Latent patterns of polysubstance use among people who use opioids: A systematic review

Prevalence and factors associated with polydrug use among clients seeking treatment for alcohol misuse

INTRODUCTION

The aim of this paper was to examine the client and psychosocial characteristics associated with polydrug use in patients with alcohol misuse as their primary drug of concern (PDC) seeking treatment from substance use treatment centres.

METHODS

Self-report surveys were undertaken with clients attending 1 of 34 community-based substance use treatment centres across Australia with alcohol as their PDC. Survey items included client's socio-demographic characteristics, level of alcohol dependence, use of other drugs including tobacco, health and wellbeing factors including health-related quality of life. The factors associated with polydrug use (alcohol use concurrent with at least one other drug) were examined.

RESULTS

In a sample of 1130 clients seeking treatment primarily for alcohol problems, 71% reported also using another drug. The most frequently used drug was tobacco (50%) followed by cannabis (21%) and benzodiazepines (15%). Excluding tobacco use, 35% of participants reported polydrug use. Factors associated with any polydrug use were younger age, lower education levels, lower levels of mental health related quality of life and housing risk (i.e., risk of eviction or experienced homelessness in past 4 weeks). When tobacco was excluded, factors associated with polydrug use were age, lower physical and mental health-related quality of life, and housing risk.

DISCUSSION AND CONCLUSIONS

Most adults seeking treatment for alcohol misuse as their PDC reported using another drug in addition to alcohol. Treatment services should be designed accordingly to maximise the likelihood of treatment engagement and success.

Relationship between opioid cross-tolerance during buprenorphine stabilization and return to opioid use during buprenorphine dose tapering

RATIONALE

Opioid injection drug use (IDU) has been linked to a more severe pattern of use (e.g. tolerance, overdose risk) and shorter retention in treatment, which may undermine abstinence attempts.

OBJECTIVES

This secondary data analysis of four human laboratory studies investigated whether current opioid IDU modulates subjective abuse liability responses to high-dose hydromorphone during intermediate-dose buprenorphine stabilization (designed to suppress withdrawal but allow surmountable agonist effects), and whether hydromorphone response magnitude predicts latency of return to opioid use during buprenorphine dose-tapering.

METHODS

Regular heroin users not currently seeking treatment (n = 54; 29 current injectors, 25 non-injectors) were stabilized on 8-mg/day sublingual buprenorphine and assessed for subjective responses (e.g. 'liking', craving) to hydromorphone 24-mg intramuscular challenge (administered 16-hr post-buprenorphine) under randomized, double-blinded, controlled conditions. A subgroup (n = 35) subsequently completed a standardized 3-week outpatient buprenorphine dose-taper, paired with opioid-abstinent contingent reinforcement, and were assessed for return to opioid use based on thrice-weekly urinalysis and self-report.

RESULTS

During buprenorphine stabilization, IDU reported lower 'liking' of buprenorphine and post-hydromorphone peak 'liking', 'good effect' and 'high' compared to non-IDU. Less hydromorphone peak increase-from-baseline in 'liking' (which correlated with less hydromorphone-induced craving suppression) predicted significantly faster return to opioid use during buprenorphine dose-tapering.

CONCLUSIONS

In these buprenorphine-stabilized regular heroin users, IDU is associated with attenuated 'liking' response (more cross-tolerance) to buprenorphine and to high-dose hydromorphone challenge and, in turn, this cross-tolerance (but not IDU) predicts faster return to opioid use. Further research should examine mechanisms that link cross-tolerance to treatment response.

Longitudinal patterns of use of stimulants and opioids in the AIDS linked to the IntraVenous experience cohort, 2005-2019

BACKGROUND

Overdoses involving opioids and stimulants are on the rise, yet few studies have examined longitudinal trends in use of both substances. We sought to describe use and co-use of opioids and stimulants, 2005-2019, in the AIDS Linked to the Intravenous Experience (ALIVE) cohort - a community-based cohort of people with a history of injection drug use living in or near Baltimore, MD.

