With the advent of highly active antiretroviral therapy (HAART), it was hypothesized that its consistent use could lead to a cure for HIV infection in as little as three years [Perelson, 1997]. Subsequent research has shown this model to be incorrect [Finzi, 1999]. In addition, long term use of HAART has now been associated with significant metabolic abnormalities, which could lead to unintended morbidity, possibly worse than what one could expect from the progression of untreated HIV-associated immune disease over the same period of time [Carr, 2000]. Accordingly, current recommendations for antiretroviral therapy have become more conservative. It is now suggested that a person with a CD4 count > 350 cells/mm³ may safely delay initiation of HAART [Yeni, 2002].However, for those who still require HAART, the risks of short-term and long-term toxicities remain, even if full virologic suppression is achieved. In this setting, a number of switching strategies have been evaluated (Negredo et al, 2002 & Martinez et al, 2003), mostly involving single drug substitutions of a protease inhibitor (PI) for a non-nucleoside agent (NNRTI) or abacavir (ABC). In general terms, these hae shown that virologic suppression is usually maintained, with improvement in drug-related side effects, including metabolic toxicities. A number of patients who are currently taking effective HAART are experiencing side effects to one or more of the agents in their regimen that is not severe enough to mandate an immediate change in their regimen, but that is having a measurable effect on their qualify of life. Over time, these effects may have an impact on adherence to therapy and its long-term efficacy. Given the recent availability of ATV (+/-RTV), its once daily administration, low pill count and favourable side effect profile, it is being used in clinical practice as part of single drug substitution strategies in patients exhibiting a maximal response to HAART. There is a clear need to examine this practice in a systematic manner to document its occurrence, efficacy and safety.
We hypothesize that, in patients with maximal virologic suppression on a double class regimen (including two NRTIs and an NNRTI or a PI, boosted with RTV or not), and in whom a decision has been made to implement a single drug substitution of the NNRTI or PI for ATV (+/-), this will lead to an improvement in objectively measured quality of life without any negative impact on the virologic efficacy of the regimen.