indinavir + ritonavir + fosamprenavir

This is a combination of three antiretroviral drugs—indinavir, ritonavir, and fosamprenavir—used in the treatment of human immunodeficiency virus (HIV) infection. All three are HIV-1 protease inhibitors that act by binding to the active site of the viral protease enzyme, thereby preventing cleavage of viral Gag and Gag-Pol polyprotein precursors into mature proteins essential for viral replication. This results in the formation of immature, non-infectious viral particles[1][2][3][4][5][10]. Ritonavir is primarily used at low doses as a pharmacokinetic booster due to its potent inhibition of cytochrome P450 3A4 (CYP3A4), which increases plasma concentrations and prolongs the half-life of other protease inhibitors such as indinavir and amprenavir (the active metabolite of fosamprenavir)[5][8]. Fosamprenavir is a prodrug rapidly converted to amprenavir after absorption[2][6]. This triple-protease inhibitor regimen has been studied for use in salvage therapy for multidrug-resistant HIV infection and may be considered when optimizing regimens with newer classes like integrase or coreceptor inhibitors[1].