People taking a regimen including Sustiva (efavirenz) appeared to have greater limb fat loss and gut fat accumulation than those on Kaletra (liponavir/ritonavir)–based regimen, according to a study presented at the Fifth International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention in Cape Town.

A recently published study—AIDS Clinical Trials Group (ACTG) 1542—found that there was a higher rate of limb fat loss (lipoatrophy) in those on Sustiva than those on Kaletra. However, more people in that study were also on the drugs Zerit (stavudine) and Retrovir (zidovudine), which are most notorious for causing lipoatrophy.

To determine whether the offending drugs were the primary cause of the earlier finding about Sustiva, Jan Van Lunzen, MD, from the University Medical Center Hamburg-Eppendorf, in Germany, and his colleagues studied the medical records of 322 HIV-positive patients in their study. The patients received either Sustiva with two newer nuclesos(t)ide reverse transcriptase inhibitors (NRTIs) or Kaletra with two of the newer NRTIs. The most popular NRTI combination was Viread (tenofovir) with Emtriva (emtricitabine) or Epivir (lamivudine). The second most popular combination was Ziagen (abacavir) with Epivir. The average length of time on the study was 3.5 years.

Van Lunzen’s team found no differences in the efficacy and safety of the two compared drug regimens. They did find, however, that people taking Kaletra had greater elevations in triglycerides. Also, echoing the earlier study, people taking Sustiva had both more loss of limb fat and more gains of fat in their guts.

The authors acknowledge that controlled studies—in which people are randomized and followed without knowing what medications they are taking—would more rigorously determine whether their findings are legitimate or a product of chance or other factors. More objective methods, such as dual energy X-ray absorptiometry (DEXA) scans, for measuring changes in limb fat and fat accumulation in the waist and breasts would also be helpful.