Increases in controlled-release oxycodone utilisation following the subsidy of oxycodone with naloxone formulations: An Australian population-based study

Abstract

Purpose: Despite increasing use of oxycodone/naloxone controlled-release (CR) in Australia, little is known about how it has affected the overall oxycodone CR market since its subsidy in 2011.

Methods: We used Pharmaceutical Benefits Scheme dispensing claims (2006-2016) and interrupted time series analysis to examine changes in the quarterly rates of dispensing of oral oxycodone CR formulations (oxycodone/naloxone CR and single-ingredient oxycodone CR) and new oxycodone CR treatment episodes. We also performed a retrospective cohort study in a sample of people initiating a new oxycodone CR treatment episode in 2009, 2012/2013, and 2016 to compare opioid utilisation patterns over time.

Results: The subsidy of oxycodone/naloxone CR was associated with a 1.6-fold increase in the growth rate of oxycodone CR dispensing, resulting from rapid uptake of low strength (≤5 mg) oxycodone/naloxone CR. In our cohort of initiators, the number of new oxycodone CR treatment episodes increased 2.1-fold between 2009 and 2016; in 2016, 91.4% of new treatment episodes involved oxycodone/naloxone CR. Comparing 2016 with 2009, we observed an increase in people initiating with a tablet strength less than or equal to 5-mg (risk difference [RD] = 21.1%, 95% CI, 19.9%-22.4%) in people initiating with no other opioid dispensing 90 days prior to initiation (RD = 5.2%, 3.8%-6.6%) and with no further opioid dispensing 90 days after initiation (RD = 8.8%, 7.4%-10.2%).

Conclusions: After its subsidy, the uptake of low-dose oxycodone/naloxone CR was greater than expected if it were substituting the single-ingredient oxycodone CR, resulting in an expansion of the oxycodone CR market.

Keywords: Australia; drug utilisation; opioids; oxycodone; pharmacoepidemiology.

Figure 1.

Oxycodone CR tablets dispensed per 1,000 population per quarter, by strength and formulation Legend: Date of oxycodone/naloxone CR subsidy: December 1, 2011 (Q4 2011); date of introduction of tamper-resistant formulation and withdrawal of 5 mg single-ingredient oxycodone CR: April 1, 2014 (Q2 2014)

Figure 2.

New treatment episodes with oxycodone CR, by strength and formulation among concessional beneficiaries Legend: Date of oxycodone/naloxone CR subsidy: December 1, 2011 (Q4 2011); date of introduction of tamper-resistant formulation and withdrawal of 5 mg single-ingredient oxycodone CR: April 1, 2014 (Q2 2014). 2.5 mg/1.25 mg, 15 mg/7.5 mg and 30 mg/15 mg oxycodone/naloxone CR tablets were introduced in May 2016.