Protease inhibitors prevent proteases from splitting proteins into peptides. Protease inhibitors prevent the cleavage of HIV precursor proteins into active proteins, a process that normally occurs when HIV replicates.
Protease inhibitors include saquinavir (brand name: Invirase, Fortovase) and ritonavir (brand name: Norvir) and are used primarily in HIV/AIDS treatment. They are taken as part of a two- or three-drug cocktail, accompanied by one or more nucleoside antiviral drugs.
These treatments are capable of lowering the level of HIV virus in the blood until it cannot be measured with current tools. Side effects associated with protease inhibitors include a lipodystrophy syndrome in which the face, arms and legs become thin due to loss of subcutaneous fat, the skin becomes dry, weight loss occurs, and abnormal deposits of fat occur. Some new strains of HIV are resistant to protease inhibitors.