abacavir + lamivudine + zidovudine + efavirenz

**Abacavir + lamivudine + zidovudine + efavirenz** is a combination of four antiretroviral drugs, used in the management of Human Immunodeficiency Virus (HIV) infection. This regimen combines three nucleoside reverse transcriptase inhibitors (NRTIs)—abacavir, lamivudine, and zidovudine—and one non-nucleoside reverse transcriptase inhibitor (NNRTI)—efavirenz. The NRTIs act by inhibiting HIV reverse transcriptase via incorporation into viral DNA, resulting in chain termination during DNA synthesis. Efavirenz directly inhibits HIV-1 reverse transcriptase by binding to an allosteric site, preventing the enzyme from functioning effectively. This multi-drug regimen disrupts HIV replication at several points, reduces viral load, and delays progression of disease. It may be used in certain resource-limited settings or tailored treatment strategies but is less common as there is no fixed-dose combination tablet containing all four ingredients.