The clinical use of plasma clozapine levels in a maximum security setting

Background. Research suggests a correlation between clozapine dose, plasma level and therapeutic response. Plasma clozapine levels may, therefore, be useful in practice. Little evidence exists, however, on the indications for, and outcome of, levels being undertaken or their use in maximum security settings. Objective. To determine if plasma clozapine levels are useful in clinical practice by analysing their use at the maximum-security State Hospital, Carstairs. Methods. All plasma clozapine levels (until March 2004) undertaken at the State Hospital, clinical indication and outcome were analysed by retrospective case note analysis. These results were compared with the published literature. Results. A total of 140 plasma clozapine levels were analysed. The average level was 0.61 mg/l and dose was 622.9 mg/day. The indications for and consequences of levels are demonstrated. A positive correlation of 0.217 was calculated. Conclusion. This paper shows that plasma clozapine levels are most useful in managing side effects and suspected non-compliance. Plasma clozapine levels are, therefore, useful in clinical practice.