More evidence has arrived suggesting that treating hepatitis C (HCV) before HIV is a good idea, when possible. As reported in the Journal of Infectious Diseases, researchers have found that people coinfected with HIV and HCV had fewer side effects to their HIV medicines if they successfully treated HCV first.

In the study of 132 coinfected patients in Spain, researchers first attempted to treat participants’ HCV with standard interferon-based therapy. Treatment success was defined as having undetectable HCV levels for at least six months following the end of the treatment, and 33 percent of those treated achieved this goal. Researchers then initiated HIV treatment in all study participants. Those who’d been successfully treated for HCV had far less liver toxicity from their HIV drugs than those who’d not been successfully treated for HCV prior to commencing treatment.

The study’s authors concede, however, that delaying HIV treatment is often not possible—because many people learn of their HIV status only after their immune systems have become sufficiently damaged to warrant immediate HIV treatment.