After the introduction of tamper-resistant oxycodone in Australia, dispensing rates for higher-strength formulations decreased for people younger than 65 years, but there was no change in older adults, according to new research in CMAJ (Canadian Medical Association Journal).
Canada, the United States and Australia are the highest per capita consumers of opioids worldwide. Opioid use has increased 15-fold in Australia over 20 years (1992 to 2012), making it the country with the second highest per capita consumption of oxycodone. In 2014, the country introduced tamper-resistant controlled-release oxycodone.
The study looked at whether reformulation changed use of controlled-release oxycodone and opioid-related harms in a sample cohort of 36 528 adults who had at least one filled prescription for oxycodone during the study period (July 2012 to November 2016). After reformulation, dispensing of oxycodone in both 10-30 mg and 40-80 mg strengths gradually decreased for people under age 65 years, for total decreases of 11% and 31.5%, respectively. People younger than 65 years, especially those younger than 45 years, were more likely to switch to morphine after reformulation, and there was an increase in participants of all ages switching to oxycodone/naloxone.
"The observed decline in dispensing of higher-strength oxycodone controlled-release in participants less than 65 years of age may be due to an increase in switching to other strong opioids, chiefly morphine, rather than an increase in ending use," writes Dr. Andrea Schaffer, University of New South Wales, Sydney, Australia, with coauthors. "This is of concern because it suggests that people may be seeking out opioids without tamper-resistant properties."
The authors note that as the study was observational, the results do not indicate causation between reformulation and changes in behaviour, but rather an association.
Despite reductions in dispensing of stronger oxycodone, poisonings from injected oxycodone did not decrease, as measured by calls to the New South Wales Poison Information Centre, which receives about 50% of all poisoning calls yearly in Australia.
"We did not find an increase in ending use of strong opioids in parallel with an increase in switching to other non-tamper-resistant strong opioids," write the authors.
They note that people under age 65 who were using higher-strength opioids and switched to different types of opioids had been identified as having a higher risk of opioid use problems and should be closely monitored by their physicians.
The study was funded by Australia's National Health and Medical Research Council Centre of Research Excellence in Medicines and Ageing.
"Person-level changes in oxycodone use after the introduction of a tamper-resistant formulation in Australia" is published March 26, 2018.