# Characterizing patterns of opioid and stimulant use by route and associations with non-fatal overdose and xylazine use in people who have injected drugs from Baltimore, MD, 2023–2024

## TL;DR

The study finds that people who inject both opioids and stimulants in Baltimore are at higher risk of non-fatal overdose and xylazine use.

## Contribution

It identifies injection of both drug types as a key risk factor during the fourth wave of the overdose epidemic.

## Key findings

- Over half of participants used both opioids and stimulants in the past six months.
- Injecting both drugs was associated with a 22.3% higher risk of non-fatal overdose.
- Xylazine use was predominantly reported among those using both opioids and stimulants.

## Abstract

The fourth wave of the overdose epidemic in the United States (US) is characterized by deaths involving fentanyl with stimulants. Understanding patterns of substance use as novel drugs continue to emerge is critical to inform overdose prevention. Among people with a history of injection drug use in Baltimore, MD, we examined opioid-stimulant use by route and the association of injection with non-fatal overdose and xylazine use.

We included 1132 participants in the AIDS Linked to the IntraVenous Experience cohort with a study visit in 2023–2024. We characterized participants by self-reported past-six-month use of any opioid and any stimulant by route using descriptive statistics. Adjusted associations were estimated using targeted minimum loss-based estimation.

Most participants were Black (68 %), male (67 %), and older (median: 56 years). 53 % reported using both opioids and stimulants; these participants were more likely to report using other substances, non-fatal overdose, depressive symptoms, and homelessness. Among participants using both, those injecting both were more likely to report non-fatal overdose and xylazine use than those using by non-injection (overdose: PD = 22.3 %, 95 % CI= 17.2 %-27.5 %; xylazine: PD = 13.3 %, 95 % CI = 4.7 %-21.9 %).

We provide one of the most comprehensive summaries of substance use during the fourth wave in Baltimore, a city with the highest rate of fatal overdose in the US during the study period. Use of multiple substances was common, and many participants reported injection. Overdose prevention should be targeted to those injecting both drugs as this pattern had heightened overdose risk.

•Over half of sample reported using both opioids and stimulants in past 6 months.•Use of both related to use of other drugs, social disadvantage, and depression.•Xylazine use found predominantly in participants reporting use of both.•Among those reporting both, injecting both associated with non-fatal overdose.

Over half of sample reported using both opioids and stimulants in past 6 months.

Use of both related to use of other drugs, social disadvantage, and depression.

Xylazine use found predominantly in participants reporting use of both.

Among those reporting both, injecting both associated with non-fatal overdose.