Patterns of cocaine and opioid co-use and polyroutes of administration among street-based cocaine users in Montréal, Canada

Impact of OPRM1 (Mu-opioid Receptor Gene) A112G Polymorphism on Dual Oxycodone and Cocaine Self-administration Behavior in a Mouse Model

The use of mu-opioid receptor (MOP-r) agonists such as oxycodone together with cocaine is prevalent, and deaths attributed to using these combinations have increased.

RATIONALE

It is unknown if functional single nucleotide polymorphisms (SNPs), such as the OPRM1 (MOP-r gene) SNP A118G, can predispose individuals to more dual opioid and psychostimulant intake. The dual self-administration (SA) of MOP-r agonists and cocaine has not been thoroughly examined, especially with regard to neurobiological changes.

OBJECTIVES

We examined oxycodone SA and subsequent dual oxycodone and cocaine SA in male and female A112G (A/G and G/G, heterozygote and homozygote, respectively) mice, models of human A118G carriers, versus wild-type (A/A) mice.

METHODS

Adult male and female A/G, G/G and A/A mice self-administered oxycodone (0.25 mg/kg/infusion, 4hr/session, FR 1.) for 10 consecutive days (sessions 1-10). Mice then self-administered cocaine (2 hr) following oxycodone SA (4 hr, as above) in each session for a further 10 consecutive days (sessions 11-20). Message RNA transcripts of 24 reward-related genes were examined in the dorsal striatum.

RESULTS

Male and female A/G and G/G mice had greater oxycodone SA than A/A mice did in the initial 10 days and in the last 10 sessions. Further, A/G and G/G mice showed greater cocaine intake than A/A mice. Dorsal striatal mRNA levels of Pdyn, Fkbp5, Oprk1, and Oprm1 were altered following oxycodone and cocaine SA.

CONCLUSIONS

These studies demonstrated that this functional genetic variation in Oprm1 affected dual opioid and cocaine SA and altered specific gene expression in the striatum.

Nicotine modifies cocaine responding in a concurrent self-administration model

BACKGROUND

Preclinical models of cocaine use disorder (CUD) have not yielded any FDA-approved pharmacotherapies, potentially due to a focus on cocaine use in isolation, which may not fully translate to real-world drug taking patterns. Cocaine and nicotine are commonly used together, and clinical research suggests that nicotine may increase the potency and reinforcing strength of cocaine. In this study, we sought to determine whether and how the addition of nicotine would alter ongoing intravenous cocaine self-administration and motivation to take cocaine in rats.

METHODS

Male Sprague-Dawley rats self-administered cocaine alone on a long access, Fixed Ratio one (FR1) schedule, and then switched to a combination of cocaine and nicotine. Finally, rats responded on a Progressive Ratio (PR) schedule for several doses of cocaine alone and in combination with a single dose of nicotine.

RESULTS

Under long access conditions, rats co-self-administering cocaine and nicotine responded less and with decreased response rates than for cocaine alone and did not escalate responding. However, under PR conditions that test motivation to take drugs, the dose response curve for the combination was shifted upwards relative to cocaine alone.

CONCLUSIONS

Together, these results suggest that nicotine may enhance the reinforcing strength of cocaine, increasing PR responding for cocaine across the dose response curve.

Polysubstance addiction patterns among 7,989 individuals with cocaine use disorder

To characterize polysubstance addiction (PSA) patterns of cocaine use disorder (CoUD), we performed a latent class analysis (LCA) in 7,989 participants with a lifetime DSM-5 diagnosis of CoUD. This analysis identified three PSA subgroups among CoUD participants (i.e., low, 17%; intermediate, 38%; high, 45%). While these subgroups varied by age, sex, and racial-ethnic distribution (p < 0.001), there was no difference with respect to education or income (p > 0.05). After accounting for sex, age, and race-ethnicity, the CoUD subgroup with high PSA had higher odds of antisocial personality disorder (OR = 21.96 vs. 6.39, difference-p = 8.08✕10-6), agoraphobia (OR = 4.58 vs. 2.05, difference-p = 7.04✕10-4), mixed bipolar episode (OR = 10.36 vs. 2.61, difference-p = 7.04✕10-4), posttraumatic stress disorder (OR = 11.54 vs. 5.86, difference-p = 2.67✕10-4), antidepressant medication use (OR = 13.49 vs. 8.02, difference-p = 1.42✕10-4), and sexually transmitted diseases (OR = 5.92 vs. 3.38, difference-p = 1.81✕10-5) than the low-PSA CoUD subgroup. These findings underscore the importance of modeling PSA severity and comorbidities when examining the clinical, molecular, and neuroimaging correlates of CoUD.

Polysubstance addiction and psychiatric, somatic comorbidities among 7,989 individuals with cocaine use disorder: a latent class analysis

Aims

We performed a latent class analysis (LCA) in a sample ascertained for addiction phenotypes to investigate cocaine use disorder (CoUD) subgroups related to polysubstance addiction (PSA) patterns and characterized their differences with respect to psychiatric and somatic comorbidities.

Design

Cross-sectional study.

Setting

United States.

Participants

Adult participants aged 18-76, 39% female, 47% African American, 36% European American with a lifetime DSM-5 diagnosis of CoUD (N=7,989) enrolled in the Yale-Penn cohort. The control group included 2,952 Yale-Penn participants who did not meet for alcohol, cannabis, cocaine, opioid, or tobacco use disorders.

Measurements

Psychiatric disorders and related traits were assessed via the Semi-structured Assessment for Drug Dependence and Alcoholism. These features included substance use disorders (SUD), family history of substance use, sociodemographic information, traumatic events, suicidal behaviors, psychopathology, and medical history. LCA was conducted using diagnoses and diagnostic criteria of alcohol, cannabis, opioid, and tobacco use disorders.

Findings

Our LCA identified three subgroups of PSA (i.e., low, 17%; intermediate, 38%; high, 45%) among 7,989 CoUD participants. While these subgroups varied by age, sex, and racial-ethnic distribution (p<0.001), there was no difference on education or income (p>0.05). After accounting for sex, age, and race-ethnicity, the CoUD subgroup with high PSA had higher odds of antisocial personality disorder (OR=21.96 vs. 6.39, difference-p=8.08×10 -6 ), agoraphobia (OR=4.58 vs. 2.05, difference-p=7.04×10 -4 ), mixed bipolar episode (OR=10.36 vs. 2.61, difference-p=7.04×10 -4 ), posttraumatic stress disorder (OR=11.54 vs. 5.86, difference-p=2.67×10 -4 ), antidepressant medication use (OR=13.49 vs. 8.02, difference-p=1.42×10 -4 ), and sexually transmitted diseases (OR=5.92 vs. 3.38, difference-p=1.81×10 -5 ) than the low-PSA CoUD subgroup.

