Patterns of polysubstance use and overdose among people who inject drugs in Baltimore, Maryland: A latent class analysis

Background: Opioid-related overdose rates continue to climb. However, little research has examined the reach of overdose education and naloxone trainings among people who inject drugs (PWID). Understanding gaps in coverage is essential to improving the public health response to the ongoing crisis. Methods: We surveyed 298 PWID in Baltimore City, MD. We conducted a latent class analysis of drug use indicators and tested for differences by class in past month overdose, having received overdose training, and currently having naloxone. Results: Three classes emerged: cocaine/heroin injection (40.2%), heroin only injection (32.2%), and multi-drug/multi-route use (27,6%). The prevalence of past month overdose differed marginally by class (p = 0.06), with the multi-drug/multi-route use class having the highest prevalence (22.5%) and the heroin only class having the lowest (4.6%). The prevalence of previous overdose training differed significantly by class (p = 0.02), with the heroin/cocaine class (76.5%) having more training than the other two classes. Training was least common amongst the multi-drug/multi-route class (60.3%), though not statistically different from the heroin only class (63.0%). Classes did not differ significantly in current naloxone possession, although the multi-drug/multi-route class exhibited the lowest prevalence of naloxone possession (37.2%). Conclusions: People who inject multiple substances are at high risk for overdose and are also the least likely to receive overdose trainings. The current service landscape does not adequately reach individuals with high levels of structural vulnerability and high levels of drug use and homelessness. Actively including this subgroup into harm reduction efforts are essential for preventing overdose fatalities.