POZ - Treatment News : Treatment Adherence: Better Is Best

Near perfect adherence remains a leading predictor of treatment success, according to a Canadian study published in the November 12 issue of AIDS and reported by aidsmap. According to the newest data, people who miss more than 5 percent of their antiretroviral (ARV) doses—no more than one dose a month if using once-daily medications—were much more likely to experience treatment failure.

In the early days of combination ARV treatment, studies suggested that scrupulous adherence was necessary to keep HIV fully suppressed and to avoid developing drug resistance. As treatments have gotten both more potent and easier to use, however, there have been hopes that less stringent adherence would be necessary.

To determine the impact of adherence on treatment success using modern-day regimens, Viviane Lima, PhD, from the British Columbia Centre for Excellence in HIV/AIDS in Vancouver, Canada, and her colleagues studied 878 HIV-positive patients who started ARV therapy for the first time between January 2000 and November 2004. The majority of patients were men, 28 percent had a history of injection drug use and 17 percent had an AIDS diagnosis at the time of treatment initiation. Most people started treatment with a protease inhibitor (PI) boosted with low-dose Norvir (ritonavir) or a non-nucleoside reverse transcriptase inhibitor (NNRTI).

Lima and her colleagues found that 63 percent of people with greater than 95 percent adherence—which equals only one missed dose per month for people on once-daily regimens and only three missed doses per month for people on twice-daily regimens—had good responses to treatment, with CD4 counts increasing by at least 145 cells and undetectable HIV levels for most of the follow-up period. Conversely, 41 percent of people who took their meds correctly 80 to 95 percent of the time had the best treatment response. People who missed more than 20 percent of their doses had less than an 11 percent chance of treatment success.

The authors acknowledge that their measure of adherence was not the strictest possible—they calculated pharmacy refills during the first year of treatment year. Lima and her colleagues point out, however, that their definition of treatment success is more rigorous and has longer follow-up than many other studies, meaning that it may provide a more accurate assessment of the impact of adherence on treatment success.