Conclusions

We found different patterns of PSA in association with psychiatric and somatic comorbidities among CoUD cases within the Yale-Penn cohort. These findings underscore the importance of modeling PSA severity and comorbidities when examining the clinical, molecular, and neuroimaging correlates of CoUD.

Polysubstance Use Patterns among Outpatients Undergoing Substance Use Disorder Treatment: A Latent Class Analysis

Substance Use Disorders (SUDs) pose significant challenges to both individuals and society at large. The primary focus of existing research with clinical SUD populations has been on individual substances, but research is required to better understand the profiles of individuals who use different substances simultaneously. The purpose of the current study was, therefore, to identify patterns of use among subjects (n = 1025) who reported using multiple substances by adopting a Latent Class Analysis (LCA) methodology. The Addiction Severity Index (ASI-lite) was included as a measure of substance misuse, we performed LCA to identify patterns of substance use through the administration of the ASI-Lite. Responses were collected from the following substances: alcohol, cannabis/cannabinoids, opioids and heroin, and cocaine. Results identified two latent classes: (1) alcohol use dominant, and (2) poly-abuser use dominants. Class 1 represented 60.0% of the sample and refers to individuals with the dominant use of alcohol, of those a higher proportion (47%) reported low-frequency use (1 to 7 days per month) and 26% reported a frequency of use of 24 to 30 days per month. Furthermore, 18% used alcohol in combination with cocaine. Class 2 represents 40.0% of the sample. This class is characterized by low-frequency and high-frequency users of several substances. The results obtained highlight the importance of deepening the study of the concomitant use of substances in individuals with SUDs to better understand the health risk of the combined use of two or more substances.

Effect of Combined Methamphetamine and Oxycodone Use on the Synaptic Proteome in an In Vitro Model of Polysubstance Use

Polysubstance use (PSU) generally involves the simultaneous use of an opioid along with a stimulant. In recent years, this problem has escalated into a nationwide epidemic. Understanding the mechanisms and effects underlying the interaction between these drugs is essential for the development of treatments for those suffering from addiction. Currently, the effect of PSU on synapses-critical points of contact between neurons-remains poorly understood. Using an in vitro model of primary neurons, we examined the combined effects of the psychostimulant methamphetamine (METH) and the prescription opioid oxycodone (oxy) on the synaptic proteome using quantitative mass-spectrometry-based proteomics. A further ClueGO analysis and Ingenuity Pathway Analysis (IPA) indicated the dysregulation of several molecular functions, biological processes, and pathways associated with neural plasticity and structural development. We identified one key synaptic protein, Striatin-1, which plays a vital role in many of these processes and functions, to be downregulated following METH+oxy treatment. This downregulation of Striatin-1 was further validated by Western blot. Overall, the present study indicates several damaging effects of the combined use of METH and oxy on neural function and warrants further detailed investigation into mechanisms contributing to synaptic dysfunction.

Social determinants of ethno-racial inequalities in substance use: a decomposition of national survey data

BACKGROUND

Similar to the US, mortality due to suicide and the use of opioids, alcohol, and other substances (so-called "Deaths of Despair"), is rising in Canada and has been disproportionately observed among Whites compared to other racial and ethnic groups. This study aimed to assess the determinants of the ethno-racial differences in the use of substances that underlie these deaths.

METHODS

Using nationally representative data from the Canadian Community Health Survey (2003, 2015-2016, 2018 cycles), a decomposition analysis was performed to estimate the contribution of psychosocial determinants, including age, sex, marital status, immigration, education, income, rurality, and affective health on inequalities between White and non-White populations in illicit substance, opioid, and problematic alcohol use and combined use (≥ 2) of substances.

RESULTS

Overall, White respondents reported higher levels (by 5% to 10%) of substance use than non-White peers. Over 30% of the ethno-racial inequalities in illicit substance, problematic alcohol, and polysubstance use are explained by the protective role of immigration among those who are not White, whose low levels of substance use lower the prevalence in the non-White population overall. Among those born in Canada, no ethno-racial differences in substance use were observed.

CONCLUSION

Social determinants, particularly immigrant status, explain a substantial proportion of ethno-racial inequalities in substance use in Canada. The jump in substance use between racialized populations who immigrated to Canada and those Canadian-born highlights the importance of exploring within-group variability in deaths of despair risk and considering how intersecting forces including systemic racism shape substance use patterns across generations.

Polysubstance use poisoning deaths in Canada: an analysis of trends from 2014 to 2017 using mortality data

Background

Over the past decade, rates of drug poisoning deaths have increased dramatically in Canada. Current evidence suggests that the non-medical use of synthetic opioids, stimulants and patterns of polysubstance use are major factors contributing to this increase.

Methods

Counts of substance poisoning deaths involving alcohol, opioids, other central nervous system (CNS) depressants, cocaine, and CNS stimulants excluding cocaine, were acquired from the Canadian Vital Statistics Death Database (CVSD) for the years 2014 to 2017. We used joinpoint regression analysis and the Cochrane-Armitage trend test for proportions to examine changes over time in crude mortality rates and proportions of poisoning deaths involving more than one substance.

Results

Between 2014 and 2017, the rate of substance poisoning deaths in Canada almost doubled from 6.4 to 11.5 deaths per 100,000 population (Average Annual Percent Change, AAPC: 23%, p < 0.05). Our analysis shows this was due to increased unintentional poisoning deaths (AAPC: 26.6%, p < 0.05) and polysubstance deaths (AAPC: 23.0%, p < 0.05). The proportion of unintentional poisoning deaths involving polysubstance use increased significantly from 38% to 58% among males (p < 0.0001) and 40% to 55% among females (p < 0.0001). Polysubstance use poisonings involving opioids and CNS stimulants (excluding cocaine) increased substantially during the study period (males AAPC: 133.1%, p < 0.01; females AAPC: 118.1%, p < 0.05).

Conclusions

Increases in substance-related poisoning deaths between 2014 and 2017 were associated with polysubstance use. Increased co-use of stimulants with opioids is a key factor contributing to the epidemic of opioid deaths in Canada.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-12678-z.

Towards cross-Canada monitoring of the unregulated street drug supply

Background

The well-being of people who use drugs (PWUD) continues to be threatened by substances of unknown type or quantity in the unregulated street drug supply. Current efforts to monitor the drug supply are limited in population reach and comparability. This restricts capacity to identify and develop measures that safeguard the health of PWUD. This study describes the development of a low-barrier system for monitoring the contents of drugs in the unregulated street supply. Early results for pilot sites are presented and compared across regions.

