A study (ACTG 5097) was designed to determine whether higher levels of efavirenz in the blood are related to side effects of the central nervous system (CNS). CNS side effects, including vivid nightmares, difficulty sleeping and mood changes have been reported in a number of efavirenz studies. Results of ACTG 5097s were recently reported, finding a significant association between genetic factors, race and how quickly efavirenz is cleared from the bloodstream.
ACTG 5097s found that people who identified as black or Hispanic maintained higher blood levels of efavirenz than their white non-Hispanic counterparts. As might be expected, people with higher blood levels of the drug were more likely to stop taking it due to side effects. The study also found that while people with higher efavirenz blood levels did not develop CNS side effects more rapidly than those with lower blood levels, they were more likely to stop taking efavirenz because of them. This suggests that while CNS effects aren't developing more rapidly among people with higher blood levels of drug, when they do occur they are more severe.
Upon closer examination, researchers found a genetic variation that explained the difference in how people's bodies processed efavirenz better than racial identification. This genetic variation, which affects how the liver functions, was found in 20% of black participants and only 3% of white participants. No data were presented regarding the percentage of Hispanic study participants who carry the gene. The genetic tests used in this study are unlikely to be available anytime soon. In the absence of access to these tests, Blacks and Hispanics who are taking efavirenz should be aware of a potential increased risk of side effects and continue careful monitoring.
Back to the Project Inform Perspective July 2004 contents page.