METHODS

We included 2083 ALIVE participants, who had at least two visits during the study period. Our outcome was based on self-reported use of opioids and stimulants in the prior 6 months. We estimated prevalence of 4 categories of use (neither stimulants nor opioids, only stimulants, only opioids, stimulants and opioids), using a non-parametric multi-state model, accounting for the competing event of death and weighting for informative loss to follow-up. All analyses were stratified by enrollment cohort, with the main analysis including participants who enrolled prior to 2015 and a sub-analysis including participants who enrolled 2015-2018.

RESULTS

In the main analysis, prevalence of using stimulants and opioids decreased from 38 % in 2005 to 12 % 2013 but stabilized from 2014 onwards (13-19 %). The prevalence of using only stimulants (7-11 %) and only opioids (5-10 %) was stable across time. Participants who reported using both were more likely to report homelessness, depression, and other substance use (e.g., marijuana and heavy alcohol use) than participants in the other use categories. On average, 65 % of visits with use of both were followed by a subsequent visit with use of both; of participants transitioning out of using both, 13% transitioned to using neither.

CONCLUSIONS

While use of stimulants and opioids declined in the cohort through 2013, a meaningful proportion of participants persistently used both. More research is needed to understand and develop strategies to mitigate harms associated with persistent use of both stimulants and opioids.

Correlates of Stimulant Use among People Who Use Heroin Undergoing Treatment in Out-Patient Facilities in France, 2010-2020

Background: Polydrug use has been implicated in driving a "fourth wave" of the overdose crisis in North America, specifically through concurrent use of stimulants and opioids, especially fentanyl. In France, however, heroin has historically been and remains the easiest-to-access opioid, accounting for most drug treatment demand. Whether similar polydrug use is increasing in Western Europe remains understudied, despite severe health implications and potential inadequate public health responses.Methods: We take advantage of a nation-wide dataset containing information on all patients serviced in treatment centers in France from 2010 to 2020. We conduct Poisson regression to determine the main predictors of stimulant use among people who use heroin (PWUH) and opioids (PWUO) generally.Results: Heroin remains the primary opioid within drug treatment in France. A decreasing number of out-patients seeking treatment for heroin use has been accompanied by an increasing trend of stimulant use over time, most commonly with powder cocaine. Our results suggest a significant increase of crack cocaine use among the most vulnerable PWUH. Concurrent use of stimulants among PWUH was positively associated with use of alcohol, cannabis, unprescribed psychotropics and hallucinogens, and negatively with tobacco. Similar results were found for all in-treatment PWUO.Conclusions: Our results uncover heterogeneity in the profiles of PWUH that should be fully acknowledged to ensure better efficiency in substance use clinical practices and policy, while simultaneously drawing attention to trends in concurrent opioid-stimulant use outside North America. We advocate for an extension of the generalized risk framework and its implementation in prevention programs.

Longitudinal polysubstance use patterns and non-fatal overdose: A repeated measures latent class analysis

BACKGROUND

Polysubstance use (PSU) is common among people who use opioids (PWUO) and has been associated with drug-related harms. We aimed to identify latent longitudinal PSU classes among a cohort of PWUO and characterize non-fatal overdose risks among different sub-classes over time.

METHODS

We used longitudinal data (2005-2018) from three ongoing prospective cohorts of people who use drugs in Vancouver, Canada. The primary outcome of interest was self-reported non-fatal overdose during the past six months. The primary exposure of interest was longitudinal PSU patterns among PWUO, obtained from repeated measures latent class analysis (RMLCA) of weekly substance use-related outcome indicators. Multivariable generalized estimating equations models were built to assess the association between latent PSU class membership and non-fatal overdose, adjusting for potential sociodemographic, behavioural, and structural confounders.

RESULTS

2627 PWUO were included in the analysis, and 1094 (41.6 %) had experienced at least one non-fatal overdose during the study period. RMLCA revealed five distinct latent longitudinal PSU classes, including low/infrequent use (Class 1; 30 %), primarily opioid and methamphetamine use (Class 2; 22 %), primarily cannabis use (Class 3; 15 %), primarily opioid and crack use (Class 4; 29 %), and frequent PSU (Class 5; 4 %). In comparison with Class 1 (low), membership in all latent PSU classes except Class 3 (cannabis) was associated with increased odds of non-fatal overdose: Class 2 (opioids + meth) vs. Class 1 (Adjusted odds ratios [aOR] = 2.20, 95 % confidence intervals [CI]: 1.51-3.22), Class 4 (opioids + crack) vs. Class 1 (aOR = 1.06, 95 % CI: 0.85-1.33), and Class 5 (frequent) vs. Class 1 (aOR = 2.39, 95 % CI: 1.92-2.97).

