sultopride, levomepromazine, sulpiride, haloperidol, chlorpromazine and zotepine was noted.
Conclusion. The therapeutic plasma levels of 9 antipsychotic drugs were ascertained, and a linear correlation between daily dose and the plasma concentration was observed for 6 of these antipsychotic drugs.