Study Shows Newer, More Powerful HIV Therapy May be Effective Even When Some Doses Are Missed

For years, it has been thought that HIV antiretroviral therapy was successful only for those who took every dose on time. But a new study shows that while compliance is still important, today's more-potent forms of therapy can be effective even for those who fall short of perfect adherence--which means that drug users, the homeless, the mentally ill, and other vulnerable groups who were considered unlikely to take every dose on time may fully benefit from therapy. The research is published in the Oct. 1 issue of Clinical Infectious Diseases, now available online.

When first developed in the mid-1990s, antiretroviral therapy might require a patient to take up to 20 pills a day, some taken every eight hours, with strict food requirements. An often-cited study in 2000 showed that patients needed to follow the regimen at least 95 percent of the time to achieve the desired virologic suppression and recovery of the immune system.

However, that study's findings were based upon patients receiving regimens that only partially suppress the virus and are now outdated, including an un-boosted protease inhibitor and two nucleoside analogs. More potent non-nucleoside reverse transcriptase inhibitors (NNRTI) regimens were later developed and led to greater overall rates of viral suppression.

In the new study, David Bangsberg, MD, MPH, of the University of California, San Francisco, and colleagues found that patients on NNRTI regimens were achieving the same rates of viral suppression with a lower level of adherence to the schedule. "We found that adherence is very closely related to viral suppression," said Bansgberg, "but more-recent potent therapy can lead to better suppression at moderate levels of adherence."

In practice, many clinicians have held fast to the 95 percent adherence "policy" and did not recommend treatment for patients such as drug users, the homeless, or the mentally ill, who were considered unable to meet this 95 percent mark largely because of fears of developing drug resistance. In the absence of treatment, HIV disease progressed and many people died of AIDS.  This new study shows that the window of adherence is open a bit wider. "Patients who might miss that 95 percent mark are still likely to benefit from treatment," said Bangsberg.

Bangsberg stresses that the results of this study should not be used as an excuse for patients not to take their pills: "Every missed pill increases the chance of virologic failure. It's a continuous relationship," he said. "The higher the level of adherence, the better the chance of full and sustained virologic suppression. The more you can adhere, the better you'll suppress your virus."

Source: Infectious Diseases Society of America (IDSA)