The recent development of once-daily antiretroviral agents and fixed-dose combination formulations has been an important development in antiretroviral regimen simplification. Recent studies indicate that once-daily antiretroviral regimens improve adherence, especially in antiretroviral-naïve patients and in difficult-to-treat populations, such as the homeless or marginally housed. However, there are potential risks with the higher peak and lower trough plasma drug concentrations that may result from certain once-daily formulations. Due to the multifactorial and complex nature of adherence behavior, clinicians' efforts to improve patient adherence should not be limited to prescribing once-daily regimens, but should also consider social support, side effect management, and adherence support tools, such as pillbox organizers and other targeted interventions. Additional research will clarify the benefits of once-daily and fixed-dose combination regimens on clinical and virologic outcomes. Comprehensive cost-benefit analysis of regimen simplification could help facilitate evidence-based decisions regarding antiretroviral regimen choices.
Keywords: fixed-dose combination; health care costs; once-daily antiretroviral drugs; regimen adherence; regimen simplification.