Methods

The drug content monitoring system integrates a low-barrier survey and broad spectrum urine toxicology screening to compare substances expected to be consumed and those actually in the drug supply. The system prototype was developed by harm reduction pilot projects in British Columbia (BC) and Montreal with participation of PWUD. Data were collected from harm reduction supply distribution site clients in BC, Edmonton and Montreal between May 2018–March 2019. Survey and urine toxicology data were linked via anonymous codes and analyzed descriptively by region for trends in self-reported and detected use.

Results

The sample consisted of 878 participants from 40 sites across 3 regions. Reported use of substances, their detection, and concordance between the two varied across regions. Methamphetamine use was reported and detected most frequently in BC (reported: 62.8%; detected: 72.2%) and Edmonton (58.3%; 68.8%). In Montreal, high concordance was also observed between reported (74.5%) and detected (86.5%) cocaine/crack use. Among those with fentanyl detected, the percentage of participants who used fentanyl unintentionally ranged from 36.1% in BC, 78.6% in Edmonton and 90.9% in Montreal.

Conclusions

This study is the first to describe a feasible, scalable monitoring system for the unregulated drug supply that can contrast expected and actual drug use and compare trends across regions. The system used principles of flexibility, capacity-building and community participation in its design. Results are well-suited to meet the needs of PWUD and inform the local harm reduction services they rely on. Further standardization of the survey tool and knowledge mobilization is needed to expand the system to new jurisdictions.

The uptake of foil from needle and syringe provision services and its role in smoking or snorting heroin among people who inject drugs in Scotland

BACKGROUND

In the UK, legislation was implemented in 2014 allowing needle and syringe provision (NSP) services to offer foil to people who inject drugs (PWID) to encourage smoking rather than injecting. This paper aims to examine the association between foil uptake and smoking or snorting heroin among PWID. This is the first large scale national study to examine foil uptake and smoking or snorting heroin among PWID post legislative change.

METHOD

Data from 1453 PWID interviewed via Scotland's Needle Exchange Surveillance Initiative in 2017-2018 were analysed using multivariate logistic regression.

RESULTS

Overall, 36% of PWID had obtained foil from NSP services in the past six months. The odds of smoking or snorting heroin were higher among those who had obtained foil (Adjusted Odds Ratio (AOR) 3.79 (95% CI 2.98-4.82) p<0.001) compared to those who had not. Smoking or snorting heroin was associated with lower odds of injecting four or more times daily (AOR 0.60 (95% CI 0.40-0.90) p = 0.012) and injecting into the groin or neck (AOR 0.57 (95% CI 0.46-0.71) p<0.001) but increased odds of having had a skin and soft tissue infection (SSTI) (AOR 1.49 (95% CI 1.17-1.89) p = 0.001) and having experienced an overdose (AOR 1.58 (95% CI 1.18-2.10) p = 0.002) both in the past year.

CONCLUSION

The promotion of smoking drugs via foil provision from NSP services may contribute to the package of harm reduction measures for PWID alongside the provision of injecting equipment. We found that those in receipt of foil were more likely to smoke or snort heroin, and that smoking or snorting heroin was associated with a lower likelihood of some risky injecting behaviours, namely frequent injecting and injecting into the groin or neck. But it remains uncertain if the provision of foil can lead to a reduction in health harms, such as SSTI and overdose. Future research is needed to understand PWID motivations for smoking drugs, obtaining foil from NSP services, and its uses particularly among polydrug users.

Understanding opioid overdose risk and response preparedness among people who use cocaine and other drugs: Mixed-methods findings from a large, multi-city study

BACKGROUND

Fatal overdoses involving cocaine (powdered or crack) and fentanyl have increased nationally and in Massachusetts. It is unclear how overdose risk and preparedness to respond to an overdose differs by patterns of cocaine and opioid use. Methods: From 2017 to 2019, we conducted a nine-community mixed-methods study of Massachusetts residents who use drugs. Using survey data from 465 participants with past-month cocaine and/or opioid use, we examined global differences (p < 0.05) in overdose risk and response preparedness by patterns of cocaine and opioid use. Qualitative interviews (n = 172) contextualized survey findings. Results: The majority of the sample (66%) used cocaine and opioids in the past month; 18.9% used opioids alone; 9.2% used cocaine and had no opioid use history; and 6.2% used cocaine and had an opioid use history. Relative to those with a current/past history of opioid use, significantly fewer of those with no opioid use history were aware of fentanyl in the drug supply, carried naloxone, and had received naloxone training. Qualitative interviews documented how people who use cocaine and have no history of opioid use are largely unprepared to recognize and respond to an overdose. Conclusions: Public health efforts are needed to increase fentanyl awareness and overdose prevention preparedness among people primarily using cocaine.

'Resurgent', 'twin' or 'silent' epidemic? A select data overview and observations on increasing psycho-stimulant use and harms in North America

In the early 2000s, increasing prevalence of psycho-stimulant (e.g., crack/cocaine, methamphetamine) use and related harms, including severe adverse health outcomes, was observed among - mostly marginalized - populations of persons using illicit drugs in North America, underscoring an urgent need for interventions options towards improved prevention and treatment. By about 2010, however, the 'opioid crisis', featuring unprecedented use and public health burden, had accelerated into full force in North America, largely muting attention to the psycho-stimulant issue until recently. Recent surveillance data on drug use and related mortality/morbidity from the present decade has documented a marked resurgence of psycho-stimulant use and harms especially in at-risk populations, commonly in direct combination with opioids, across North America, resulting in a 'twin epidemic' comprised of opioids and psycho-stimulants We briefly review select epidemiological data indicators for these developments from the United States and Canada; in the latter jurisdiction, related evidence has been less prevalent and systematic but corroborating the same trends. Evidently, the (widely ongoing) focus on the 'opioid epidemic' as a 'mono-type' drug problem has become an anachronism that requires urgent and appropriate correction. We then briefly consider existing, evidence-based options for - prevention and treatment - interventions targeting psycho-stimulant use and harms, which are substantially more limited and/or less efficacious than those available for problematic opioid use, while presenting major gaps and challenges. The observed resurgence of psycho-stimulants may, indirectly, relate to recent efforts towards curtailing (medical) opioid availability, thereby accelerating demand and supply for both illicit opioids and psycho-stimulants. The presently unfolding 'twin epidemic' of opioids and psycho-stimulants, combined with limited intervention resources, presents an acute challenge for public health and may crucially undermine actively extensive efforts to reduce opioid-related health harms in North America.

