Examining the dispensing patterns of antipsychotics in Australia from 2006 to 2018 - A pharmacoepidemiology study

Antipsychotic medications can be prescribed in Australia by medical and nurse practitioners under the Pharmaceutical Benefits Scheme (PBS). The current pharmacoepidemiology study aims to determine the dispensing rates of antipsychotic medicines in Australia, and to produce and examine a time-trend of the dispensing patterns of these medicines.

Dispensing counts of antipsychotic medication from 2006 to 2018 were accessed from the PBS dataset. All of the antipsychotic medicines dispensed were included for time trend analysis. Cumulative dispensing counts and defined daily dose (DDD) per 1000 concessional population days (DPD) were analysed for the purpose of time trend analysis.

Sixteen antipsychotic medications were assessed and had a total cumulative dispensing count of 33, 732, 404. Olanzapine had the highest cumulative prescription count and Quetiapine experienced the highest average dispensing count and rate as determined by DPD. Twelve out of the sixteen medications were second-generation antipsychotics (SGAs). Overall, eleven out of the sixteen medications (aripiprazole, asenapine, brexpiprazole, clozapine, flupentixol, lurasidone, olanzapine, paliperidone, quetiapine, ziprasidone, zuclopenthixol) had an increase in both dispensing count and rate, as expressed per DPD.

The current study highlights the increasing prescription rates of SGAs and the stagnation of FGA prescription among Australian health practitioners. This is observed through particularly large increase in the dispensing rates of Olanzapine and Quetiapine. Further interdisciplinary investigation is required to ensure that these medications are being prescribed under the appropriate medical rationale, particularly to groups that are vulnerable to the adverse effects of the medications.