CONCLUSION

Our findings highlighted the heterogeneous characteristics of PWUO in terms of patterns of PSU and non-fatal overdose risk. The diverse nature of PWUO and the potential additive or multiplicative impact of using several substances on overdoses should be reflected across the substance use treatment continuum and care provision.

Are you thinking what I'm thinking? Defining what we mean by "polysubstance use."

The rise in drug overdoses and harms associated with the use of more than one substance has led to increased use of the term "polysubstance use" among researchers, clinicians, and public health officials. However, the term retains no consistent definition across contexts. The current authors convened from disciplines including sociology, epidemiology, neuroscience, and addiction psychiatry to propose a recommended definition of polysubstance use. An iterative process considered authors' formal and informal conversations, insights from relevant symposia, talks, and conferences, as well as their own research and clinical experiences to propose the current definition. Three key concepts were identified as necessary to define polysubstance use: (1) substances involved, (2) timing, and (3) intent. Substances involved include clarifying either (1) the number and type of substances used, (2) presence of more than one substance use disorder, or (3) primary and secondary substance use. The concept of timing is recommended to use clear terms such as simultaneous, sequential, and same-day polysubstance use to describe short-term behaviors (e.g., 30-day windows). Finally, the concept of intent refers to clarifying unintentional use or exposure when possible, and greater attention to motivations of polysubstance use. These three components should be clearly defined in research on polysubstance use to improve consistency across disciplines. Consistent definitions of polysubstance use can aid in the synthesis of evidence to better address an overdose crisis that increasingly involves multiple substances.

The impact of polysubstance use patterns on engagement of substance use disorder treatment among emergency department patients at high risk of opioid overdose

Background

Substance use patterns are diverse, and multiple substances are often involved in fatal and nonfatal overdoses. Additionally, polysubstance use is associated with greater difficulty accessing and remaining in substance use disorder (SUD) treatment. The aim of this study was to identify substance use patterns and determine their association with SUD treatment engagement among emergency department (ED) patients at risk of opioid overdose.

Methods

This was a sub-analysis of a randomized controlled trial comparing two behavioral interventions for individuals at two EDs in Rhode Island from 2018 to 2021. Past six-month substance use frequency for eight substances plus injection drug use was self-reported at trial enrollment, and SUD treatment engagement within 90 days after enrollment was obtained using administrative data linkages. Latent class analysis identified substance use patterns and multivariable log-binomial models estimated the association with SUD treatment engagement.

Results

Among 607 participants, there were four substance use patterns: 1) low reported use (n = 295), 2) frequent injection and heroin use (n = 131), 3) high frequency broad polysubstance use (n = 62), and 4) low frequency broad polysubstance use (n = 119). Compared to participants with the low reported use pattern, those with the frequent injection and heroin pattern had a greater likelihood of SUD treatment engagement (adjusted risk ratio = 1.28; 95% confidence interval = 1.02-1.61).

Conclusions

Distinct and meaningful polysubstance use patterns showed differential SUD treatment engagement after ED discharge. Nuanced relationships between substance use patterns and treatment highlight the necessity for tailored harm reduction, treatment, and recovery services.

Trends in deaths following drug use in England before, during, and after the COVID-19 lockdowns

Aim

This research aimed to describe how the characteristics of deaths following drug use changed during the COVID-19 pandemic in England, and how this can inform future strategy to support the health and social care of people who use drugs in future emergency scenarios.

Method

All deaths reported to the National Programme on Substance Abuse Deaths which occurred between January 2018 and December 2021 inclusive were extracted for analysis. Exponential smoothing models were constructed to determine any differences between forecasted vs. actual trends.