One Is Not Enough: Understanding and Modeling Polysubstance Use

Substance use disorder (SUD) is a chronic, relapsing disease with a highly multifaceted pathology that includes (but is not limited to) sensitivity to drug-associated cues, negative affect, and motivation to maintain drug consumption. SUDs are highly prevalent, with 35 million people meeting criteria for SUD. While drug use and addiction are highly studied, most investigations of SUDs examine drug use in isolation, rather than in the more prevalent context of comorbid substance histories. Indeed, 11.3% of individuals diagnosed with a SUD have concurrent alcohol and illicit drug use disorders. Furthermore, having a SUD with one substance increases susceptibility to developing dependence on additional substances. For example, the increased risk of developing heroin dependence is twofold for alcohol misusers, threefold for cannabis users, 15-fold for cocaine users, and 40-fold for prescription misusers. Given the prevalence and risk associated with polysubstance use and current public health crises, examining these disorders through the lens of co-use is essential for translatability and improved treatment efficacy. The escalating economic and social costs and continued rise in drug use has spurred interest in developing preclinical models that effectively model this phenomenon. Here, we review the current state of the field in understanding the behavioral and neural circuitry in the context of co-use with common pairings of alcohol, nicotine, cannabis, and other addictive substances. Moreover, we outline key considerations when developing polysubstance models, including challenges to developing preclinical models to provide insights and improve treatment outcomes.

Conditioned taste avoidance induced by the combination of heroin and cocaine: Implications for the use of speedball

Speedball (heroin + cocaine) is a prevalent drug combination among intravenous drug users. Although its use is generally discussed to be a function of changes in the rewarding effects of either or both drugs, changes in the aversive effects of either drug may also be impacted (weakened) by the combination. To address this latter possibility and its potential role in the use of speedball, the present studies examined the interaction of cocaine and heroin in taste avoidance conditioning. In Experiment 1, male Sprague-Dawley rats were given access to a novel saccharin solution and then injected with either vehicle or heroin (3.2 mg/kg, IP) followed immediately by various doses of cocaine (10, 18 or 32 mg/kg, SC). At the two lowest doses of cocaine, only animals injected with the drug combination (H + C) displayed a taste avoidance relative to control subjects (taste avoidance was induced with both the combination and the high dose of cocaine). At no dose did animals injected with the combination of heroin and cocaine drink more than animals injected with cocaine alone. In Experiment 2, male Sprague-Dawley rats were similarly treated but injected with vehicle or cocaine (10 mg/kg) followed by injections of various doses of heroin (1.8, 3.2, 5.6 or 10 mg/kg). At the three highest doses of heroin, only animals injected with the drug combination (C + H) displayed significant avoidance relative to control subjects (no avoidance was evident with the combination of cocaine and the low dose of heroin). At no dose did animals injected with the combination of cocaine and heroin drink more than animals injected with heroin alone. Together, these results suggest that the aversive effects of heroin and cocaine are not attenuated by co-administration by cocaine and heroin, respectively. The importance of this for the use of speedball was discussed.

Chronic pain management among people who use drugs: A health policy challenge in the context of the opioid crisis

BACKGROUND

In Canada, the rise in prescription opioid (PO) overdoses and addiction is a major public health concern. Various health authorities have recently recommended that physicians use caution when prescribing opioids, especially to people with histories of substance use. As a result, fewer therapeutic options are available for people who use drugs (PWUD) and suffer from chronic non-cancer pain (CNCP). This paper examines how PWUD describe their experiences with CNCP management in the context of the opioid crisis.

METHODS

This qualitative study is based on in-depth interviews with Montreal (Canada) PWUD experiencing CNCP for 3 months or more.

RESULTS

Most of the 25 participants (27-61 years; 10 women, 15 men) were polysubstance users (cocaine, opioids, amphetamine, etc.) suffering from CNCP for several years, with multiple additional health and social problems. The majority were unsatisfied with their CNCP management. They felt labelled as "addicts" and stigmatized within the healthcare system. Many participants had been denied PO, even those with severe CNCP and those who were not opioid-dependent. Participants expressed a desire to access non-pharmacological CNCP therapies, but these were often too expensive. Some PWUD were offered methadone to relieve CNCP and found this inappropriate. As a last resort several participants reported self-medicating CNCP with street drugs, increasingly known to be laced with fentanyl.

CONCLUSION

PWUD with CNCP are affected by two opioid crises: the PO crisis and the street-opioid crisis. The lack of a coherent policy that addresses their pain management produces reoccurring problems when seeking CNCP relief. Restrictive prescription measures implemented in response to the PO crisis may have consequences similar to prohibitionist policies: they heighten overdose risks for PWUD by increasing exposure to street drugs laced with fentanyl. Improving access to diverse CNCP management options for PWUD can help reduce harms related to street-opioid use.

Latent Risk Subtypes Based on Injection and Sexual Behavior Among People Who Inject Drugs in Rural Puerto Rico

BACKGROUND

People who inject drugs (PWID) in Puerto Rico engage in high levels of injection and sexual risk behavior, and they are at high risk for HIV and hepatitis C (HCV) infection, relative to their US counterparts. Less is known, however, about the clustering of risk behavior conducive to HIV and HCV infection among rural Puerto Rican communities.

OBJECTIVES

The purpose of this study was to examine concurrent injection and sexual risk subtypes among a rural sample of PWID in Puerto Rico.

METHODS

Data were drawn from a respondent-driven sample collected in 2015 of 315 PWID in 4 rural communities approximately 30-40 miles from San Juan. Latent class analysis (LCA) was used to examine risk subtypes using 3 injection and 3 sexual risk indicators. In addition, demographic and other PWID characteristics were examined as possible predictors of latent class membership.

RESULTS

Four LCA subtypes were identified: low risk (36%), high injection/low sexual risk (22%), low injection/high sexual risk (20%), and high risk (22%). Younger age and past year homelessness predicted high risk latent class membership, relative to the other classes. In addition, daily speedball use predicted membership in the high injection/low sexual risk class, relative to the low risk and low injection/high sexual risk classes.

CONCLUSION/IMPORTANCE

The findings suggest ways in which PWID risk clusters can be identified for targeted interventions.

Patterns of substance use and mortality risk in a cohort of 'hard-to-reach' polysubstance users

AIMS

To examine the mortality risk in a cohort of 'hard-to-reach' polysubstance users and its putative associations with substance use. Specifically, we estimated all-cause mortality risk as a function of individual substance use indicators, and then as a function of their complex, 'real-life' patterns as identified through latent class analysis (LCA).

DESIGN

Prospective cohort study among street- and low-threshold service-recruited polysubstance users included between September and November 2013 and followed through the National Cause of Death Registry until 31 October 2015.

SETTING

Seven Norwegian cities.

PARTICIPANTS

A total of 884 users of illegal opioids and/or stimulants. Of these, 357 were in opioid substitution treatment (OST) at the time of inclusion. Forty-four participants died during follow-up.

