Availability and use of non-prescribed buprenorphine-naloxone in a Canadian setting, 2014-2020.

Background: Buprenorphine-naloxone (BUP-NX) is a first-line treatment for opioid use disorder and has a superior safety profile compared to other forms of opioid agonist therapy. In Canada, restrictions on BUP-NX prescribing were relaxed in 2016, which may have had an effect on rates of diversion and non-prescribed use. We sought to longitudinally examine the reported availability and use of non-prescribed BUP-NX among people who use drugs (PWUD) in an urban Canadian setting.

Methods: We collected data from two linked prospective cohorts of PWUD in Vancouver, Canada, and examined self-reported availability and use of non-prescribed BUP-NX over time. We used a multivariable generalized estimating equations model to identify trends and factors associated with the immediate availability (i.e., within 10 min) of non-prescribed BUP-NX.

Results: Among 1617 participants between 2014 and 2020, the immediate availability of non-prescribed BUP-NX increased from 16% to 63% (p<0.001). In the multivariable analysis, factors independently associated with immediate BUP-NX availability included calendar year (adjusted odds ratio = 1.19, 95% confidence interval: 1.15-1.23), along with a number of other variables suggestive of more severe substance use disorders. Only 17 participants ever reported use of non-prescribed BUP-NX.

Conclusions: We observed that BUP-NX has become increasingly available in the unregulated drug supply in recent years but its use has remained infrequent in this setting. These results suggest that relaxed restrictions on BUP-NX prescribing have not been a major driver of increased non-prescribed use in this population.