Purpose of review: The inhibitory quotient of boosted protease inhibitors is a measurement incorporating both plasma drug exposure and resistance testing. Inhibitory quotients have been assessed in over 50 clinical studies to date, many of these studies describe highly significant associations between the inhibitory quotient and virological outcomes. This review will focus on studies that assess the inhibitory quotient in a prospective fashion and with the use of newly available boosted protease inhibitors.
Recent findings: Atazanavir, darunavir and tipranavir are the three most recently licensed protease inhibitors. Studies have described associations between the inhibitory quotient and outcomes for all of these agents with cutoff inhibitory quotient values now proposed for all of these protease inhibitors.
A prospective study has assessed the use of inhibitory quotient across many different protease inhibitor regimens and although no overall benefit was described, improved clinical outcomes were observed in specific patient groups.
Summary: Although ongoing challenges need to be overcome, recent studies have described associations between this useful parameter and modern day antiretroviral regimens.