Low plasma concentrations of indinavir are related to virological treatment failure in HIV-1-infected patients on indinavir-containing triple therapy.

All human immunodeficiency virus type 1 (HIV-1)-infected patients who started to use indinavir (800 mg three times a day) as part of their triple drug regimen were included in a study to determine the importance of low plasma concentrations of indinavir as a cause of virological treatment failure. The indinavir concentration and a number of patient characteristics at baseline were tested as risk factors for virological treatment failure (defined as a viral load above 200 copies/ml after 24 weeks of treatment) in univariate and multivariate analyses; 65 patients were included. Virological treatment failure occurred in 36.9% of the patients. Multivariate analysis showed that a low plasma concentration of indinavir (odds ratio 0.1), a high viral load at baseline (odds ratio 2.6) and pretreatment with another protease inhibitor (odds ratio 10.0) were independent factors related to virological treatment failure. Monitoring of indinavir plasma concentrations may be an important tool for the optimization of triple drug combination therapy.