Increases in controlled-release oxycodone utilisation following the subsidy of oxycodone with naloxone formulations: An Australian population-based study
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2019-01-01
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Pharmacoepidemiology and Drug Safety
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WILEY
Melbourne Authors
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Centre for Youth Mental Health
Melbourne School of Population and Global Health
Melbourne School of Population and Global Health
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Conference Paper
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Schaffer, A. L., Karanges, E. A., Buckley, N. A., Wilson, A., Degenhardt, L., Larance, B. & Pearson, S. A. (2019). Increases in controlled-release oxycodone utilisation following the subsidy of oxycodone with naloxone formulations: An Australian population-based study. Pharmacoepidemiology and Drug Safety, 28, (1), pp.97-105. WILEY. https://doi.org/10.1002/pds.4683.
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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.