Key results

Following the first lockdown period in England there were significant increases in the proportion of people who died at home beyond the 95% confidence bounds of the exponential smoothing model and concurrent decreases in the proportion of people who died in hospital. Whilst the overall proportion of deaths attributable to opioids did not significantly deviate from the forecasted trend, there were significant increases in methadone-related deaths and decreases in heroin/morphine-related death beyond the 95% confidence bounds. The proportion of deaths concluded as suicide increased, as did those implicating antidepressant use. There were no changes in the proportion of deaths following use of other drug classes, alcohol use in combination with psychoactive drugs, or on decedent demographics (gender, age, and drug user status). A small number of deaths due to drug use had COVID-19 infection itself listed as a cause of death (n = 23).

Conclusion

For people who use drugs, the impact of the restrictions due to the COVID-19 pandemic was greater than that of infection from the virus itself. The health and social care strategy for these people needs to be pre-emptively adapted to mitigate against the specific risk factors for fatal drug overdose associated with future emergency scenarios.

High willingness to use overdose prevention sites among suburban people who use drugs who do not inject

INTRODUCTION

Overdose prevention sites (OPS) are evidence-based interventions to improve public health, yet implementation has been limited in the USA due to a variety of legal impediments. Studies in various US settings have shown a high willingness to use OPS among urban and rural people who inject drugs, but data among people who use drugs (PWUD) via non-injection routes of administration in suburban areas are lacking.

METHODS

We utilized cross-sectional data from a sample of suburban PWUD who have not injected drugs in the past 3 months (N = 126) in Anne Arundel County, Maryland. We assessed PWUDs' likelihood of using a hypothetical OPS and perceived potential barriers to accessing OPS. We tested for associations between sociodemographic characteristics, drug use, service access, and overdose experiences with willingness to utilize OPS.

FINDINGS

Participants' median age was 42, and the majority were men (67%) and non-Hispanic Black (79%). Sixty-six percent reported willingness to use an OPS. Concerns about confidentiality (29%), arrest (20%), and transportation costs (22%) were the most anticipated barriers to using OPS. Men (75% vs 55%, p = 0.015), participants who used heroin (53% vs 32%, p = 0.017), and participants who used multiple overdose prevention behaviors (e.g., using fentanyl test strips) (36% vs 19%, p = 0.006) were more likely to report willingness to use OPS.

CONCLUSION

Most suburban non-injecting PWUD in the sample were willing to use an OPS. OPS implementation strategies in suburban settings should be tailored to reach PWUD via non-injection routes of administration while meeting the unique needs of suburban contexts.

Differing Behaviors Around Adult Nonmedical Use of Prescription Stimulants and Opioids: Latent Class Analysis

BACKGROUND

The availability of central nervous system stimulants has risen in recent years, along with increased dispensing of stimulants for treatment of, for example, parent-reported attention-deficit/hyperactivity disorder in children and new diagnoses during adulthood. Typologies of drug use, as has been done with opioids, fail to include a sufficient range of behavioral factors to contextualize person-centric circumstances surrounding drug use. Understanding these patterns across drug classes would bring public health and regulatory practices toward precision public health.

OBJECTIVE

The objective of this study was to quantitatively delineate the unique behavioral profiles of adults who currently nonmedically use stimulants and opioids using a latent class analysis and to contrast the differences in findings by class. We further evaluated whether the subgroups identified were associated with an increased Drug Abuse Screening Test-10 (DAST-10) score, which is an indicator of average problematic drug use.

METHODS

This study used a national cross-sectional web-based survey, using 3 survey launches from 2019 to 2020 (before the COVID-19 pandemic). Data from adults who reported nonmedical use of prescription stimulants (n=2083) or prescription opioids (n=6127) in the last 12 months were analyzed. A weighted latent class analysis was used to identify the patterns of use. Drug types, motivations, and behaviors were factors in the model, which characterized unique classes of behavior.

RESULTS

Five stimulant nonmedical use classes were identified: amphetamine self-medication, network-sourced stimulant for alertness, nonamphetamine performance use, recreational use, and nondiscriminatory behaviors. The drug used nonmedically, acquisition through a friend or family member, and use to get high were strong differentiators among the stimulant classes. The latter 4 classes had significantly higher DAST-10 scores than amphetamine self-medication (P<.001). In addition, 4 opioid nonmedical use classes were identified: moderate pain with low mental health burden, high pain with higher mental health burden, risky behaviors with diverse motivations, and nondiscriminatory behaviors. There was a progressive and significant increase in DAST-10 scores across classes (P<.001). The potency of the opioid, pain history, the routes of administration, and psychoactive effect behaviors were strong differentiators among the opioid classes.

