(120) A Multivariate Interrupted Time Series Analysis Assessing the Impacts of Half-Pack Sizes and Increased Access Restrictions on Publicly Subsidised Opioids in Australia

Sunday, August 28, 2022

8:00 AM – 1:45 PM CEST

Location: Hall C

Publication Number: 1165

Presenting Author(s)

Forrest C. Koch, BSc
– University of New South Wales, Sydney, New South Wales, Australia

Co-Author(s)

Jake Olivier
– School of Mathematics and Statistics, UNSW Sydney, Australia, Australia
Sallie-Anne Pearson, PhD
– Director, Centre of Research Excellence in Medicines Intelligence, Centre for Big Data Research in Health, Faculty of Medicine and Health, University of New South Wales, Sydney, Australia, New South Wales, Australia
Benjamin Daniels
– Centre for Big Data Research in Health, Kensington, New South Wales, Australia

Background: Regulators and payers globally are implementing measures to support the safe and appropriate use of opioids. In June 2020, the Pharmaceutical Benefits Scheme (PBS) subsidised half-pack sized immediate release (IR) opioids and introduced new prescribing restrictions for most IR and controlled release (CR) formulations. The changes were made to support the appropriate prescribing and use of opioids as well as to reduce the number of tablets circulating in the community.

Objectives: To evaluate the impact of introducing half-pack sizes and tightened prescribing restrictions on publicly-subsidised opioid dispensing in Australia.

Methods: We evaluated level and trend changes after June 2020 for 15 opioid formulations using a multivariate interrupted time series (MITS) analysis of oral morphine equivalents (OMEs) dispensed in a nationally representative 10% random sample of PBS beneficiaries over the period 04/02/2018 – 29/05/2021. The joint modelling of OMEs dispensed across multiple medicine classes allowed for efficient estimation of aggregated effects (IR, CR, overall) while controlling for common seasonal effects.

Results: From June 2020 we observed a level decrease of 20 ,980 OME/day (95%CI [11,164; 30,795]) overall, a reduction of 2.4% (95%CI [1.3%; 3.5%]) in all OMEs dispensed. IR and CR formulations accounted for a reduction of 11,749 OME/day (95%CI [6,674; 16,825]) and 9,230 OME/day (95%CI [1,995; 16,466]), respectively. The largest reductions occurred in CR oxycodone and naloxone (6,146 OME/day, 95%CI [2,496; 10,013]), IR paracetamol and codeine (5,490 OME/day 95%CI [4,612; 6,309]), and IR tramadol (4,047 OME/day, 95%CI [3,789; 4,290]). No significant changes in trend were detected when aggregating across IR formulations (14.8 OME/day^2 , p=.156), CR formulations (-10.1 OME/day^2, p=.628), or overall (4.7 OME/day^2, p=0.905).

Conclusions: The introduction of half-pack sizes and tightened prescribing restrictions were associated with declines in both IR and CR opioid dispensings on the PBS. These findings align with the intent of the policy intervention, but it is not possible to determine if this represents a true reduction in Australian opioid use as patients may have accessed these medicines through the private market.