Structured treatment interruption refers to planned ‘drug holidays’ or breaks from treatment. While some early studies suggested that structured treatment interruption might be safe, more recent data have shown that it can be a risky strategy. In the large SMART study, for example, patients stopped therapy when their CD4 cell count was above 350 cells/mm³ and started again when it fell below this level^[1]. The study was halted prematurely after it became apparent that people who interrupted treatment not only had a higher risk of progression to AIDS-related illnesses or death - as might be expected, since they spent more time with lower CD4 counts - but also were more likely to develop heart, liver and kidney problems.

But other studies have not seen the same effect. A different strategy, in which people start and stop treatment on a fixed schedule (for example, two months on and two months off) seems to work for some patients^[2]. Further, people who started treatment ‘too soon’ - that is, with a higher CD4 cell count and lower viral load than the cut-offs recommended in current treatment guidelines - may be able to safely go off therapy until they start to experience disease progression^[3] [4].

At this time, structured treatment interruption is controversial and much remains to be learned, though the strategy is falling out of favour due to clear risks and minimal benefits^[5][6]. For further information on this strategy, see Interrupting HIV treatment.