Post-marketing surveillance of buprenorphine-naloxone in Australia: diversion, injection and adherence with supervised dosing.

BACKGROUND: These studies compared the diversion and injection of buprenorphine-naloxone (BNX), buprenorphine (BPN) and methadone (MET) in Australia.

METHODS: Surveys were conducted with regular injecting drug users (IDUs) (2004-2009, N=881-943), opioid substitution treatment (OST) clients (2008, N=440) and authorised OST prescribers (2007, N=291). Key outcome measures include the unsanctioned removal of supervised doses, diversion, injection, motivations, drug liking and street price. Levels of injection among IDUs were adjusted for background availability of medications. Doses not taken as directed by OST clients were adjusted by total number of daily doses dispensed.

RESULTS: Among regular IDUs, levels of injection were lower for BNX relative to BPN, but comparable to those for MET, adjusting for background availability. Among OST clients, fewer BNX clients (13%) reported recently injecting their medication, than BPN (28%) and MET clients (23%). Fewer MET clients (10%) reported removal of supervised doses, than BPN (35%) and BNX clients (22%). There were no differences in prevalence of recent diversion (28% of all OST clients). Adjusting for the total doses dispensed, more BPN was injected (10%), removed (12%) and diverted (5%), than MET (5%, <1% and 2% respectively) and BNX (5%, 9% and <1% respectively). In 2009, the median street price of BNX was equivalent to that for BPN.

CONCLUSIONS: BNX was less commonly and less frequently injected than BPN, but both sublingual medications were diverted more than liquid MET.