Antipsychotics in the middle aged, February 2013 & June 2013
A Report prepared by the Drug Utilisation Subcommittee (DUSC) of the Pharmaceutical Benefits Advisory Committee (PBAC)
Abstract
The use of atypical antipsychotics in adults aged 20–59 years in Australia is increasing without a proportionate increase in the prevalence of currently subsidised indications. Use of selected antipsychotics in depression and anxiety disorders has been reported in the literature. In addition use of low dose quetiapine is reported as a sedative. In Australia the three most commonly used antipsychotics are quetiapine, olanzapine and risperidone. While much work has been done on elderly patients the increasing use of these drugs in middle aged people is also of concern given the lack of data for both benefits and harms for some reasons for prescribing. This study examines the patterns of utilisation of PBS-listed antipsychotics in middle aged patients in Australia.
De-identified patient level pharmacy claim data from 1 December 2010 to 31 December 2012 was extracted from the records of subsidised claims provided to the Australian Government by dispensing pharmacies. As the number of records was very large a 10% sample of the dataset was used for some analyses. Data elements extracted for each de-identified record were age at date of supply, gender, medicine form and strength. Prescriber type was determined from the de-identified prescriber approval number. Initiation to treatment was the first drug supply after a minimum of 12 months previously. Co-administration was assumed where the days of coverage of both drugs were evident based on dates of supply.
Use of antipsychotics increased from around 20 patients/1000 in the 20–24 year age population to a maximum of 36 patients/1000 aged 34–39 and 40–45 years respectively. More males received antipsychotics until aged 50. After this a larger proportion of treated patients were females. Quetiapine was the most commonly prescribed antipsychotic in all age groups. Quetiapine use has grown by 82% from 2008 to 2011 while there were small reductions in olanzapine (-3%) and risperidone (-6%). The most commonly used treatment regimen in all age groups was an antidepressant co-administered with quetiapine, with a trend to increase with age.
For the 155,630 patients receiving any antipsychotic in 2011, 37.6% received quetiapine. Around 23% of these people received prescriptions for quetiapine 25 mg without any other quetiapine strengths, about 2/3 of these in a regimen with an antidepressant and the remaining 1/3 as one single strength antipsychotic.
Quetiapine 25 mg, supplied in a pack of 60, was usually refilled around 26 days but there was a significant second peak refilling at around 60 days. This is indicative of one 25 mg tablet daily for a substantial number of people. GPs were the most common prescribers of original prescriptions for antipsychotics however it is not possible to show if this was on advice of a psychiatrist.
The patterns of prescribing antipsychotics show differences that suggest different factors in patient selection. The study showed higher than expected use of quetiapine 25 mg as a single agent, possibly related to its sedative properties and as an agent to treat anxiety. Additional use may be as either adjunctive treatment in depression or treatment to manage side effects of antidepressants. The harms associated with antipsychotics are well documented, although less so for low dose preparations. The evidence supporting antipsychotics as adjunctive treatments in major and refractory depression does not completely support the increasing use of quetiapine 25 mg in the community seen in the utilisation data. While the median age of onset for depression occurs in the mid-30s and therefore some use of antipsychotics is to be expected in this age group the high use of low dose quetiapine is poorly supported by the literature. Prescribers may not be aware of the long term harm risk. The perception of low-dose antipsychotics as ‘safer’ medicines than other medicines such as benzodiazepines as narcotics and anti-anxiety agents are poorly supported in the literature and more research needs to be done in some patient groups.
