Use of tenofovir and abacavir for initial and subsequent regimens in HIV treatment. Tenofovir disoproxil fumarate (TDF) or tenofovir alafenamide (TAF) + lamivudine (3TC) or emtricitabine (FTC) is the preferred nucleoside reverse transcriptase inhibitor (NRTI) backbone for initial and subsequent ART in adults, adolescents and children > 30 kg. This includes individuals previously treated with or exposed to tenofovir or zidovudine (AZT).