MEASUREMENTS

Primary outcome: all-cause mortality risk. Unadjusted and adjusted Cox proportional hazard (PH) regression models (covariates: male, age, homelessness/shelter use, overdose experience, OST status, years of injecting, individual substance use indicators, city, use patterns). LCA models estimated separately for those in and those not in OST due to measurement invariance.

FINDINGS

The crude mortality rate was 2.52 per 100 person-years. Standardized mortality ratio was 26.11 [95% confidence interval (CI) = 10.06-54.87] for women and 10.71 (95% CI = 6.39-16.81) for men. No single drug use indicator, such as 'heroin injection' or 'number of drugs used', was associated with the mortality risk. However, meaningful use patterns were identified; three OST and non-OST patterns each. The non-OST patterns 'polysubstance injectors' [hazard ratio (HR) = 3.45, 95% CI = 0.98-12.14] and 'low frequent injectors' (HR = 3.17, CI = 1.05-9.56) were associated significantly with the mortality risk even when adjusted for other known risk factors.

CONCLUSIONS

In a Norwegian prospective cohort study, 'hard-to-reach' polysubstance users had a more than 10 times higher mortality risk than the general population. Mortality risk was not a function of any single drug use indicator, but two distinct combinations of substances, frequencies and routes of administration were associated with the mortality risk.

Polydrug Use and Heterogeneity in HIV Risk Among People Who Inject Drugs in Estonia and Russia: A Latent Class Analysis

Non-medical drug injection is a major risk factor for HIV infection in Russia and Estonia. Multiple drug use (polydrug) has further been associated with increased harms. We compared HIV, injecting and sexual risk associated with polydrug use among people who injected drugs (PWID) in 2012–2013 in Kohtla-Järve (Estonia, n = 591) and St Petersburg (Russia, n = 811). Using latent class analysis, we identified five (poly)drug classes, the largest consisting of single-drug injectors among whom an opioid was the sole drug injected (56% of PWID). The four remaining polydrug classes included polydrug-polyroute injectors who injected and used opiates and stimulants (9%), opiate-stimulant poly-injectors who injected amphetamine-type-stimulants with a primary opiate (7%) and opiate-opioid poly-injectors who injected opioids and opiates (16%). Non-injection stimulant co-users were injectors who also used non-injection stimulants (12%). In multivariable multinomial regressions, all four polydrug classes were associated with greater injection risks than single-drug injection, while opiate-stimulant and opiate-opioid poly-injection were also associated with having multiple sex partners. Riskier behaviours among polydrug-injectors suggest increased potential for transmission of blood-borne and sexually-transmitted infections. In addition to needles/syringes provision, services tailored to PWID drug and risk profiles, could consider drug-appropriate treatment and sexual risk reduction strategies to curb HIV transmission.

Drug use and phylogenetic clustering of hepatitis C virus infection among people who use drugs in Vancouver, Canada: A latent class analysis approach

This study estimated latent classes (ie, unobserved subgroups in a population) of people who use drugs in Vancouver, Canada, and examined how these classes relate to phylogenetic clustering of hepatitis C virus (HCV) infection. HCV antibody-positive people who use drugs from two cohorts in Vancouver, Canada (1996-2012), with a Core-E2 sequence were included. Time-stamped phylogenetic trees were inferred, and phylogenetic clustering was determined by time to most common recent ancestor. Latent classes were estimated, and the association with the phylogenetic clustering outcome was assessed using an inclusive classify/analyse approach. Among 699 HCV RNA-positive participants (26% female, 24% HIV+), recent drug use included injecting cocaine (80%), injecting heroin (70%), injecting cocaine/heroin (ie, speedball, 38%) and crack cocaine smoking (28%). Latent class analysis identified four distinct subgroups of drug use typologies: (i) cocaine injecting, (ii) opioid and cocaine injecting, (iii) crack cocaine smoking and (iv) heroin injecting and currently receiving opioid substitution therapy. After adjusting for age and HIV infection, compared to the group defined by heroin injecting and currently receiving opioid substitution therapy, the odds of phylogenetic cluster membership was greater in the cocaine injecting group (adjusted OR [aOR]: 3.06; 95% CI: 1.73, 5.42) and lower in the crack cocaine smoking group (aOR: 0.06; 95% CI: 0.01, 0.48). Combining latent class and phylogenetic clustering analyses provides novel insights into the complex dynamics of HCV transmission. Incorporating differing risk profiles associated with drug use may provide opportunities to further optimize and target HCV treatment and prevention strategies.

Rural and urban comparisons of polysubstance use profiles and associated injection behaviors among people who inject drugs in Puerto Rico

INTRODUCTION

In contrast to urban populations, little is known about polysubstance use among rural people who inject drugs (PWID), particularly in Puerto Rico where injection drug use and related health consequences are prevalent. The aim of the study is to compare injection and non-injection substance use profiles among separate urban and rural samples of Puerto Rican PWID.

MATERIAL AND METHODS

Data for the urban sample come from 455 PWID who participated in the CDC's National HIV Behavioral Surveillance survey of injection drug use in San Juan. The data for the rural sample come from 315 PWID residing in four rural cities approximately 40-miles from San Juan. Latent class analysis was used to derive separate urban and rural profiles of weekly injection and non-injection substance use. Injection behaviors were examined as possible correlates of latent class membership.

RESULTS

Five latent classes were identified in the urban sample, and three latent classes were identified in the rural sample. Classes were similar across samples; however, key differences emerged. Both samples had classes of primary heroin injectors, primary speedball injectors, and cocaine-heroin injectors. The urban sample had one high polysubstance class. Polysubstance use profiles that shared similar characteristics between samples also shared similar injection patterns, with some variation.

DISCUSSION

Variations in substance use patterns and associated health risks are likely shaped by social and geographic boundaries.

CONCLUSIONS

Understanding variations in substance use patterns across rural and urban locales may improve surveillance efforts and tailor desistance and harm reduction efforts at the state and local levels.

Polydrug use and its association with drug treatment outcomes among primary heroin, methamphetamine, and cocaine users

BACKGROUND

Polydrug use may challenge effective treatment for substance use disorders. We evaluate whether secondary substance use modifies the association between treatment and primary drug use among primary heroin, cocaine and methamphetamine (MA) users.

METHODS

Data were obtained from prospective cohort studies on people who use illicit drugs (PWUD) in California, USA. Using repeated monthly data on self-reported secondary substance use (heroin, cocaine, MA, alcohol or marijuana; ≥1day in a month), primary drug use (≥1day in a month), and treatment participation, collected via timeline follow-back, we fitted generalized linear mixed multiple regression models controlling for potential confounders to examine the interactions between treatment and secondary substance use on the odds of primary heroin, cocaine and MA use, respectively.

