Overall, Direct, Spillover, and Composite Effects of Components of a Peer-Driven Intervention Package on Injection Risk Behavior Among People Who Inject Drugs in the HPTN 037 Study

We sought to disentangle effects of the components of a peer-education intervention on self-reported injection risk behaviors among people who inject drugs (n = 560) in Philadelphia, US. We examined 226 egocentric groups/networks randomized to receive (or not) the intervention. Peer-education training consisted of two components delivered to the intervention network index individual only: (1) an initial training and (2) "booster" training sessions during 6- and 12-month follow up visits. In this secondary data analysis, using inverse-probability-weighted log-binomial mixed effects models, we estimated the effects of the components of the network-level peer-education intervention upon subsequent risk behaviors. This included contrasting outcome rates if a participant is a network member [non-index] under the network exposure versus under the network control condition (i.e., spillover effects). We found that compared to control networks, among intervention networks, the overall rates of injection risk behaviors were lower in both those recently exposed (i.e., at the prior visit) to a booster (rate ratio [95% confidence interval]: 0.61 [0.46-0.82]) and those not recently exposed to it (0.81 [0.67-0.98]). Only the boosters had statistically significant spillover effects (e.g., 0.59 [0.41-0.86] for recent exposure). Thus, both intervention components reduced injection risk behaviors with evidence of spillover effects for the boosters. Spillover should be assessed for an intervention that has an observable behavioral measure. Efforts to fully understand the impact of peer education should include routine evaluation of spillover effects. To maximize impact, boosters can be provided along with strategies to recruit especially committed peer educators and to increase attendance at trainings. Clinical Trials Registration Clinicaltrials.gov NCT00038688 June 5, 2002.

Prevalence and correlates of prescription opioid residue injection

BACKGROUND

There is growing evidence of intravenous administration of prescription opioids (POs) in several countries. Preparation of POs for injection may leave residues in containers and filters used by people who inject drugs and may lead to adverse health outcomes if they are injected.

METHODS

This exploratory study used cross-sectional data from the COSMO study, a prospective cohort of out-of-treatment cocaine users carried out in Montréal (Canada) between October 2010 and August 2015. For this analysis, only one visit per participant was selected, that is, the first time the participant reported PO injection during the study. The outcome of interest, "injection of PO residues", was defined as having injected PO residues from a filter and/or a container in the last month. Correlates of this outcome were identified using logistic regression analyses.

RESULTS

Of the 122 participants who reported PO injection during the study period, 41.8% had injected PO residues. Reporting an unstable source of income (AOR=4.26; 95% CI: 1.03-17.69), a recent overdose (AOR=5.45; 95% CI: 1.50-19.88) and a preponderant use of opiates (mostly opiate use versus other drugs excluding alcohol and cannabis) (AOR=2.46; 95% CI: 1.08-5.63) increased the risk of PO residue injection. The odds of reporting PO residue injection rose by 7% per unit increase in the score of psychological distress (AOR=1.07 per unit increase; 95% CI: 1.01-1.12).

CONCLUSIONS

The findings of this study suggest that PO residue injection is associated with markers of vulnerability. Further investigation is needed in order to better understand this understudied drug injection practice.