Association of Illicit Fentanyl Use with Injection Risk Practices Among People who Inject Drugs.

We investigated the association between fentanyl injection frequency and sharing of injection equipment among people who inject drugs. We surveyed 249 people who inject drugs in Toronto in 2019. We estimated predicted probabilities of associations between fentanyl injection frequency and injection risk practices. In prior 6 months, 117 (47.0%) of participants injected fentanyl daily, 49 (19.7%) less than daily, and 78 (31.3%) did not inject fentanyl. Participants who injected fentanyl daily shared syringes more often than those not injecting fentanyl (25.0% vs. 4.9%; χ = 11.54, p = 0.0007). Participants who injected fentanyl daily (42.4% vs. 11.3%; χ = 18.05, p < 0.0001) and less than daily (37.2% vs. 11.3%; χ = 5.88 p = 0.02) shared cookers more often than those not injecting fentanyl. Participants who injected fentanyl daily (30.2% vs. 9.7%; χ = 9.05, p = 0.003) and less than daily (30.3% vs. 9.7%; χ = 4.11, p = 0.04) shared filters more often than those not injecting fentanyl. No differences in probabilities of sharing equipment were detected between participants who injected fentanyl daily and less than daily. People using fentanyl reported injection practices that increased risk for infectious disease transmission.