Expanded brief intervention in primary care results in reduced self-reported substance use at six-month follow-up: Preliminary results

Aims: Although persons who inject drugs (PWID) in the western US–Mexico border region inject both heroin and meth, less is known about the prevalence and risks associated with simultaneous injection of this depressant-stimulant combination. Baseline data from two cohort studies of PWID conducted concurrently in San Diego and Tijuana were used to measure the prevalence and identify correlates of simultaneous injection of heroin and meth. Methods: PWID age u003e18 years who reported injecting illicit drugs in the past month were recruited using street outreach and targeted advertising in San Diego (n=574) and Tijuana (n=735). Participants completed interviewer-administered questionnaires that included socio-demographics andpast 6monthdruguse, overdose history, and engagement in HIV-associated drug and sexual risk behaviors. Bivariate andmultivariable logistic regression analyses were used to identify correlates of simultaneous heroin and meth injection. Results: The prevalence of simultaneous injection was 39.9% overall andwas higher in Tijuana (55.8%) than in San Diego (19.8%). In multivariable analyses adjusting for study site, distributive syringe sharing [AOR: 1.80], using a pre-filled syringe [AOR: 1.49], finding it hard to get new syringes [AOR: 1.51], reporting great or urgent need for treatment [AOR: 1.41], and younger age [AOR: .99] were independently associated with simultaneous injection. A significant interaction between overdose and study site showed that simultaneous injection was associated with a higher odds of past 6 month overdose in San Diego [AOR: 3.08] than in Tijuana [AOR: 1.29]. Conclusions: These findings indicate that simultaneous heroin and meth injection is more common in Tijuana than in San Diego, yet this practice had a stronger association with overdose in San Diego than in Tijuana. Simultaneous heroin andmeth injectionwas also independently associated with HIV injection risk behaviors. Financial support: T32DA023356.