Therapeutic drug monitoring (TDM) and clinical outcomes in forensic patients under clozapine therapy compared to therapies with other antipsychotic drugs

Introduction: The aim of this retrospective study was to examine dosage, serum concentration, dose-related plasma concentration and forensic clinical outcomes under therapy with clozapine and other antipsychotic drugs in comparison. Methods: The study analyzed medical files of 69 forensic patients aged 19–62 years and treated with clozapine in the years 1985–2011. Forensic clinical outcome was compared during one year under clozapine therapy to one year treatment with other antipsychotic drugs, with regard to dosage, serum concentration and dose-related plasma concentration. Results: Under clozapine therapy 86.9% were treated with recommended dosages of 100–600mg/day, 44.9% were within the therapeutic reference range and 67.2% were within the expected dose-related plasma concentration. Under other antipsychotic therapies 67.5% were treated with recommended dosages, 68.2% were within the therapeutic reference range and 34.9% were within the dose-related plasma concentration range. Considering the changes in privilege level in forensic patients under clozapine therapy there was an improvement of more than 50% compared to other antipsychotic therapies. Conclusions: 1. Treatment with clozapine seemed likely to be more effective to reduce the risk of violence and aggression than treatment with other antipsychotic drugs. 2. The improvement was obtained by doses and plasma concentrations which are recommended to general psychiatric patients.