Indinavir plasma concentrations and resistance mutations in patients experiencing early virological failure.

Virological failure under protease inhibitor (PI)-based antiretroviral regimens is often not explained by the selection of resistance mutations. The role of low indinavir (IDV) plasma levels in treatment failure was assessed in 46 subjects experiencing early virological failure to a first-line IDV-containing triple combination. Overall, 69% of patients showed subtherapeutic IDV plasma levels (it was not detected at all in 75% of them). Subjects with detectable but suboptimal IDV levels developed more IDV resistance mutations. Thus, drug monitoring may be useful to assess treatment adherence and risk of drug resistance in early virological failures. This information may be crucial for choosing the most appropriate rescue intervention.