Restricting PBS prescribing rules in 2020 led to a significant decline in dispensing of subsidised opioids, but a rise in private scripts, an independent study has concluded.

While the findings suggest that opioid use declined overall in Australia as a result of the clampdown aimed at chronic non-cancer pain treatment, this would have been greater were it not for some patients shifting to unsubsidised medicines, according to the authors.

Their study examined the impact of regulations introduced in June 2020 which restricted the number of repeat prescriptions, introducing half pack sizes, and increasing the level of authorisation required to prescribe some opioids, among other changes to PBS rules.

These restrictions – aligned with changes made by TGA – aimed to minimise harms associated with prescribed opioids for chronic pain in the community by reducing the number of prescriptions and the number of people prescribed opioids unnecessarily.

The research team used a 10% sample of PBS claims data and records from the IQVIA database of wholesale pharmacy medicine sales to calculate trends across the two years prior to the revamp and the following 12 months.

This revealed a 3.8% reduction in PBS-subsidised opioid medicine dispensing to June 2021, compared with expected trend numbers, the researchers reported in the MJA (link here).

Findings showed the biggest falls in immediate release (IR) formulations, which fell 8.4% below trend, while dispensing of controlled release was only 2.6% lower than would have been expected.

However, the analysis of wholesale medicine sales showed there had been a more limited decline overall, just 0.9% below trend which was not statistically significant, the authors said.

“Total sales of these medicines did not change significantly after 1 June 2020, which could indicate a shift from public to private prescriptions; however, a large proportion of codeine/paracetamol and tramadol prescribing was on private prescriptions even before the PBS changes,” they wrote.

“Changes in overall sales would not be expected to perfectly match PBS-subsidised dispensing changes, and changes in the proportion of PBS-subsidised dispensing with respect to total sales (ie, consistent with a shift to private prescriptions) were statistically significant only for tramadol IR.”

On the other hand, there was no evidence of a “broad move from public to private prescribing”, suggesting the reductions in PBS dispensing reflected reduced overall use, they stressed.

And the declines came against an overall downward trend in sales, which had been in evidence even prior to the new restrictions, according to the team.

Most opioids, including controlled-release formulations, saw decreases in use through the PBS following the changes. The one exception was the newest opioid medicine, tapentadol.

“The use of most opioids has been declining over the past five or so years, but tapentadol has been going in the other direction during that time,” said study co-senior author Dr Benjamin Daniels, a Senior Research Fellow and Cancer Institute NSW Early Career Fellow from UNSW’s Medicines Intelligence Research Program.

Tapentadol was listed on the PBS in 2014 and it’s common for the use of newer medicines to increase until the market has matured, he noted.

“When these changes to the PBS came into effect, that upward trajectory levelled off on the PBS, but sales of instant-release formulations – which aren’t available through the PBS – jumped up by over 9 per cent,” he said.

Dr Daniels added that the team suspected that COVID-19 may help explain this jump, given the temporary ban on elective surgeries decreased opioid sales between March and May in 2020, but more research was needed explain the shift.