AIDSWEEKLY Plus; Monday, September 8, 2003
Staff Medical Writers

"These findings will make us rethink the argument that life-saving antiretroviral drugs should be denied to some populations because poor pill-taking behavior might accelerate the creation of resistant mutations of the HIV virus," said the study's lead author, David R. Bangsberg, MD, MPH, director of the UCSF Epidemiology and Prevention Interventions (EPI) Center at San Francisco General Hospital Medical Center (SFGHMC).

In a study of patients on antiretroviral drugs, resistance mutations were twice as likely to occur in patients who took 80% or more of their antiretroviral medications as they were in patients who took 40% or less, according to the researchers.

"Ironically it is the 'good adherers' who developed more resistance, rather than the 'problem patients'," said study co-investigator Andrew Moss, PhD, professor of epidemiology and medicine.

"You need pressure from antiviral medications for resistance to develop. What is surprising is that what we typically take to be excellent pill-taking - 80% of pills or better - leads to more resistance than occasional or inconsistent pill-taking. A caveat - this does not mean patients should take less of their drugs to avoid creating resistance. Good adherence to the antiviral regimens still is the best bet to prevent becoming ill or dying with HIV/AIDS. Many patients with excellent, even perfect, pill-taking are living longer with resistant virus, than those who do not take enough medication to select for resistant virus," said Bangsberg.

The study, appearing in the September 5, 2003, issue of AIDS, looked at 148 participants from the Research on Access to Care in the Homeless (REACH) cohort, a systematic sample of HIV-positive adults recruited from homeless shelters, free meal programs, and low-income single-room-occupancy hotels in San Francisco. The participants, who consented to unannounced pill counts to measure adherence, were all on anti-HIV regimens taking three or more antiretrovirals.

Pill counts were conducted, unannounced, every 3-6 weeks over a 12-month period at the participant's usual place of residence. Blood was drawn monthly and tested for levels of HIV virus. Blood specimens were also analyzed for drug-resistant mutations using genotype tests.

Participants in the top two quintiles of adherence, who took 80% or more of their medications, accounted for more than half of all new drug resistance mutations occurring in the study. Those in the next two quintiles, who took between 42% and 78% of their medications, had 35% of the new mutations. Only 12% of the new drug resistance mutations were found in the participants in the lowest adherence quintile, those who took less than 41% of their medications.

This article was prepared by AIDS Weekly editors from staff and other reports.

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