Guanfacine for attention deficit hyperactivity disorder, June 2021
Page last updated: 5 November 2021
Drug utilisation sub-committee (DUSC)
June 2021
Abstract
Purpose
To review the utilisation of the Pharmaceutical Benefits Scheme (PBS) and Repatriation PBS (R/PBS) listed medicines used in the management of attention deficit hyperactivity disorder (ADHD). This includes a predicted versus actual analysis of guanfacine in the first 24 months of R/PBS listing.
Date of listing on the Pharmaceutical Benefits Scheme (PBS)
Guanfacine was first R/PBS-listed for this indication on 1 September 2018.
Data Source / methodology
The analysis used data from Services Australia supplied prescriptions database.
Key Findings
Over the seven year period 2014-2020:
- The number of prevalent patients treated with R/PBS medicines for ADHD has risen at a yearly average growth rate of 12.43%, however this rate does not give the full picture. From 2014-2017 the yearly average growth rate was 9.75%, whereas from 2018-2020 the yearly growth rate was 16%. The substantial increase since 2018 is likely to be due to the listing of guanfacine in September 2018.
- The number of prescriptions also increased at similar growth rates, from 2014-2017 the yearly average growth rate was 10.25%, whereas from 2018-2020 the yearly growth rate was 17.67%.
- The most commonly used medicine in terms of prevalent patients is the modified-release formulation of methylphenidate.
- For all age groups more males than females were treated. For >6 year olds, 76% of prevalent patients were boys and for 6-12 year 72% of prevalent patients were boys.
- Of all prevalent patients treated with R/PBS listed ADHD medicines:
- children under 6 years old account for 2% of patients
- children aged 6-12 years old account for 43% of patients
- adolescents aged 13-18 account for 22%
- adults aged 19+ account for 33%.
An analysis of medicine use in 2020 shows that:
- The majority of prescriptions were written by paediatricians or psychiatrists.
- The initial prescription of methylphenidate, lisdexamfetamine and dexamfetamine for the treatment of ADHD is generally restricted to specialists in most Australian states and territories.
- Rates of prescribing vary across states and territories, reflecting the different jurisdictional laws about stimulant prescribing. The rates of treatment in >6 year olds was highest in Tasmania (Tas) and lowest in the Australian Capital Territory (ACT), while rates in school-aged children (6-12 years old) were highest in Queensland (QLD) and Tas, and lowest in South Australia (SA). Rates of treatment for 13-18 year olds was highest in ACT and lowest in SA, while rates of treatment in adults were highest in Western Australia (WA).
Guanfacine:
- The listing of guanfacine in September 2018 has contributed towards an increase in the use of ADHD medicines. The listing of guanfacine has not resulted in substitution of ADHD medicines and thus a corresponding reduction in the use of other ADHD medications.
- 18,030 and 25,580 prevalent R/PBS patients were treated with guanfacine in 2019 and 2020 respectively.
- The total number of guanfacine prescriptions supplied in Year 1 (74,725) was more than double the predicted number (111%) with and even higher increase in in Year 2 (177,301) which was an increase of 255% over the predicted amount.
- A closer look at the distribution of the number of prescriptions per patient in the 12 months after initiation found that 11% of patients had one supply, while on average patients received 9.48 prescriptions in the first year of therapy.
- The expected cost offset from substitution of other ADHD medicines to guanfacine has not been realised
