Patterns of antipsychotic medication use in Australia 2002-2007

Objective: Atypical antipsychotic medications that are primarily used to treat schizophrenia and bipolar disorder cost the Pharmaceutical Benefits Scheme (PBS) AUD$334.4m in 2007. There are indications that they have also been used outside the approved indications to treat behavioural disturbances in the elderly. The aim of the present study was therefore to examine (i) trends in prescribing of subsidized atypical antipsychotic drugs in the Australian population from 2002 to 2007; and (ii) gender and age differences in the utilization of these drugs. Methods: Government (Medicare Australia) data on numbers of prescriptions, quantity and doses for atypical and typical antipsychotics from 2002 to 2007 were analysed. Defined daily dose per 1000 population per day were estimated for age and sex groups using Australian Bureau of Statistics population data. Results: The proportion of prescribed antipsychotics that were atypical increased from 61% in 2002 to 77% in 2007. In male subjects, olanzapine was most often prescribed between the ages of 25 and 55 years. In female subjects, in contrast, the highest rates of prescribing were in those >= 75 years. Lower doses of these drugs were prescribed in older adults. Conclusions: Atypical antipsychotic drugs were most commonly used to treat schizophrenia in younger men and behavioural disturbances in older women with dementia. They appear to have been used outside of the approved indication for schizophrenia and bipolar disorder with significant financial costs to the PBS. Research into the reasons for their extensive use in elderly women is needed to inform more rational prescribing of these medicines.