Heroin injection to fentanyl smoking: Examining temporal trends in substance type and route of administration among people who inject drugs in Los Angeles, CA and Denver, CO, USA between 2021–2022

Abstract

Introduction

In the US, fentanyl is replacing heroin in illicit drug markets. We examined temporal effects of changing substance use patterns and self-reported skin abscesses among people who inject drugs (PWID).

Methods

We surveyed 472 PWID in Los Angeles, CA and Denver, CO during 2021/22. Survey items covered demographics, drug use patterns (type, frequency, and route of administration), injection-related risk behaviors, and self-reported skin abscesses over the last 3 months.

Analysis

We used baseline data to determine if heroin and fentanyl use patterns and health outcomes changed over time. We reclassified the sample into three – 6-month participant recruitment periods (Period 1: Apr to Sep 2021 [n = 256/54 %]; Period 2: Oct to Mar 2021/22 [n = 129/27 %]; Period 3: Apr to Sep 2022[n = 87/18 %]). We used bivariable analyses to determine factors associated with daily injection of any drug, daily non-injection fentanyl use, and abscesses. Regression analyses were conducted to determine factors associated with these changing substance use patterns and abscesses.

Results

We observed statistically significant changes in the following: daily injection (78 % in Period 1 to 56 % in Period 3; p < 0.001), daily heroin use (46 % in P1 to 28 % in P3;), daily fentanyl smoking (18 % in Period 1 to 33 % in Period 3) and abscesses (43 % in P1 to 32 % in). In multivariable robust Poisson regression models, participants recruited in later periods with lower risk of daily injection and abscesses and higher risk of daily non-injection fentanyl use.

Discussion

Changes in the illicit opioid market have resulted in decreased injection and increased non-injection fentanyl use. Lower injection drug use may be leading to lower risk for abscesses among PWID.