Monitored, unmonitored, and solitary opioid use among overdose survivors in San Francisco and Boston

Fatal overdoses occur when people use drugs alone. Decedents may be solitary where no one was likely to find them or near others, yet unmonitored. Characterizing monitored, unmonitored, and solitary opioid use and overdose circumstances can inform overdose prevention strategies.

We conducted a secondary analysis of REBOOT 2.0 trial data (San Francisco and Boston, 2019-2023). Participants had opioid use disorder, prior overdose, and unregulated opioid use. We categorized opioid use circumstances over 120-days before study entry and up to the three most recent overdoses reported in four follow-up periods as monitored, unmonitored, or solitary. We compared monitoring when using and at overdoses by demographic and overdose characteristics using chi‑square, Kruskal-Wallis and generalized estimating equations.

During 120 days before study entry, 97% of 268 participants reported any monitored use, 81% any unmonitored use, 81% any solitary use and 68% all three at least once. Monitored use was most common for 37%, unmonitored for 31%, and solitary for 32%. A higher proportion of participants who were most commonly monitored were married or partnered, housed, and from San Francisco. Of 382 overdoses, 45% were monitored, 36% were unmonitored, and 18% were solitary. Bystanders administered naloxone in 62% of monitored, 48% of unmonitored, and 17% of solitary overdoses. A lower proportion of monitored overdoses compared to unmonitored or solitary overdoses involved emergency responders or transport.

Monitored, unmonitored, and solitary opioid use and non‑fatal overdoses were common among overdose survivors. Measuring opioid use circumstances could guide context‑specific overdose prevention (e.g., supervised consumption, safety hotlines, motionlessness detectors).