Treatment failure may take up to 90 days after patients stop taking their antiretroviral medication as directed
Research Activities, May 2009, No. 345
For treatment to succeed, patients with HIV infection must strictly adhere to their highly active antiretroviral therapy (HAART). If they do not, treatment failure (also called virological failure) occurs, which means that HIV increases in the blood to detectable levels and often it is a resistant strain that is harder to treat. A new study finds that the window between when patients stop adhering to an efavirenz-based HAART regimen and onset of virological failure can be as long as 90 days. This presents a window of opportunity for clinicians to take action as soon as nonadherence is detected, to prevent virological failure and maintain HIV suppression, suggest the study authors.
Investigators from the Center for Education and Research on Therapeutics (CERT) at the University of Pennsylvania School of Medicine and colleagues observed 116 adults with HIV infection with virological suppression (undetectable HIV RNA in the blood) on efavirenz-based HAART. Patients were seen each month and the study was stopped either at virological failure (more than 1,000 copies of HIV RNA/mL of blood) or 12 months, whichever came first. They used a monitoring system to measure the percentage of HAART doses taken during the study period. The results were summarized in four 90-day adherence periods: immediately, 30 days, 60 days, or 90 days prior to virological failure.
HAART adherence was significantly lower for the seven patients with virological failure compared with the other 109 without virological failure. These differences were significant even up to 90 days prior to the virological failure date (57 percent adherence in the failure group vs. 95 percent in the nonfailure group). The study demonstrates the flaw in assuming that all HIV patients with undetectable viral loads are adherent and therefore should be encouraged to "keep doing what you're doing." It would be better for clinicians to either directly ask HIV patients with an undetectable viral load about their drug adherence or assess pharmacy refills or both with every clinic visit.
The study was supported in part by the Agency for Healthcare Research and Quality (HS10399). For more information on the CERTs program, please visit http://certs.hhs.gov/.
More details are in "How long is the window of opportunity between adherence failure and virologic failure on efavirenz-based HAART?" by Robert Gross, M.D., M.S.C.E., Warren B. Bilker, Ph.D., Hao Wang, Ph.D., and Jennifer Chapman, M.D., in the May-June 2008 HIV Clinical Trials 9(3), pp. 202-206.