Cytochrome enzyme inhibitors in HIV infection

Ritonavir and cobicistat are used solely for their enzyme inhibiting potential. Both are CYP3A4 inhibitors. 

They are used in human immunodeficiency virus infection. 

Ritonavir is a protease inhibitor and has anti HIV activity. It is used in low dose to potentiate the action of other protease inhibitors through it's cytochrome enzyme inhibition activity. 

Cobicistat doesn't have anti HIV activity and it is solely used for the purpose of cytochrome enzyme inhibition to boost the action of protease inhibitors.