Introduction to initial therapy for HIV infection in adults

For the initial treatment of HIV infection, a 3-drug regimen is commonly used. However, patients who do not have a high viral load, hepatitis B virus co-infection or resistance to any antivirals may be eligible for a 2-drug regimenCahn 2019Radford 2019Shu 2021. An integrase strand transfer inhibitor (INSTI)–based regimen is preferred for initial antiretroviral therapy in most situations.

Before starting antiretroviral therapy:

• ensure opportunistic infections are excluded and that appropriate screening for specific organisms occurs – see Appropriate tests to perform before starting antiretroviral therapy in Australia
• test for genotypic resistance for HIV – if treatment needs to be started before the result has returned, use a 3-drug regimen. If antiretroviral drug resistance is detected, seek expert advice.

Single-tablet once-daily combination products containing the complete antiretroviral regimen (2 or 3 drugs) improve adherenceKryst 2015Messiaen 2013. When prescribing antiretroviral combination products, carefully check the product (including ingredients and strengths), practice points for safe prescribing, and whether drug interactions are possible.

Patients with HIV and hepatitis B virus co-infection require specific regimens, see Initial therapy for adults with HIV and hepatitis B virus co-infection.

For initial antiretroviral therapy for patients with HIV infection who do not have hepatitis B virus, see:

• INSTI-based therapy
• Protease inhibitor-based therapy
• NRTI+NNRTI-based therapy¹.

For other antiretroviral regimens used for initial therapy, and for a detailed discussion about the relative merits of various drug combinations, see the guidelines listed in Australian and international HIV guidelines.