Ritonavir at full dose was originally used as a protease inhibitor in HIV treatment. In modern ART, subtherapeutic doses of ritonavir are combined with other protease inhibitors. The primary purpose of this combination is:

• A Direct inhibition of HIV reverse transcriptase
• B Inhibition of HIV integrase enzyme
• C Blocking CCR5 coreceptor on host cell surface
• D Inhibition of CYP3A4 to boost levels of coadministered protease inhibitor ✓

Explanation

Ritonavir is a potent CYP3A4 inhibitor. At low doses, it is used as a pharmacokinetic booster to inhibit metabolism of coadministered protease inhibitors such as darunavir or atazanavir, thereby increasing their plasma concentrations and half-life. This boosting strategy allows less frequent dosing and improved efficacy. Cobicistat serves a similar boosting purpose without antiviral activity.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

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Written and medically reviewed by the StethoPrep medical team.