Poor Drug Adherence Is Less Likely to Cause Resistance

Surprising findings of a study by researchers at the University of California, San Francisco, suggest that HIV drug resistance is more likely to develop among patients who take most of their medications as prescribed and not among those whose adherence is very poor. The study, appearing in the September 5 issue of the journal AIDS, showed that resistance mutations were twice as likely to occur in patients who took 80% or more of their antiretroviral medications than in patients who took 40% or less. Previous studies have shown that adherence needs to be 95% or higher to prevent the development of drug-resistant virus. The researchers say the difference between 'good adherers' and 'bad adherers' may be due to the fact that very poor adherence does not allow enough of the anti-HIV drugs to build up in the body to either effectively combat the virus or to allow it to mutate defenses against the medications. 'Good adherence still is the best bet to prevent becoming ill or dying from HIV,' says lead study author David Bangsberg.