Antiretroviral adherence and HIV treatment outcomes among HIV/HCV co-infected injection drug users: the role of methadone maintenance therapy

OBJECTIVE: We examined the association of methadone maintenance therapy (MMT) with highly active antiretroviral therapy (HAART) adherence and HIV treatment outcomes among a cohort of HIV/HCV co-infected injection drug users (IDUs). METHODS: We obtained demographic, drug use, and addiction care history from the Vancouver Injection Drug User Study (VIDUS), which is an open cohort study of IDUs. The questionnaires were longitudinally linked to the British Columbia HIV/AIDS Drug Treatment Program to obtain HAART adherence and HIV treatment outcome data. There were 278 VIDUS participants who accessed HAART from August 1, 1996 to November 24, 2003. We constructed longitudinal logistic models using generalized estimating equations to examine the independent associations between methadone maintenance therapy and the following outcomes: HAART adherence; plasma HIV-1 RNA suppression; and CD4 cell rise of 100cells/mm(3). RESULTS: Among participants who reported at least weekly heroin use, MMT was independently associated with lower odds of subsequent weekly heroin use during the follow-up period (adjusted odds ratio; 95% confidence interval [AOR; 95% CI]: 0.24; 0.14-0.40). We also found that MMT was positively associated with adherence (AOR 1.52; 95% CI 1.16-2.00), HIV-1 RNA suppression (AOR 1.34; 95% CI 1.00-1.79), and CD4 cell count rise (AOR 1.58; 95% CI 1.26-1.99). CONCLUSIONS: Among HIV/HCV co-infected IDUs on HAART, enrollment in MMT was associated with reduced heroin use, and improved adherence, HIV-1 RNA suppression and CD4 cell count response. Integrating opiate addiction care and HIV care may provide improved health outcomes for this vulnerable population and should be further explored.