The causal effect of opioid substitution treatment on HAART medication refill adherence

Abstract

Background People who inject drugs (PWID) account for roughly 13% of the prevalent HIV/AIDS population outside of sub-Saharan Africa, and access to opioid substitution treatment (OST) is limited in many settings globally. OST likely facilitates access to HAART, yet sparse evidence is available to support this hypothesis. Our objective was to determine the causal impact of OST exposure on HAART adherence among HIV-positive PWID in a Canadian setting. Methods We executed a retrospective cohort study using linked population-level data for British Columbia, Canada (January 1996–March 2010). We considered HIV-positive PWID after meeting HAART initiation criteria. A marginal structural model was estimated on a monthly timescale using inverse probability of treatment weights. The primary outcome was 95% HAART adherence, according to pharmacy refill compliance. Exposure to OST was defined as 95% of OST receipt, and we controlled for a range of fixed and time-varying covariates. Results Our study included 1852 (63.3%) HIV-positive PWID with a median follow-up of 5.5 years; 34% were female and 39% had previously accessed OST. The baseline covariate-adjusted odds of HAART adherence following OST exposure was 1.96 (95% confidence interval: 1.72–2.24), although the adjusted odds estimated within the marginal structural model was 1.68 (1.48–1.92). Findings were robust to sensitivity analyses on model specification. Conclusion In a setting characterized by universal healthcare and widespread access to both office-based OST and HAART, OST substantially increased the odds of HAART adherence. This underlines the need to address barriers to OST globally to reduce the disease burden of both opioid dependence and HIV/AIDS.

Methadone maintenance therapy and viral suppression among HIV-infected opioid users: The impacts of crack and injection cocaine use

“…There is growing evidence indicating that HIV-positive opioid dependent individuals enrolled in OST have superior HIV/AIDS treatment outcomes, including improved rates of VL suppression (Altice et al, 2011; Lappalainen et al, 2015; Nosyk et al, 2015a; Nosyk et al, 2015b; Wood et al, 2005). It has been hypothesized that this may be due to the stabilization afforded by reduced opioid use and dependence symptoms (e.g., drug withdrawal and craving) and reduced time and effort in procuring opioids (e.g., through involvement in drug scenes and illegal income generation activities), as well as increased contact with healthcare systems (Nosyk et al, 2015a; Palepu et al, 2006).…”

“…It has been hypothesized that this may be due to the stabilization afforded by reduced opioid use and dependence symptoms (e.g., drug withdrawal and craving) and reduced time and effort in procuring opioids (e.g., through involvement in drug scenes and illegal income generation activities), as well as increased contact with healthcare systems (Nosyk et al, 2015a; Palepu et al, 2006). Yet there is limited and conflicting evidence regarding whether the positive impact of OST on HIV-treatment outcomes are similarly observed among dual opioid/cocaine-dependent individuals.…”

“…Despite these challenges, recent studies have documented improved HIV-related outcomes among opioid-dependent individuals enrolled in opioid substitution treatment (OST) programs, including increased access to and adherence to ART, and decreased HIV incidence (Ahamad et al, 2015; Altice et al, 2011; Lappalainen et al, 2015; Nosyk et al, 2015a; Palepu et al, 2006; Wood et al, 2005). While the potential of OST as a platform to facilitate engagement of PWUD in HIV care is encouraging, the extent to which these benefits are sustained in the context of ongoing cocaine use is unclear.…”

Antiretroviral Drugs for Treatment and Prevention of HIV Infection in Adults

“…Opioid substitution therapy for opioid-dependent patients improves retention in care and is recommended (evidence rating AIIa). 149 Depression is associated with poor adherence, and routine screening for depression is recommended (evidence rating AIII). 110,134 Depression treatment improved ART adherence 150 and HIV outcomes 151 ; however, 3 US-based randomized clinical trials of antidepressant treatment showed no effect on ART adherence.…”

High-intensity cannabis use and HIV clinical outcomes among HIV-positive people who use illicit drugs in Vancouver, Canada

“…This led to the establishment of a variety of innovative harm reduction programs, including needle and syringe distribution (Werb et al, 2013), supervised injection (Wood et al, 2004), and opioid substitution programs (Nosyk et al, 2015). In 2006, the Vancouver Police Department announced a de facto policy of cannabis use decriminalization in an effort to shift focus towards illicit drug manufacturing and distribution rather than personal use (The Vancouver Province, 2006).…”