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ID: 120

Type of submission: Oral

Conference track: Research

Topics: Harm Reduction for Non-Injectors and/or Stimulant Users; Opioid Substitution Therapy Programmes

Presenting author: Anna Palmer

Presenting author biography:

Anna Palmer recently completed her Bachelor of Biomedical Science Honours at Monash University with the Burnet Institute, studying patterns of methamphetamine use amongst people who inject drugs in Melbourne, Australia

The effect of opioid substitution therapy on methamphetamine use in a cohort of people who inject drugs: a mixed methods study

Anna Palmer, Nick Scott, Paul Dietze, Peter Higgs

Background: Opioid Substitution Therapy (OST) is a well-established drug treatment for people dependent on opioids, shown to reduce both opioid use and opioid-related harms. Methadone is the most commonly prescribed treatment in Australia, however buprenorphine/naloxone is also available. In the wake of a recent crystal methamphetamine “epidemic” in Australia and various crystal methamphetamine “epidemics” around the globe, the relationship between OST and methamphetamine use by people who inject drugs (PWID) needs to be understood. In this study we explored the relationship between OST and methamphetamine use in a community-based sample of PWID in Melbourne, Australia.

Methods: Longitudinal data from 757 community-recruited participants from the Melbourne Injecting Drug User Cohort Study (MIX) were used to measure associations between OST and methamphetamine use, and fourteen in-depth interviews with purposively selected participants from MIX further explored the relationship between OST and methamphetamine use.

Results: Our analyses showed that being on OST decreased the odds of reporting past month methamphetamine use (AOR=0.64, 95% CI 0.46-0.91), but this varied by OST type with participants on buprenorphine/naloxone at an increased risk of reporting methamphetamine use compared to those on methadone (AOR=2.23, 95% CI 1.01-4.94). Interviews revealed a complex physical and psychological relationship between participants’ opioid dependency and their use of methamphetamine. Many participants reported that the reduced effect of heroin toxicity whilst on buprenorphine/naloxone was the main reason for their use of methamphetamine, with most participants reporting that they still used heroin whilst on methadone treatment.

Conclusion: There is a complex physical and psychological relationship between OST and methamphetamine use, particularly when considering the differing effect of methadone and buprenorphine/naloxone treatments. Understanding these findings has important implications for the promotion of harm reduction interventions.