Less Than 95% Adherence to NNRTI Therapy Can Lead to Viral Suppression

David Bangsberg, associate professor of medicine at the University of California-San Francisco, analyzed HIV viral load suppression, defined as fewer than 400 copies per milliliter, in relation to treatment adherence for 110 HIV-positive adults living in San Francisco who were enrolled in the Research on Access to Care in the Homeless study from July 1996 through April 2000. Among the participants, 56 were treated with protease inhibitors -- indinavir, nelfinavir, ritonavir or saquinavir -- and 54 were treated with non-nucleoside reverse-transcriptase inhibitors -- efavirenz or nevirapine -- for an average of 9.1 months. The study, published in Clinical Infectious Diseases, finds that a majority of the reverse-transcriptase inhibitor group had suppressed viral loads if they took between 54% and 100% of their pills, while only members of the protease inhibitor group who had 95% or greater adherence achieved viral load suppression. Viral load suppression was significantly higher for the reverse-transcriptase inhibitor group than the protease inhibitor group, especially for patients with between 53% and 74% treatment adherence, the study says. Although Bangsberg writes that the study has several limitations, he concludes that the research provides "evidence that patients with moderate levels of adherence may also do well while receiving potent antiretroviral therapy" (Bangsberg, Clinical Infectious Diseases, 10/1). In a related commentary, Roy Gulick, associate professor of medicine at Weill Medical College of Cornell University, writes that the antiretroviral treatment "goal[s]" are "best accomplished with (near) perfect adherence," but recent data based on reverse-transcriptase regimens "reassure us" that current regimens "can tolerate some degree of imperfect adherence while maintaining the beneficial effects of HIV therapy in most patients" (Gulick, Clinical Infectious Diseases, 10/1).

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