When to switch and what to switch to: strategic use of antiretroviral therapy.

Clinical cohort studies suggest that as many as 60% of patients experience virologic failure of a first-line antiretroviral regimen. Second-line and rescue (or salvage) regimens have a poorer success record: Most studies presented to date show a short-term virologic response rate of only approximately 30% in treatment-experienced individuals. That rate will improve with better understanding of what causes initial virologic failure, continued development of new antiretroviral agents (including drugs with new mechanisms of action) and new treatment strategies (including dual-protease inhibitor regimens), and more widespread use of resistance testing. Further clinical research is needed to improve salvage options, and physicians should consider enrolling treatment-experienced patients in clinical trials.