Stability or versatility: transitions in fentanyl routes of administration

Transitions in how people use drugs have long influenced drug use research and the policy landscape. In unregulated drug markets, route of administration (ROA) transitions from injecting opioids to non-injecting modes of use, sometimes called reverse transitions, are rare but have been documented historically, driven by local characteristics including social networks and drug market factors. National and local data find ROA transitions are on the rise in the US. We investigated patterns of ROA transitions, including personal and market-based motivations and perceived effects and health benefits.

We examined trends in San Francisco's drug market, including changes in substance use administration patterns and the forces motivating people who use drugs to adopt alternate or multimodal dosing strategies. We conducted 32 semi-structured qualitative interviews in 2022 using rapid assessment ethnography and observation to triangulate findings on ROA patterns and techniques among people using opioids.

We observed fluctuations in the relative availability of heroin and fentanyl which contributed to subsequent changes in ROA. Like other US locations, participants initiated fentanyl use as heroin availability diminished. Able to achieve comparable effects from fentanyl smoking relative to injection most participants indicated they had transitioned within the past several years, driven by venous access, overdose concerns and market characteristics. Transitions were graduated along a spectrum of stability, from frequent multimodal use to transitions in accord with recent patterns, notably featuring total cessation of injection. Others found combining smoking and injecting allowed greater flexibility, with smoking favored when in public, for convenience, considering sensitivity to non-injecting peers, or when seeking a milder experience enabling productivity or vigilance. Injecting was chosen for its faster effect, to avoid sharing drugs/equipment with others and especially for polysubstance combinations. A small subset of participants indicated that smoking was not a durable transition for them, necessitating a return to injection.

The stability of ROA transitions and their health impacts remain in flux amidst widespread uptake of smoking fentanyl. Smoking supply provision and harm reduction organizations are facing notable headwinds but continue to be essential for providing people control over their health and embodied and social experiences.