Effects of clozapine and typical antipsychotic drugs on plasma 5-HT turnover and impulsivity in patients with schizophrenia: a cross-sectional study

To compare the efficacy of clozapine with typical antipsychotic drugs in co ntrolling impulsivity and to explore the possible correlation of impulsivit y with plasma 5-hydroxytryptamine (5-HT) levels, plasma 5-hydroxyindoleacet ic acid (5-HIAA) levels and plasma 5-HT turnover. Design: Prospective, cros s-sectional study open to medication and blinded to biochemical analyses. P articipants: Healthy control subjects (n = 24) and 46 inpatients and outpat ients meeting the DSM-IV criteria for schizophrenia; 20 were being treated with clozapine and 26 were taking typical antipsychotic drugs. Intervention s: All psychotropic drugs other than clozapine or typical antipsychotic dru gs were discontinued for at least 5 days and subjects fasted overnight befo re they were assessed. Outcome measures: Coccaro Impulsivity Scale scores, plasma 5-HT levels, 5-HIAA levels and 5-HT turnover. Results: Patients trea ted with clozapine and : those treated with typical antipsychotics had sign ificantly higher impulsivity scores than the control group, and the mean im pulsivity score of the typical antipsychotic group was significantly higher than that of patients treated with clozapine. The mean concentration of 5- HT of the typical antipsychotic group was significantly lower than that of the control group and patients treated with clozapine; however, mean plasma levels of 5-HIAA were significantly higher for the clozapine group than th e other 2 groups. 5-HT turnover was significantly higher for the 2 drug-tre atment groups than for the control group. Conclusions: These results sugges t that treatment with clozapine should be considered for patients with schi zophrenia who are impulsive and aggressive.