Use of antipsychotic medications in Australia between July 1995 and December 2001

Objective: To examine trends in the use of oral conventional, depot and atypical antipsychotic medications in Australia between July 1995 and December 2001. Method: For each six-month interval between July 1995 and December 2001, prescription data obtained from the Health Insurance Commission of Australia were converted into a measure of drug utilization expressed as the number of defined daily doses per thousand population per day (DDDs/1000/day). Results: Between July 1995 and December 2001, use of atypical medications increased from an estimated 0.27 to an estimated 3.83 DDDs/1000/day. Use of oral conventional medications decreased from 1.76 to 0.91 DDDs/1000/day, while use of depot medications decreased from 1.38 to 0.96 DDDs/1000/day. During the latter half of 2001, atypical medications accounted for 67.3%, oral conventional medications for 16.0%, and depot medications for 16.7% of total prescriptions for antipsychotic medications dispensed through community pharmacies in Australia. The increased use of atypical medications was accounted for largely by a dramatic increase in the use of olanzapine. Between July 2001 and December 2001, prescriptions for olanzapine accounted for 65.0% of total prescriptions for atypical antipsychotic medications. Conclusions: The results of the present study confirm that atypical antipsychotic medications have replaced conventional medications as the first-line pharmacological treatment for psychotic illness in Australia. While this change in prescribing practice is gratifying, the overwhelming preference for the use of olanzapine among clinicians prescribing antipsychotic medication is surprising and is of some concern given the significant increases in body weight that can accompany long-term use of this medication.