Virologic and immunologic response to regimens containing nevirapine or efavirenz in combination with 2 nucleoside analogues in the Italian Cohort Naive Antiretrovirals (I.Co.N.A.) study.

This nonrandomized study compared the virologic and immunologic responses to potent regimens containing either efavirenz or nevirapine after considering potential systematic differences between patients receiving these drugs. Virologic failure was defined as the first of 2 consecutive measurements of virus load >500 human immunodeficiency virus RNA copies/mL. Of the 694 patients included in the analysis, 460 (66.3%) started nevirapine and 234 (33.7%) started efavirenz. The adjusted relative hazard of virologic failure for patients who started nevirapine, compared with those who started efavirenz, was 2.08 (95% confidence interval, 1.37-3.15; P=.0006). In addition, patients receiving efavirenz tended to recover 5 CD4 cells/microL more per quarter (P=.05). Although comparisons of drug efficacy in nonrandomized studies should be viewed with caution, no results from randomized controlled comparisons of these drugs are thought to be available. The findings of this study are in agreement with those of other observational studies.