Clozapine use pattern in persons with and without treatment for Parkinson's disease in real-world conditions: a naturalistic study in a community-based sample

ObjectiveTo explore the pattern of clozapine use in persons with severe mental illness and in persons with Parkinson's disease and the characteristics associated with early discontinuation in naturalistic conditions. MethodA historical fixed cohort study of persons newly treated with clozapine was performed on a representative community-based sample of persons affiliated to the French health insurance system (n=611393). Treatment for Parkinson's disease was used as a proxy for this condition and lack of such treatment as a proxy for severe mental illness (SMI). ResultsThe prevalences of antipsychotic and clozapine use were 4.4% and <0.1% respectively. Of the 237 persons with a new outpatient prescription of clozapine, 25% were prescribed an antiparkinsonian treatment. In persons with SMI, the median duration of the index episode of clozapine treatment was 4.9months (Interquartile range 1.0-20.5). Longer duration was independently associated with coprescription of anxiolytics or antidepressant. Few new additions of antipsychotics were observed during the clozapine episode. ConclusionEfforts have to be made to optimize clozapine treatment in real-world conditions. Considering the high frequency of persons with Parkinson's disease among clozapine users, further studies have to be performed in this population.