abacavir + amprenavir + efavirenz

This is an oral antiretroviral combination regimen consisting of **abacavir**, **amprenavir**, and **efavirenz**. - **Abacavir** is a nucleoside reverse transcriptase inhibitor (NRTI) that inhibits HIV-1 reverse transcriptase by acting as a guanosine analog, leading to chain termination during viral DNA synthesis. - **Amprenavir** is a protease inhibitor (PI) that blocks the HIV-1 protease enzyme required for the cleavage of viral polyprotein precursors, resulting in immature, noninfectious virions. - **Efavirenz** is a non-nucleoside reverse transcriptase inhibitor (NNRTI), which acts by non-competitively inhibiting the HIV-1 reverse transcriptase enzyme. This combination targets multiple stages of the HIV-1 lifecycle for the treatment of HIV-1 infection and is typically used in salvage or later-line therapy, especially for patients with viral resistance to prior regimens. Clinical evidence suggests this regimen can be effective and generally well-tolerated in patients with prior treatment failure, but efavirenz can lower amprenavir plasma levels due to drug interaction. Main side effects: abacavir (risk of hypersensitivity reaction, GI upset, headache), amprenavir (GI symptoms, skin rash), efavirenz (CNS symptoms such as vivid dreams, dizziness), plus overlapping risk of rash and GI symptoms. It is not available as a fixed-dose combination product; pills are co-administered. This three-drug combination does not have a unique brand or code name and is not widely used as a unified regimen but has been studied in clinical trials for HIV salvage therapy[5].