HIV-positive injecting drug users fail to derive the same virological benefit from HAART as either HIV-positive former intravenous drug (IV) users or people with HIV who have never injected drugs according to a Canadian study published in the April 15th edition of the Journal of Acquired Immune Deficiency Syndromes.
There are conflicting data on the success of HAART in injecting drug users, and investigators in British Columbia compared the proportion of current IV drug users who achieved two successive viral load load results below 500 copies/ml after starting HAART. Patients were recruited between 1996 and 2000 and were followed-up until Spring 2002.
A total of 578 patients participated in the study. Data on CD4 cell count and HIV viral load were obtained and participants were asked to complete a questionnaire concerning their demographic details and drug-taking risk behaviour. To establish levels of adherence, investigators obtained information on the number of prescriptions being refilled.
Current IV drug use was reported by 78 (13%)of patients, a further 96 (17%) said they had used IV drugs and 404 (70%) said they had never used IV drugs.
Adherence was worst in current IV drug users (77%), followed by former users (81.5%) and people who had never used drugs (91.6%). Although not noted by the investigators, none of the groups achieved the minimum 95% adherence which has been associated with the best response to HAART.
Univariate analysis found that current and former drug users were less likely to achieve an undetectable viral load. Other factors associated with a poor virological response were a higher baseline viral load (170,000 copies/ml versus 120,000 copies/ml), receiving fewer months of therapy (14.5 versus 39), had average adherence of only 60% versus 100%, and were more likely to be taking an NNRTI based regimen.
In multivariate analysis current drug users were still found to be less likely than people who had never injected drugs to achieve viral suppression, although this was no longer the case for former users.
Factors associated with achieving two successive viral load results below 500 copies/ml were adherence, lower baseline viral load, and, in a reversal of the univariate analysis, NNRTI-based therapy.
Regarding adherence, the investigators note that using prescription refill as a measure is unsatisfactory as patients in their study were obtaining medication but then failing to take it.
The investigators conclude that when other prognostic variables were controlled for, current IV drug users were less likely to achieve a virological response to HAART. High adherence, longer duration of therapy, lower baseline viral load and NNRTI-based therapy were also associated with “superior virologic outcome for former and non-injection drug users.”
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Palepu A et al. Impaired virologic response to highly active antiretroviral therapy associated with ongoing injection drug use. JAIDS 32: 522 - 526, 2003.