Increasing Clozapine Dispensing Trends in Queensland, Australia 2004–2013

Abstract

Introduction: Clozapine is the most effective treatment for treatment-resistant schizophrenia but its use is suboptimal.

Methods: Clozapine dispensing data from Queensland, Australia were extracted (2004–2013). The number of people dispensed clozapine each year and mean maintenance doses were calculated. The 18-week and 5-year cessation and treatment interruption rates were calculated using Kaplan-Meier analysis.

Results: Clozapine dispensings increased 36.4% (p<0.001) from 44 to 60 people per 100 000. This was estimated as 8.3% of people with schizophrenia and 33.3% of people with treatment resistant schizophrenia dispensed clozapine in 2013. Mean maintenance dose did not significantly change (364–399 mg) over 5 years of treatment. One in 7 (14.2%) people ceased within the first 3 weeks. 3-quarters (72.7%) reached maintenance therapy. The 5-year actuarial estimate of the proportion of people a) dispensed clozapine was 0.610 (S.E. 0.011) and b) with an interruption to treatment was 0.422 (S.E. 0.013).

Discussion: The number of patients being dispensed clozapine increased between 2004 and 2013 but clozapine is still underused. Increased use combined with continued monitoring for adverse effects will improve quality use of clozapine.

Key words

clozapine - antipsychotic - pharmacoepidemiology - schizophrenia

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