Ritonavir boosting: In a fixed-dose combination approved in 2000, ritonavir is used to boost the bioavailability of which protease inhibitor?

Ritonavir boosting: In a fixed-dose combination approved in 2000, ritonavir is used to boost the bioavailability of which protease inhibitor?

• A. Saquinavir
• B. Indinavir
• C. Nelfinavir
• D. Lopinavir

Answer: (D)

Ritonavir boosting relies on inhibiting the enzymes that normally break down other protease inhibitors, thereby increasing their blood levels. In the fixed-dose combination approved in 2000, ritonavir is paired with lopinavir to raise lopinavir exposure. Lopinavir has limited bioavailability because CYP3A4 rapidly metabolizes it; when ritonavir inhibits this enzyme, lopinavir stays in the system longer and at higher concentrations, enhancing its antiviral effect with convenient dosing. Ritonavir is used at a low boosting dose to boost the coadministered protease inhibitor rather than for its own antiviral activity.

Ritonavir boosting relies on inhibiting the enzymes that normally break down other protease inhibitors, thereby increasing their blood levels. In the fixed-dose combination approved in 2000, ritonavir is paired with lopinavir to raise lopinavir exposure. Lopinavir has limited bioavailability because CYP3A4 rapidly metabolizes it; when ritonavir inhibits this enzyme, lopinavir stays in the system longer and at higher concentrations, enhancing its antiviral effect with convenient dosing. Ritonavir is used at a low boosting dose to boost the coadministered protease inhibitor rather than for its own antiviral activity.