RESULTS

Included in our study were 587 primary heroin, 444 primary MA, and 501 primary cocaine users, with a median of 32.4, 13.3 and 18.9 years of follow-up, respectively. In the absence of secondary substance use, treatment was strongly associated with decreased odds of primary drug use (adjusted odds ratios (aORs): 0.25, 95% CI: 0.24, 0.27, 0.07 (0.06, 0.08), and 0.07 (0.07, 0.09)) for primary heroin, MA, and cocaine users, respectively. Secondary substance use of any kind moderated these associations (0.82 (0.78, 0.87), 0.25 (0.21, 0.30) and 0.53 (0.45, 0.61), respectively), and these findings were consistent for each type of secondary substance considered. Moreover, we observed different associations in terms of direction and magnitude between secondary substance use and primary drug use during off-treatment periods across substance types.

CONCLUSION

This study demonstrates secondary substance use moderates the temporal associations between treatment and primary drug use among primary heroin, MA and cocaine users. Disparate patterns of polydrug use require careful measurement and analysis to inform targeted treatment for polydrug users.

"I love having benzos after my coke shot": The use of psychotropic medication among cocaine users in downtown Montreal

BACKGROUND

Cocaine abuse is a major public health issue due to its role in the HIV and hepatitis C virus (HCV) epidemics in North America. A significant area of concern among people who use cocaine (PWUC), injected or smoked, is their frequent misuse of prescription drugs, particularly psychotropic medication (PM), such as tranquilizers, sedatives, stimulants, and antipsychotics. This paper aims to describe and understand practices of PM use among PWUC in downtown Montreal.

METHOD

Ethnographic methods including participant observation and semi-structured interviews were used in an iterative manner.

RESULTS

Two thirds of the 50 participants were male. They ranged in age from 20 to 60 and most were homeless. A significant proportion of them reported polydrug use patterns that included frequent concomitant opioid use (heroin and/or prescription opioids (PO)). Benzodiazepine-based tranquilizers and the atypical antipsychotic quetiapine were the most frequently used PM. Routes of PM administration were oral, nasal and, to a lesser degree, intravenous. Five main PM use practices were identified: 1) "downers" from cocaine high (benzodiazepines and quetiapine); 2) enhancers of heroin/PO effects (benzodiazepines); 3) reducers or suppressors of heroin/PO withdrawal symptoms (benzodiazepines); 4) enablers of a different type of "trip" (benzodiazepines); and 5) treatment for mental and physical problems (benzodiazepines and quetiapine).

CONCLUSION

PM use practices showed several complementary functions that PM fulfill in a context of polydrug use. The soothing and stimulating effects of PM reinforce the patterns of drug use among participants, posing various risks including overdose, HIV/HCV transmission, PM dependence and accidents. The results highlight the need for clinicians to assess clients' substance use patterns when prescribing PM and to question PWUC about PM use. The findings also underline certain unmet service needs in relation to overdose, HIV/HCV and mental health prevention/treatment among cocaine users.

Latent classes of polydrug and polyroute use and associations with human immunodeficiency virus risk behaviours and overdose among people who inject drugs in Tijuana, Baja California, Mexico

INTRODUCTION AND AIMS

Patterns of polydrug use among people who inject drugs (PWID) may be differentially associated with overdose and unique human immunodeficiency virus (HIV) risk factors. Subgroups of PWID in Tijuana, Mexico, were identified based on substances used, route of administration, frequency of use and co-injection indicators.

DESIGN AND METHODS

Participants were PWID residing in Tijuana age ≥18 years sampled from 2011 to 2012 who reported injecting an illicit substance in the past month (n = 735). Latent class analysis identified discrete classes of polydrug use characterised by 11 indicators of past 6 months substance use. Multinomial logistic regression examined class membership association with HIV risk behaviours, overdose and other covariates using an automated three-step procedure in mplus to account for classification error.

RESULTS

Participants were classified into five subgroups. Two polydrug and polyroute classes were defined by use of multiple substances through several routes of administration and were primarily distinguished from each other by cocaine use (class 1: 5%) or no cocaine use (class 2: 29%). The other classes consisted primarily of injectors: cocaine, methamphetamine and heroin injection (class 3: 4%); methamphetamine and heroin injection (class 4: 10%); and heroin injection (class 5: 52%). Compared with the heroin-only injection class, memberships in the two polydrug and polyroute use classes were independently associated with both HIV injection and sexual risk behaviours.

DISCUSSION AND CONCLUSIONS

Substance use patterns among PWID in Tijuana are highly heterogeneous, and polydrug and polyroute users are a high-risk subgroup who may require more tailored prevention and treatment interventions. [Meacham MC, Roesch SC, Strathdee SA, Lindsay S, Gonzalez-Zuniga P, Gaines TL. Latent classes of polydrug and polyroute use and associations with human immunodeficiency virus risk behaviours and overdose among people who inject drugs in Tijuana, Baja California, Mexico. Drug Alcohol Rev 2018;37:128-136].

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.

Epidemiology of Injection Drug Use: New Trends and Prominent Issues

After more than 30 years of research, numerous studies have shown that injection drug use is associated with a wide range of adverse health outcomes such as drug overdoses, drug-related suicidal behaviours, comorbid psychiatric disorders, bloodborne pathogens and other infectious diseases, and traumas. This review explores new trends and prominent issues associated with injection drug use. The dynamic nature of injection drug use is underlined by examining its recent trends and changing patterns in Canada and other "high-income countries." Three research topics that could further contribute to the development of comprehensive prevention and intervention strategies aimed at people who inject drugs are also discussed: risk behaviours associated with the injection of prescription opioids, binge injection drug use, and mental health problems as determinants of injection risk behaviours.

Risk Factors Associated with Unsafe Injection Practices at the First Injection Episode among Intravenous Drug Users in France: Results from PrimInject, an Internet Survey

Background. New drug use patterns may increase the risk of human immunodeficiency virus and hepatitis infections. In France, new injection patterns among youths with diverse social backgrounds have emerged, which may explain the persistently high rates of hepatitis C virus infection. This study explores factors associated with injection risk behaviours at first injection among users who began injecting in the post-2000 era. Methods. A cross-sectional study was conducted on the Internet from October 2010 to March 2011, through an online questionnaire. Multivariate logistic regression identified the independent correlates of needle sharing and equipment (cooker/cotton filter) sharing. Results. Among the 262 respondents (mean age 25 years), 65% were male. Both risk behaviours were positively associated with initiation before 18 years of age (aOR 3.7 CI 95% 1.3–10.6 and aOR 3.0 CI 95% 1.3–7.0) and being injected by another person (aOR 3.1 CI 95% 1.0–9.9 and aOR 3.0 CI 95% 1.3–7.1). Initiation at a party was an independent correlate of equipment sharing (aOR 2.6 95% CI 1.0–6.8). Conclusions. Results suggest a need for innovative harm reduction programmes targeting a variety of settings and populations, including youths and diverse party scenes. Education of current injectors to protect both themselves and those they might initiate into injection is critically important.

