Protease-inhibitor boosting in the treatment-experienced patient

Highly active antiretroviral therapy (HAART) consisting of protease inhibitor (PI)-containing regimens has revolutionized the treatment options for HIV-infected individuals. However, even with successful treatment, virus is not completely eliminated, and virologic failure can occur because of treatment complexity, tolerability and side-effect issues, and suboptimal pharmacokinetics. Ritonavir-boosted PI therapies (i.e. combinations of low-dose ritonavir with a primary PI) can effectively enhance the pharmacokinetics of the primary PI by reducing its first-pass metabolism and postabsorptive clearance, thereby increasing potency. Boosted PI regimens may also simplify treatment by reducing regimen complexity and pill burden. For treatment-experienced patients, the higher PI concentrations achieved with ritonavir boosting may improve activity against PI-resistant virus. This article reviews the principles of PI boosting, its advantages and disadvantages, and the clinical experience with this strategy in treatment-experienced populations.