Aims: We report on motivations for crystal methamphetamine-opioid co-use/co-injection through narratives of people who inject drugs during a period of increased crystal methamphetamine use reporting in Australia.

Methods: Fourteen in-depth interviews were undertaken with selected participants (12 male, 2 female) from the Melbourne Injecting Drug User Cohort Study, including those in and out of opioid substitution therapy (OST).

Results: The main motivations for co-use reported by participants were as follows: (1) that heroin could be used to reduce the negative side effects of heavy crystal methamphetamine use, particularly during the ‘comedown’ phase; (2) that small quantities of crystal methamphetamine used with heroin could prolong the intoxication effect of heroin, and hence the time before opioid withdrawal; (3) that co-injection of crystal methamphetamine and heroin produced a more desirable intoxication effect than using either substance on its own and; (4) that crystal methamphetamine provided a substitute ‘high’ for heroin after commencing OST treatment.

Conclusions: Co-use of methamphetamine and opioids has been used by people who inject drugs to facilitate intoxication, sometimes as the result of ineffective opioid substitution therapy (OST) treatment and perceived lack of pleasure after stabilisation on OST treatment.