Abstract

Concerns regarding metabolic perturbations occurring during protease inhibitor (PI)-based regimens have led to investigation of switching from a PI-based to a non-nucleoside reverse transcriptase inhibitor- or abacavir-based regimen. There appear to be considerable benefits to switching from a PI-based regimen to one of these PI-sparing regimens. In particular, patients appear generally pleased with the improved administration characteristics of the new regimens, and improvements in quality of life have been reported. However, resolution of the metabolic abnormalities that may arise during PI therapy is incomplete. Peripheral or subcutaneous fat mass improvements are not evident in the studies reported to date. Weight gain, probably in part due to removal of PI-related dietary restrictions, has been observed and may lead to improvements in appearance. Maintenance of virologic control varies among studies but is generally in the range of 85% to 100% of the patients receiving the PI-sparing regimen. The extent of prior drug exposure (or drug resistance) in patients entering the studies may be a key risk factor for loss of virologic control.