Objective: To compare the efficacy of clozapine with typical antipsychotic drugs in controlling impulsivity and to explore the possible correlation of impulsivity with plasma 5-hydroxytryptamine (5-HT) levels, plasma 5-hydroxyindoleacetic acid (5-HIAA) levels and plasma 5-HT turnover.
Design: Prospective, cross-sectional study open to medication and blinded to biochemical analyses.
Participants: Healthy control subjects (n = 24) and 46 inpatients and outpatients meeting the DSM-IV criteria for schizophrenia; 20 were being treated with clozapine and 26 were taking typical antipsychotic drugs.
Interventions: All psychotropic drugs other than clozapine or typical antipsychotic drugs were discontinued for at least 5 days and subjects fasted overnight before they were assessed.
Outcome measures: Coccaro Impulsivity Scale scores, plasma 5-HT levels, 5-HIAA levels and 5-HT turnover.
Results: Patients treated with clozapine and those treated with typical antipsychotics had significantly higher impulsivity scores than the control group, and the mean impulsivity 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 the other 2 groups. 5-HT turnover was significantly higher for the 2 drug-treatment groups than for the control group.
Conclusions: These results suggest that treatment with clozapine should be considered for patients with schizophrenia who are impulsive and aggressive.