CONCLUSIONS

A more precise understanding of how behaviors tend to co-occur would improve efficacy and efficiency in developing interventions and supporting the overall health of those who use drugs, and it would improve communication with, and connection to, those at risk for severe drug outcomes.

Longitudinal latent polysubstance use patterns among a cohort of people who use opioids in Vancouver, Canada

INTRODUCTION

Polysubstance use (PSU) practices are increasing among people who use opioids (PWUO). However, several aspects of longitudinal PSU patterns among PWUO remain understudied. This study aims to identify person-centred longitudinal patterns of PSU among a cohort of PWUO.

METHODS

Using longitudinal data (2005-2018) from three prospective cohort studies including people who use drugs in Vancouver, Canada, we used repeated measures latent class analysis to identify different PSU classes among PWUO. Multivariable generalised estimating equations models weighted by the respective posterior membership probabilities were applied to identify covariates of membership in different PSU classes over time.

RESULTS

Overall, 2627 PWUO (median age at baseline: 36 [quartile 1-3: 25-45]) were included between 2005 and 2018. We found five distinct PSU patterns, including low/infrequent probability of regular substance use (Class 1; 30%), primarily opioid and methamphetamine use (Class 2; 22%), primarily cannabis use (Class 3; 15%), primarily opioid and crack use (Class 4; 29%) and frequent PSU (Class 5; 4%). Membership in Class 2, 4 and 5 was positively associated with several behavioural and socio-structural adversities.

DISCUSSION AND CONCLUSIONS

Findings of this longitudinal study suggest PSU is the norm among PWUO and highlights the heterogeneous characteristics of PWUO. The diversities within the population of PWUO need to be recognised in addiction care and treatment as well as optimising resource allocation in the response to the overdose crisis.

Latent polydrug use patterns and the provision of injection initiation assistance among people who inject drugs in three North American settings

INTRODUCTION

We sought to identify latent profiles of polysubstance use patterns among people who inject drugs in three distinct North American settings, and then determine whether profile membership was associated with providing injection initiation assistance to injection-naïve persons.

METHODS

Cross-sectional data from three linked cohorts in Vancouver, Canada; Tijuana, Mexico; and San Diego, USA were used to conduct separate latent profile analyses based on recent (i.e., past 6 months) injection and non-injection drug use frequency. We then assessed the association between polysubstance use patterns and recent injection initiation assistance provision using logistic regression analyses.

RESULTS

A 6-class model for Vancouver participants, a 4-class model for Tijuana participants and a 4-class model for San Diego participants were selected based on statistical indices of fit and interpretability. In all settings, at least one profile included high-frequency polysubstance use of crystal methamphetamine and heroin. In Vancouver, several profiles were associated with a greater likelihood of providing recent injection initiation assistance compared to the referent profile (low-frequency use of all drugs) in unadjusted and adjusted analyses, however, the inclusion of latent profile membership in the multivariable model did not significantly improve model fit.

DISCUSSION AND CONCLUSIONS

We identified commonalities and differences in polysubstance use patterns among people who inject drugs in three settings disproportionately impacted by injection drug use. Our results also suggest that other factors may be of greater priority when tailoring interventions to reduce the incidence of injection initiation. These findings can aid in efforts to identify and support specific higher-risk subpopulations of people who inject drugs.

Trends and psychosocial correlates of same day polysubstance use among people who inject drugs in Australia, 2012-2022

BACKGROUND

Polysubstance use is associated with negative health and social outcomes among people who inject drugs. We aimed to describe trends in polysubstance use and identify psychosocial correlates and associated drug use risk behaviours. We defined polysubstance use as intentional same day use of more than one of three drug classes: opioids, other non-opioid depressants (hereafter 'depressants'), and stimulants.

