Factors related to virologic failure among HIV-positive injecting drug users treated with combination antiretroviral therapy including two nucleoside reverse transcriptase inhibitors and nevirapine.

Treatment strategies in human immunodeficiency virus (HIV)-positive active injecting drug users (IDUs) must take into account their lifestyles, that often result in low adherence to therapy. The nonnucleoside reverse transcriptase inhibitors (NNRTI) offer simpler treatment regimens, but the appearance of drug resistance during treatment failure may cause high levels of cross-resistance to all NNRTIs. We adopted a combination therapy of two NRTIs and nevirapine (NVP) for treatment of IDU patients to evaluate its feasibility in such patients. From October 1998 to December 1999, demographic, clinical, and laboratory data from 80 IDUs on this regimen were collected. Fisher's exact test, Kaplan Meier method, and Cox model were used for statistical analysis. Overall, 20 IDUs discontinued the treatment because of side effects and 20 IDUs experienced treatment failure. Considering the treatment failure as an end point, 55.6% (95% confidence interval [CI]: 37.9%-72.6%) of patients was still undergoing treatment after 12 months compared to 44.6% (31.8%-58.6%) when discontinuation was also taken into account. An increasing trend over time was observed in the CD4+ lymphocyte count, among failing and nonfailing IDUs. By multivariate analysis, baseline HIV-RNA, treatment breaks and low adherence and active injecting drug use turned out to be significantly associated with treatment failure. Our results show that continuing injecting drug use and treatment breaks are the main factors that can lead to treatment failure in IDUs and easily to NNRTI class resistance.