An updated version of the United States Department of Health and Human Services’ (DHHS) Guidelines for the use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents was published online today and contains some important changes to the lineup of antiretroviral drugs recommended for use by people beginning HIV treatment for the first time.

The guidelines continue to recommend combining either a protease inhibitor (PI) or a non-nucleoside reverse transcriptase inhibitor (NNRTI) with a backbone of two nucleoside reverse transcriptase inhibitors (NRTIs), and they maintain lists of either “preferred” or “alternative” drugs that may be combined to form a complete regimen for first-time treatment takers.

The dual-NRTI combination zidovudine (Retrovir) and lamivudine (Epivir)—often used together as the one-pill, twice-daily tablet Combivir—has been moved from the “preferred” to the “alternative” category in the new guidelines. In place of Combivir, the guidelines’ authors promote the dual-NRTI combination abacavir (Ziagen) and lamivudine—frequently prescribed as Epzicom, a one-pill, once-daily tablet—to be a preferred option, provided that a person first takes a test to determine whether or not they have the gene (HLA-B5701) that can greatly increase the risk of a serious allergic reaction to abacavir.

In terms of PIs, the new guidelines now list saquinavir (Invirase) combined with ritonavir (Norvir) as part of the “alternative” list—previously, this combination was classified as inferior to both preferred and alternative PI options. And while lopinavir/ritonavir (Kaletra) remains approved by the U.S. Food and Drug Administration (FDA) for either once-daily or twice-daily use, the new guidelines note that once-daily administration may not be potent enough for people starting HIV treatment with viral loads exceeding 100,000.

Additional changes to the guidelines include the demoting of the PI nelfinavir (Viracept) and the dual-NRTI combination stavudine (Zerit) plus lamivudine. These antiretrovirals are no longer recommended as components for initial HIV therapy.