Licit and illicit substance use among people who inject drugs and the association with subsequent suicidal attempt

AIM

To estimate associations between recent licit and illicit substance use and subsequent suicide attempt among people who inject drugs (PWID).

DESIGN

Secondary analysis of longitudinal data from a prospective cohort study of PWID followed bi-annually between 2004 and 2011.

SETTING

Montréal, Canada.

PARTICIPANTS

Seven hundred and ninety-seven PWID who reported injection drug use in the previous 6 months, contributing to a total of 4460 study visits. The median number of visits per participant was five (interquartile range: 3-8).

MEASUREMENTS

An interviewer-administered questionnaire eliciting information on socio-demographic factors, detailed information on substance use patterns and related behaviours, mental health markers and suicide attempt. The primary exposure variables examined were past-month use of alcohol [heavy (≥ 60 drinks); moderate (one to 59 drinks); none], sedative-hypnotics, cannabis, cocaine, amphetamine and opioids [regular (≥ 4 days); occasional (1-3 days); none]. The outcome was a binary measure of suicide attempt assessed in reference to the previous 6 months.

FINDINGS

In multivariate analyses, a positive association was found among licit substances between heavy alcohol consumption [adjusted odds ratio (AOR) = 2.05; 95% confidence interval (CI) = 1.12-3.75], regular use of sedative-hypnotics (AOR = 1.89; 95% CI = 1.21-2.95) and subsequent attempted suicide. Among illicit substances, occasional use of cannabis (AOR = 1.84; 95% CI = 1.09-3.13) had a positive association with subsequent suicide attempt. No statistically significant association was found for the remaining substances.

CONCLUSION

Among people who inject drugs, use of alcohol, sedative-hypnotics and cannabis, but not cocaine, amphetamine or opioids, appears to be associated with an increased likelihood of later attempted suicide.

White matter deficits assessed by diffusion tensor imaging and cognitive dysfunction in psychostimulant users with comorbid human immunodeficiency virus infection

BACKGROUND

Psychostimulant drug use is commonly associated with drug-related infection, including the human immunodeficiency virus (HIV). Both psychostimulant use and HIV infection are known to damage brain white matter and impair cognition. To date, no study has examined white matter integrity using magnetic resonance imaging (MRI) diffusion tensor imaging (DTI) in chronic psychostimulant users with comorbid HIV infection, and determined the relationship of white matter integrity to cognitive function.

METHODS

Twenty-one subjects (mean age 37.5 ± 9.0 years) with a history of heavy psychostimulant use and HIV infection (8.7 ± 4.3 years) and 22 matched controls were scanned on a 3T MRI. Fractional anisotropy (FA) values were calculated with DTI software. Four regions of interest were manually segmented, including the genu of the corpus callosum, left and right anterior limbs of the internal capsule, and the anterior commissure. Subjects also completed a neurocognitive battery and questionnaires about physical and mental health.

RESULTS

The psychostimulant using, HIV positive group displayed decreased white matter integrity, with significantly lower FA values for all white matter tracts (p < 0.05). This group also exhibited decreased cognitive performance on tasks that assessed cognitive set-shifting, fine motor speed and verbal memory. FA values for the white matter tracts correlated with cognitive performance on many of the neurocognitive tests.

CONCLUSIONS

White matter integrity was thus impaired in subjects with psychostimulant use and comorbid HIV infection, which predicted worsened cognitive performance on a range of tests. Further study on this medical comorbidity is required.

Anxiety, mood disorders and injection risk behaviors among cocaine users: Results from the COSMO study

BACKGROUND AND OBJECTIVES

Despite being common among cocaine users, mental health problems and their relationship with HIV and hepatitis C high risk injection behaviors are poorly documented. This study was undertaken to examine the relationships between mood and anxiety disorders and the sharing of drug injection equipment among cocaine users who inject drugs.

METHODS

The sample was drawn from a prospective cohort study and comprised of 387 participants. The outcome of interest was "sharing injection material" in the past 3 months. The presence of mood and anxiety disorders during the past year was assessed using the CIDI questionnaire. Statistical analyses were conducted on baseline data using logistic regression.

RESULTS

Most participants were male (84.5%) and were aged 25 or over (92.2%); 43.0% qualified for an anxiety disorder diagnosis and 29.3% for a mood disorder diagnosis. Participants with anxiety disorders were more likely to share needles (Adjusted Odds Ratio [AOR]: 2.13, 95%CI: 1.15-3.96) and other injection material (AOR: 1.81, 95%CI: 1.12-2.92). No significant association was found between mood disorders and sharing behaviors.

DISCUSSION AND CONCLUSIONS

Primary anxiety disorders but not mood disorders increases injection risk behaviors among cocaine users. These results bring to light another negative outcome of mental health comorbidity in this vulnerable population.

SCIENTIFIC SIGNIFICANCE

This study underlines the need to fine-tune therapeutic approaches targeting specific mental health problems in individuals with cocaine use disorders. Longitudinal studies that assess impulsivity and other correlates of psychiatric disorders are needed to examine underlying mechanisms of high risk injection behaviors in comorbid populations.

Independent effects of HIV infection and cocaine dependence on neurocognitive impairment in a community sample living in the southern United States

BACKGROUND

Prior studies have established that methamphetamine and HIV can have additive deleterious effects on neurocognitive functioning, but there has been relatively little research on other stimulants like cocaine. This study investigated the effects of cocaine and HIV on neurocognitive impairment in a large, well-characterized sample.

METHODS

The sample included 193 adults across four groups: HIV-positive cocaine users (n = 48), HIV-negative cocaine users (n = 53), HIV-positive non-drug users (n = 60), and HIV-negative non-drug users (n = 32). Cocaine users met criteria for lifetime dependence and had past-month cocaine use. A comprehensive battery assessed substance abuse and neurocognitive functioning.

RESULTS

Participants were mostly male (66%) and African-American (85%), with a mean age of 46.09 years. The rate of global impairment was 33%, with no significant main effects across groups on likelihood of impairment. There were main effects for cocaine on processing speed and executive functioning, with cocaine users having greater impairment (F = 9.33 and F = 4.22, respectively), and for HIV on attention, with HIV-infected persons having greater impairment (F = 5.55). There was an interaction effect for executive functioning, with the three patient groups having greater impairment than controls (F = 5.05). Nonparametric analyses revealed significant additive impairment in the presence of both HIV and cocaine for processing speed.