METHODS

We used 10 years (2012-2022, excluding 2020) of data from annual surveys in Australian capital cities with people who inject drugs (N=5657) to construct five mutually exclusive polysubstance use profiles: opioid-depressant, opioid-stimulant, stimulant-depressant, opioid-stimulant-depressant, and single drug class use. We examined time trends using the Mann Kendall test and identified correlates using multinomial logistic regression.

RESULTS

Same day polysubstance use was relatively common among this sample (43.6%). Opioid-depressant use was the most frequent polysubstance use profile, but this decreased over the study period (32.6% to 13.3%, p<0.001). This aligned with observed decreases in use of pharmaceutical opioids (p<0.001), opioid agonist treatment (p=0.007), and benzodiazepines (p=0.001). There was no evidence for any trend in the other polysubstance use profiles, although single drug class use increased (51.9% to 64.7%, p=0.031). The different polysubstance use profiles were variously associated with psychosocial factors, including unstable housing and very high psychological distress, and other drug use risk behaviours, including non-fatal overdose, receptive and/or distributive needle sharing, and reusing one's own needles.

CONCLUSION

Same day polysubstance use has remained relatively common among this sample over time, although the typology has changed. Collectively, our findings point to diverse drug use patterns among people who inject drugs and reiterate the need for a range of harm reduction, treatment, and support options.

Factors Associated with HIV Testing Among People Who Inject Drugs: Findings from a Multistate Study at the Start of the COVID-19 Pandemic

Few studies have examined HIV testing among people who inject drugs (PWID) during the COVID-19 pandemic. This study examines factors associated with PWID who have been recently (past six months) tested for HIV during the COVID-19 pandemic. PWID were recruited between August 2020 and January 2021 from 22 drug treatment and harm reduction programs in nine states and the District of Columbia. We used logistic regression to identify correlates of recent HIV testing among PWID (n = 289). Most (52.9%) PWID reported having been recently tested for HIV. Factors associated with recent HIV testing included: having attended college [adjusted odds ratio (aOR) 2.32, 95% confidence interval (95% CI) 1.32-4.10], weekly hunger (aOR 2.08, 95% CI 1.20-3.60), crystal methamphetamine injection (aOR 2.04, 95% CI 1.05-3.97), and non-metropolitan residence (aOR 0.33, 95% CI 0.13, 0.88). Findings suggest HIV testing initiatives should be expanded during times of crisis, such as global pandemics.

Predictors and motives of polydrug use in opioid users. A narrative review

PURPOSE OF REVIEW

To review the recent literature on predictors and personal motives of polydrug use in opioid users with a focus on combined use of opioids with stimulants, benzodiazepines and gabapentinoids.

RECENT FINDINGS

In North America, methamphetamine is now the most prevalent co-drug in opioid users and is responsible for high mortality rates. In Europe, opioids are rather combined with either cocaine, benzodiazepines or gabapentionoids, but recent data are lacking.Main personal motives of opioid users to combine opioids with methamphetamine or cocaine is to boost the opioid high, inhibit the withdrawal effects of heroin and have a cheaper alternative to maintain the opioid high. Risk factors of polydrug use by opioid users included being male, younger age, homelessness, high-risk sexual behavior, needle sharing, incarceration, poor mental health and recent use of cocaine or prescription opioids. The motives for co-use of opioids and gabapentinoids also include seeking a better high, lower price and to self-medicate pain/physical symptoms, including those resulting from withdrawal.

SUMMARY

When treating opioid users with polydrug drug use, special attention should be paid to dosing when in opioid agonist methadone/buprenorphine treatment and to the presence of physical pain. The validity of part of the personal motives seems questionable which deserves attention when counselling opioid users with polydrug use.

Patterns and contexts of polysubstance use among young and older adults who are involved in the criminal legal system and use opioids: A mixed methods study

INTRODUCTION

Opioid prevention and treatment programs tailored to young adults involved in the criminal legal system are rare. We examined profiles of polysubstance use among younger and older adults involved in the criminal legal system who use opioids, and explored their experiences and motivations related to substance use. Information gleaned can inform the adaptation of existing programs and the development of novel approaches for young adults in the criminal legal system.

METHODS

Using a sequential mixed methods design we 1) quantitatively identified typologies of polysubstance users among adults aged 18-24 (n = 92) and those age 25 and over (n = 27) involved in the criminal legal system who use opioids, using latent class analysis and 2) qualitatively explored differences in personal motivations, cultural influences, and psychosocial contexts of substance use by class.

