Average duration of treatment with antipsychotics among concession card holders in Australia.

OBJECTIVE: To analyse average treatment duration with antipsychotics reimbursed for concession card holders under the Pharmaceutical Benefits Scheme; the proportion of initial prescribing by general practitioners, psychiatrists and other physician; and the trend in drug choice in Australia.

METHOD: Based on a representative 10% sample of patients receiving Pharmaceutical Benefits Scheme prescriptions since 2005, antipsychotics redeemed by concession card holders in the period from 2010 to 2013 were analysed. A 5-year baseline period was used to exclude prevalent users from incident users. Treatment duration was estimated using the epidemiological equation: prevalence/incidence = average duration.

RESULTS: The overall average treatment duration was 3.0 years, ranging from 1.5 years in patients aged 75 years and older to more than 4 years among patients aged 25-64 years. The most commonly used antipsychotics were olanzapine, risperidone and quetiapine, with average duration of 2.9, 2.1 and 1.7 years, respectively. Amisulpride was used longest with an average duration of 3.7 years. Quetiapine is currently the most prescribed antipsychotic and the main antipsychotic prescribed by psychiatrists to new users. The increased prescribing of quetiapine among general practitioners explains the rapid increase in the overall use of quetiapine. General practitioners initiated therapy in about 70% of cases, while psychiatrists and other physicians in about 15% each. In children younger than 15 years of age, paediatricians initiated such treatment in 47%.

CONCLUSION: General practitioners both initiate and maintain treatment with antipsychotics for most adults, while paediatricians mainly begin such treatment in children. The substantial increase in use of quetiapine among general practitioners, along with the short treatment duration for quetiapine, strengthens a concern about antipsychotics increasingly used for less severe disorders. Increased collaboration between paediatricians and psychiatrists regarding the youngest and between general practitioners and psychiatrists or geriatricians regarding adults and older patients seems required.