CONCLUSIONS

While cocaine does not appear to increase vulnerability to global HIV-associated neurocognitive impairment, it does have independent adverse effects on executive functioning and processing speed. Given prior evidence that domain-specific deficits predict real-world impairments, our results may help explain the poorer behavioral and functional outcomes observed in HIV-infected cocaine users.

Exploration of a crack use setting and its impact on drug users' risky drug use and sexual behaviors: the case of piaules in a Montréal neighborhood

From July 2011, a one-year study based on ethnographic methodology was carried out in "crack houses" in the neighborhood of Hochelaga-Maisonneuve in Montréal, Canada. The study aimed to explore the operational style of a specific indoor drug use setting and its impact on users' risky sexual and drug use behaviors in a context of drug market change. A thematic analysis of observational and interview notes was conducted. This study stresses the importance to examine the role of environmental factors in relation to crack smoking's health-related risks and to complement individual-based interventions with structural strategies. The study's limitations are noted.

Polydrug Use and HIV Risk Among People Who Inject Heroin in Tijuana, Mexico: A Latent Class Analysis

BACKGROUND

Although most people who inject drugs (PWID) in Tijuana, Mexico, primarily inject heroin, injection and non-injection use of methamphetamine and cocaine is common. We examined patterns of polydrug use among heroin injectors to inform prevention and treatment of drug use and its health and social consequences.

METHODS

Participants were PWID residing in Tijuana, aged ≥18 years who reported heroin injection in the past six months and were recruited through respondent-driven sampling (n = 1,025). Latent class analysis was conducted to assign individuals to classes on a probabilistic basis, using four indicators of past six-month polydrug and polyroute use: cocaine injecting, cocaine smoking or snorting, methamphetamine injecting, and methamphetamine smoking or snorting. Latent class membership was regressed onto covariates in a multinomial logistic regression.

RESULTS

Latent class analyses testing 1, 2, 3, and 4 classes were fit, with the 3-class solution fitting best. Class 1 was defined by predominantly heroin use (50.2%, n = 515); class 2 by methamphetamine and heroin use (43.7%, n = 448), and class 3 by methamphetamine, cocaine, and heroin use (6.0%, n = 62). Bivariate and multivariate analyses indicated a group of methamphetamine and cocaine users that exhibited higher-risk sexual practices and lower heroin injecting frequency, and a group of methamphetamine users who were younger and more likely to be female.

CONCLUSIONS

Discrete subtypes of heroin PWID were identified based on methamphetamine and cocaine use patterns. These findings have identified subtypes of heroin injectors who require more tailored interventions to reduce the health and social harms of injecting drug use.

Estimating the size of the population of persons who inject drugs in the island of Montréal, Canada, using a six-source capture-recapture model

BACKGROUND

To plan and implement services to persons who inject drugs (PWID), knowing their number is essential. For the island of Montréal, Canada, the only estimate, of 11,700 PWID, was obtained in 1996 through a capture-recapture method. Thirteen years later, this study was undertaken to produce a new estimate.

METHODS

PWID were defined as individuals aged 14-65 years, having injected recently and living on the island of Montréal. The study period was 07/01/2009 to 06/30/2010. An estimate was produced using a six-source capture-recapture log-linear regression method. The data sources were two epidemiological studies and four drug dependence treatment centres. Model selection was conducted in two steps, the first focusing on interactions between sources and the second, on age group and gender as covariates and as modulators of interactions.

RESULTS

A total of 1480 PWID were identified in the six capture sources. They corresponded to 1132 different individuals. Based on the best-fitting model, which included age group and sex as covariates and six two-source interactions (some modulated by age), the estimated population was 3910 PWID (95% confidence intervals (CI): 3180-4900) which represents a prevalence of 2.8 (95% CI: 2.3-3.5) PWID per 1000 persons aged 14-65 years.

CONCLUSIONS

The 2009-2010 estimate represents a two-third reduction compared to the one for 1996. The multisource capture-recapture method is useful to produce estimates of the size of the PWID population. It is of particular interest when conducted at regular intervals thus allowing for close monitoring of the injection phenomenon.

A social network-informed latent class analysis of patterns of substance use, sexual behavior, and mental health: Social Network Study III, Winnipeg, Manitoba, Canada

OBJECTIVES

We assessed whether a meaningful set of latent risk profiles could be identified in an inner-city population through individual and network characteristics of substance use, sexual behaviors, and mental health status.

METHODS

Data came from 600 participants in Social Network Study III, conducted in 2009 in Winnipeg, Manitoba, Canada. We used latent class analysis (LCA) to identify risk profiles and, with covariates, to identify predictors of class.

RESULTS

A 4-class model of risk profiles fit the data best: (1) solitary users reported polydrug use at the individual level, but low probabilities of substance use or concurrent sexual partners with network members; (2) social-all-substance users reported polydrug use at the individual and network levels; (3) social-noninjection drug users reported less likelihood of injection drug and solvent use; (4) low-risk users reported low probabilities across substances. Unstable housing, preadolescent substance use, age, and hepatitis C status predicted risk profiles.

CONCLUSIONS

Incorporation of social network variables into LCA can distinguish important subgroups with varying patterns of risk behaviors that can lead to sexually transmitted and bloodborne infections.

Changing patterns of first injection across key periods of the French Harm Reduction Policy: PrimInject, a cross sectional analysis

BACKGROUND

Monitoring of emerging modes of drug consumption in France has identified new patterns of injection among youths with diverse social backgrounds, which may explain the persistence of high rates of hepatitis C virus infection. The circumstances surrounding the first injection have been poorly documented in the group of heavy drug users and in the context of the French opioid substitution treatment (OST) policy that provides expanded access to high-dosage buprenorphine (BHD) METHODS: An Internet survey (Priminject) was conducted from October 2010 to March 2011 with French drug users. Four time periods were compared based on critical dates throughout the implementation of the Harm Reduction Policy in France.

RESULTS

Compared with drug users who injected for the first time prior to 1995, the aspects of drug use for users who recently injected for the first time were as follows: (1) experimentation with miscellaneous drugs before the first injection; (2) an older age at the time of first injection; (3) heroin as the drug of choice for an individual's first injection, notwithstanding the increased usage of stimulant drugs; (4) BHD did not appear to be a pathway to injection; and (5) an increased number of users who injected their first time alone, without the help or presence of another individual.

CONCLUSION

The PrimInject study showed that there is a group of injection drug users that is larger than the group of injection drug users observed in previous studies; therefore, it is necessary to diversify programs to reach the entire spectrum of high-risk users.