Patterns of heroin and cocaine injection and plasma HIV-1 RNA suppression among a long-term cohort of injection drug users

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Abstract

Background

Previous studies suggest that active drug use may compromise HIV treatment among HIV-positive injection drug users (IDU). However, little is known about the differential impacts of cocaine injection, heroin injection, and combined cocaine and heroin injection on plasma HIV-1 RNA suppression.

Methods

Data were derived from a longstanding open prospective cohort of HIV-positive IDU in Vancouver, Canada. Kaplan–Meier methods and Cox proportional hazards regression were used to examine the impacts of different drug use patterns on rates of plasma HIV-1 RNA suppression.

Results

Between May 1996 and April 2008, 267 antiretroviral (ART) naïve participants were seen for a median follow-up duration of 50.6 months after initiating ART. The incidence density of HIV-1 RNA suppression was 65.2 (95%CI: 57.0–74.2) per 100 person-years. In Kaplan–Meier analyses, compared to those who abstained from injecting, individuals injecting heroin, cocaine, or combined heroin/cocaine at baseline were significantly less likely to achieve viral suppression (all p < 0.01). However, none of the drug use categories remained associated with a reduced rate of viral suppression when considered as time-updated variables (all p > 0.05).

Conclusions

Active injecting at the time of ART initiation was associated with lower plasma HIV-1 RNA suppression rates; however, there was no difference in suppression rates when drug use patterns were examined over time. These findings imply that adherence interventions for active injectors should optimally be applied at the time of ART initiation.

Introduction

Injection drug users (IDU) continue to account for a substantial proportion of new HIV infections globally, and in some areas with rapidly growing epidemics of HIV infection, IDU account for the majority of new infections (UNAIDS, 2008). While recent medical advances in the treatment of HIV disease have resulted in substantial reductions in AIDS-related morbidity and mortality (Egger et al., 2002, Hammer et al., 1997, Wood et al., 2003a, Wood et al., 2003b), a growing body of evidence indicates that not all populations affected by HIV disease have benefited equally from available treatments (Aceijas et al., 2006, Chander et al., 2006, Poundstone et al., 2001). For example, IDU experience many barriers to accessing highly active antiretroviral therapy (ART) and suffer from low rates of adherence once initiated (Aceijas et al., 2006, Mocroft et al., 1999, Wood et al., 2003b); as a consequence, this population often has poorer AIDS-related outcomes (Egger et al., 2002, Lucas et al., 2001, Palepu et al., 2003).

Ongoing illicit drug use among HIV-positive IDU remains a common clinical presentation that raises significant concerns for healthcare providers considering when to initiate ART (Ding et al., 2005, Loughlin et al., 2004, Maisels et al., 2001). This is due in part to a body of evidence indicating that active drug use is associated with lower rates of adherence to ART and suppression of HIV RNA (Arnsten et al., 2002, Egger et al., 2002, Lucas et al., 1999, Lucas et al., 2001, Palepu et al., 2003, Weber et al., 2009). However, while negative impacts of active drug use on HIV-related clinical outcomes have been shown in several studies, little is known about the relationship between specific drugs and patterns of use on outcomes associated with HIV disease (Krüsi et al., 2010). A small number of studies have revealed adverse effects of crack cocaine use (Moss et al., 2004, Sullivan et al., 2007, Baum et al., 2009) and stimulant use more generally (Hinkin et al., 2007, Kapadia et al., 2005) on adherence and progression to AIDS. However, we know of no longitudinal studies that have sought to compare the distinct effects of different drugs on outcomes associated with the treatment of HIV disease, despite recent calls for this type of research (Krüsi et al., 2010). In addition, questions remain concerning the relative contributions of other behavioral factors to poor clinical outcomes among IDU (Krüsi et al., 2010, Wood et al., 2008).

Vancouver, Canada, is home to a large injection-drug-related HIV epidemic that is unique because of the widespread availability of several different types of illegal drugs, including injection cocaine and heroin (Wood and Kerr, 2006). This unique context and the presence of a large, longstanding prospective cohort study of HIV-positive IDU conducted within a context of universal access to free healthcare afforded the opportunity to examine the impact of different types of illicit drug use on suppression of HIV-1 RNA.

Section snippets

Methods

The AIDS Care Cohort to Evaluate Exposure to Survival Services (ACCESS) is a prospective observational cohort of HIV-seropositive injection drug users in Vancouver, Canada. The cohort has been described in detail previously (Wood et al., 2008) and was populated through snowball sampling and extensive street outreach methods in the city's Downtown Eastside. Individuals were eligible for ACCESS if they were aged 18 years or older, HIV-seropositive, had used injection drugs at least once in the

Results

Among these 267 participants, 124 (46.4%) were female, 105 (39.3%) were of Aboriginal ancestry, and the median age at baseline was 36.5 years (interquartile range [IQR] = 29.8–43.5). The median duration of follow-up was 50.6 (IQR = 16.5–95.0) months. The median CD4 cell count at baseline was 240 (IQR = 140–360) cells/μL, while the median HIV-1 viral load was 86,000 (IQR = 36,300–120,000) copies/mL. The cumulative rate of HIV-1 RNA suppression for the entire sample was 65.2 (95% confidence interval [CI]:

Discussion

The present study demonstrates lower rates of plasma HIV-1 RNA suppression among IDU who are actively injecting at the time of ART initiation in comparison to individuals who were not injecting at this time. The effects of the various drugs (e.g., heroin vs. cocaine) on HIV-1 RNA viral suppression did not differ greatly when baseline drug use was considered. When injection drug use patterns throughout follow-up were considered in time-updated models, differences between abstinent and active

Role of funding source

This study was supported by US National Institutes of Health (NIH) Grant R01DA021525 and Canadian Institutes of Health Research (CIHR) Grants MOP-79297 and RAA-79918. T. Kerr is supported by awards from the Michael Smith Foundation for Health Research (MSFHR) and CIHR. M.-J. Milloy is supported by awards from CIHR and MSFHR. B. Marshall is supported by a research fellowship award from CIHR and an International AIDS Society/National Institute on Drug Abuse (NIDA) Fellowship in Encouraging HIV

Contributors

E. Wood had full access to all of the data in the study and takes full responsibility for the integrity of the data and the accuracy of the data analysis. T. Kerr, B. Marshall, and E. Wood designed the study and wrote the protocol. R. Zhang conducted the statistical analysis, and all authors interpreted the results. T. Kerr wrote the manuscript. E. Wood, B. Marshall, M.-J. Milloy, S. Guillemi, and J. Montaner critically revised the manuscript and contributed important intellectual content. All

Conflict of interest

J. Montaner has received educational grants from, has served as an ad hoc advisor to, or has spoken at various events sponsored by Abbott Laboratories, Agouron Pharmaceuticals Inc., Boehringer Ingelheim Pharmaceuticals Inc., Borean Pharma AS, Bristol-Myers Squibb, DuPont Pharma, Gilead Sciences, GlaxoSmithKline, Hoffmann-La Roche, Immune Response Corporation, Incyte, Janssen-Ortho Inc., Kucera Pharmaceutical Company, Merck Frosst Laboratories, Pfizer Canada Inc., Sanofi Pasteur, Shire Biochem

Acknowledgements

The authors sincerely thank the study participants for their contribution to the research, as well as current and past researchers and staff. We would specifically like to thank Deborah Graham, Tricia Collingham, Caitlin Johnston, Steve Kain, and Calvin Lai for their research and administrative assistance.

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