Once-daily antiretroviral (ARV) regimens are better than twice-daily regimens in both adherence and viral suppression for people new to treatment, according to a study published in the February 15 issue of Clinical Infectious Diseases and reported by aidsmap.com.

A number of studies comparing once- and twice-daily regimens have been conducted, but results have been inconsistent. To determine the impact of once-daily regimens on adherence, Jean-Jacques Parienti, MD, from the Côte de Nacre University Hospital, in Caen, France, and his colleagues analyzed the results of 11 such studies including more than 3,000 patients. Most of the studies compared twice-daily treatments to once-daily regimens commonly used today in the United States, such as once-daily Kaletra (lopinavir plus ritonavir) combined with Truvada (tenofovir plus emtricitabine) or Sustiva (efavirenz) combined with Truvada. Other once-daily regimens examined included drugs less commonly used in the developed world, such as Zerit (stavudine).

Parienti’s team found that once-daily regimens improved both adherence and suppression of HIV by nearly 5 percent in people who had never taken ARV therapy before. The result was statistically significant, meaning that it was too large to have occurred by chance. There was a trend toward improved adherence with once-daily regimens in people who were treatment experienced, but the result was not statistically significant.

The authors state that treatment-experienced patients probably failed to show a benefit from once-daily regimens due to the fact that, when they switched to once-daily from twice-daily treatment, they already had undetectable viral loads. This means that they were likely already adhering well to therapy, making it difficult to show a benefit. The modest improvements in adherence found in this analysis, however, led the authors to urge researchers to focus not only on developing once-daily medications but studying new drugs’ potency and tolerability.