People who inject drugs are transitioning to smoking them

Researchers from the University of California San Diego have revealed new trends in drug consumption that shed light on how people are adapting to the evolving risks associated with unregulated drug use in the United States. The findings could help policymakers and public health officials better tailor interventions to meet the needs of vulnerable populations and reduce the public health burden of substance-related harm.

The study was published in Drug and Alcohol Dependence.

Since the early 2010s, deaths from accidental overdoses have been on the rise in the United States due to an increase in the contamination of unregulated drugs, particularly injected drugs, with fentanyl, an opioid that is 50 times more potent than heroin and 100 times more potent than morphine. People who inject drugs are also at a substantially higher risk, than other communities, for blood-borne diseases such as HIV and Hepatitis C through sharing needles or other injection supplies.

The researchers found that among a cohort of 362 people in the San Diego area who had previously injected opioids or methamphetamine, the proportion of individuals solely smoking these drugs increased from 0% to 34% between 2020 and 2023. There was also a significant overall decline in the injection of both types of drugs, suggesting an emerging trend towards smoking these substances as opposed to injecting them.

Although researchers in San Francisco had previously documented transitions from injecting heroin to smoking fentanyl, the new San Diego study found that high proportions of people who injected heroin, methamphetamine or fentanyl reported transitioning to smoking.

Study participants were from the La Frontera cohort study, an ongoing investigation of HIV, Hepatitis C and drug overdose outcomes in the context of binational drug markets and cross-border mobility between San Diego, United States, and Tijuana, Mexico. Because most of the unregulated opioids in the United States originate in Mexico, this region is critical to understanding the evolving drug supply and its effects on public health.

The researchers hypothesize that the emergence of fentanyl in the drug supply may have driven some individuals to switch to smoking, which could reduce the risk of HIV and viral hepatitis and other health complications associated with injection. In light of their findings, the team encouraged health departments to increase funding for and the accessibility of safer smoking supplies as part of harm reduction programs.

The study's senior author is Steffanie A. Strathdee, Associate Dean of Global Health Sciences and the Harold Simon Distinguished Professor in the Department of Medicine at UC San Diego School of Medicine. The study's first author is William Eger, a Ph.D. candidate at UC San Diego School of Medicine and San Diego State University.