Binge drug injection among people who inject drugs in Montreal: characterizing the substances and social contexts involved to inform overdose prevention efforts

Background: High-intensity episodes of drug injection, or 'binges', may be important yet overlooked triggers of overdose and other harms among people who inject drugs (PWID). We sought to describe binge injection episodes among PWID in Montreal, Canada, and to examine social contexts of this behaviour.

Methods: Data were drawn from a longitudinal cohort study involving three-monthly interviews with active PWID. At each visit (2010-2017), participants reported whether they had injected large quantities of drugs over sustained periods until unable to continue ('binged') in the last 3 months. Bingers provided additional details about typical episodes (substances, injection frequency, persons present). Descriptive analyses were performed.

Results: 805 participants (82% male, median age 41) provided 8158 observations. A recent binge was reported during 590 visits, with 62% of bingers reporting engaging in this practice at least once a month. A range of substances were reported during binges: 21% injected heroin, 26% other opioids, 73% cocaine, 8% amphetamines. 76% reported injecting a single substance during binges: those injecting heroin reported a median 8 [Q1-Q3: 4-15] injections/episode, while those injecting other opioids reported a median 12 [Q1-Q3: 8-30] injections/episode. Cocaine and amphetamine binges both involved a median of 20 injections. Bingers reporting ≥2 substances most commonly injected cocaine with heroin or other opioids. 63% of bingers reported additional use of ≥1 non-injection drug during binges (most frequently: alcohol [45%], marijuana [44%], crack [37%]). 35% of bingers reported bingeing alone, with the remaining injecting most often with close (34%) or casual (26%) friends, romantic/sexual partners (22%) or drug consumption partners (15%).

Conclusion: Binge injection episodes involve a diverse range of substances and social contexts. Naloxone distribution efforts should aim to reach a large number of PWID, regardless of their opioid use history, to maximize population-level benefits. The high proportion of individuals bingeing alone is concerning and warrants additional outreach efforts.