zidovudine + abacavir + lamivudine + NNRTI

This refers to a combination antiretroviral therapy regimen for HIV infection that includes three nucleoside reverse transcriptase inhibitors (NRTIs)—zidovudine, abacavir, and lamivudine—plus a non-nucleoside reverse transcriptase inhibitor (NNRTI). The fixed-dose combination of zidovudine, abacavir, and lamivudine is available as Trizivir. These agents work by inhibiting the action of HIV reverse transcriptase through different mechanisms. NRTIs act as chain terminators during viral DNA synthesis, while NNRTIs bind directly to reverse transcriptase at a site distinct from NRTIs and cause conformational changes that inhibit enzyme activity. This regimen is used in the treatment of human immunodeficiency virus type 1 (HIV-1) infection[2][3][4][5]. Developers and manufacturers for individual components include ViiV Healthcare for Trizivir[1]. The addition of an NNRTI such as efavirenz or nevirapine is common in clinical practice but not part of any single co-formulated product.