The HIV drug efavirenz (found in Sustiva and Atripla) does not substantially worsen psychiatric side effects of interferon, a treatment for hepatitis C virus (HCV), according to a study published online July 23 in the Journal of Acquired Immune Deficiency Syndromes.

Interferon is known to cause depression in as many as 50 percent of people who use it to treat HCV. Likewise, the HIV drug efavirenz can cause a variety of central nervous system side effects. Physicians have therefore been concerned that combining both treatments in their patients who are coinfected with both HIV and HCV may put them at a higher risk for depression and other psychiatric side effects.

Carmen Quereda, MD, and her colleagues from the Hospital Ramón y Cajal in Madrid, enrolled 266 HIV- and HCV-coinfected patients to investigate the psychiatric side effects of the two treatments combined. Fifty-three patients received both efavirenz and interferon, and 216 received interferon with other HIV antiretroviral (ARV) drugs.

Dr. Quereda’s team found that neurological and psychiatric side effects occurred in up to 80 percent of patients in both groups. People taking both drugs did have more symptoms of mood disorders than people not taking efavirenz; however, the difference was not statistically significant—it could have occurred by chance. Also, there was no meaningful difference between the groups in terms of the number of people who suffered serious depression that required antidepressant medication or in the number of people who had to discontinue HCV treatment.