RESULTS

Our quantitative results supported a three-class typology: the majority of participants were in Class I (73 %, n = 87) and reported using primarily alcohol and marijuana. Participants in Classes II (15 %, n = 18) and III (12 %, n = 14) endorsed distinct and complicated polysubstance use profiles. Further, participants in Classes I and III were significantly younger than those in Class II. Qualitative analysis allowed us to understand associations between patterns of use, motivations, and contexts among young and older adults, comparing across classes.

CONCLUSIONS

Our results highlight the importance of attending to the needs of subpopulations based on age and use patterns to adapt and develop targeted treatment and prevention programs for high-risk adults involved in the criminal legal system.

Shifts in substance use patterns among a cohort of people who use opioids after delisting of OxyContin in BC, Canada: An interrupted time series study

BACKGROUND

OxyContin was delisted from Canadian provincial drug formularies in March 2012 and replaced with a reformulated tamper-resistant form of oxycodone (i.e., OxyNeo). We assessed if delisting of OxyContin was associated with changes in the use of unregulated opioids and other substances among people who use opioids (PWUO).

METHODS

Data were derived from two prospective cohort studies of people who use drugs in Vancouver, BC, Canada from 2006 to 2018. PWUO who had at least one follow-up visit before and after delisting of OxyContin were included. Outcomes of interest were self-reported regular (i.e., at least weekly) use of heroin, non-prescribed prescription opioids, cannabis, methamphetamine, crack cocaine, and powder cocaine during the previous six months. Using quasi-experimental interrupted time series, we fit generalized least squares models to assess participants' immediate and long-term substance use practices after the policy change.

RESULTS

We analyzed data from 1014 participants who contributed to 17457 visits during the study. Following the delisting of OxyContin, heroin use increased immediately by 5.17% (95% confidence intervals [CI]: 0.68 to 9.67) and over time by 0.47% (0.35 to 0.58) per month. Non-prescribed prescription opioid use increased immediately by 1.80% (0.10 to 3.50) and over time by 0.16% (0.12 to 0.19) per month. Cannabis use increased immediately by 4.37% (0.88 to 7.87) and over time by 0.11% (0.02 to 0.19) per month. Methamphetamine use did not increase immediately but increased over time by 0.10% (0.01 to 0.18) per month. Crack cocaine use decreased immediately by 6.13% (-10.94 to -1.69) but not significantly over time. Lastly, powder cocaine use did not increase immediately or over time.

CONCLUSIONS

Delisting of OxyContin in BC was not associated with a reduction in unregulated opioid use among PWUO. Our findings point to a shift in substance use patterns of PWUO post-intervention and further highlight the unintended consequences of supply-reduction interventions in addressing the opioid epidemic.

Latent Classes of Polysubstance Use and Associations with HIV Risk and Structural Vulnerabilities among Cisgender Women Who Engage in Street-Based Transactional Sex in Baltimore City

We describe patterns of polysubstance use and associations with HIV risk-related behaviors among women engaged in street-based transactional sex, an understudied yet important population and area of research. This sample was restricted to cisgender women who reported drug use (n = 244) in the baseline of the longitudinal SAPPHIRE cohort study. Latent class analysis (LCA) was conducted using drug use measures (route of administration (injection/non-injection); type of drug (specific opioids, stimulants)) and selection based on fit statistics and qualitative interpretation of the classes. Polysubstance use was prevalent (89% ≥ 2), and 68% had injected drugs in the past 3 months. A three-class solution was selected: Class 1 ("heroin/cocaine use", 48.4% of sample), Class 2 ("poly-opioid use", 21.3%), and Class 3 ("poly-route, polysubstance use", 30.3%). Class 3 was significantly younger, and Class 2 was disproportionately non-White. Women reported high levels of housing (63%) and food (55%) insecurity, condomless sex with clients (40%), and client-perpetrated violence (35%), with no significant differences by class. Obtaining syringes from syringe services programs differed significantly by class, despite injection behaviors in all classes. Tailored HIV and overdose prevention programming that considers drug use patterns would strengthen their impact.