Injection drug users (IDUs) starting their first antiretroviral regimen in British Columbia, Canada, controlled HIV more often if they started with ritonavir-boosted atazanavir (a protease inhibitor) than with efavirenz (a nonnucleoside). The researchers call for a randomized trial of first-line regimens in IDUs.

IDUs continue to make up a sizeable proportion of HIV populations in many regions, including Eastern Europe, Central Asia, and Spain. But little research has probed for differences in response to standard antiretroviral regimens in IDUs.

Researchers in British Columbia, which has a large IDU population in Vancouver, studied 1163 HIV-positive adults who began combination antiretroviral therapy (ART) between 1 January 2000 and 28 February 2009. Follow-up continued until 28 February 2010.

Defining treatment response as a viral load below 50 copies/mL in the first 6 months of therapy, the researchers compared responses to first-line regimens based on atazanavir/ritonavir and efavirenz—antiretrovirals frequently recommended as preferred first-line choices.

Of the 1163 cohort members, 796 (68%) had a viral load below 50 copies/mL at 6 months, 32% of whom reported a history of injection drug use.

Statistical analyses considering different variables that might affect viral suppression consistently determined that atazanavir/ritonavir yielded a better response than efavirenz in IDUs. Odds ratios in these analyses ranged from 1.45-1.51 to 1.74-1.95, which the researchers characterized as “a surprisingly high benefit.”

The British Columbia team notes that most people in their study group—including those with an IDU history—can achieve viral suppression within 6 months of starting a first antiretroviral regimen. For IDUs, they conclude, atazanavir/ritonavir was “the most resilient regimen” and was more effective than efavirenz.

“Given the limited inclusion of IDUs in clinical trials of [ART]’s efficacy,” the researchers urge, “a randomized clinical trial comparing different first-line [ART] regimens among IDU[s] is warranted based on these results.”

By Mark Mascolini

Source: Viviane Dias Lima, Bohdan Nosyk, Evan Wood, Tsubasa Kozai, Wendy Zhang, Keith Chan, Julio S.G. Montaner. Assessing the effectiveness of antiretroviral regimens in cohort studies involving HIV-positive injection drug users. AIDS. 2012; 26: 1491-1500.

For the study abstract

(Downloading the complete article requires a subscription to AIDS or an online payment; the abstract is free.)