Used as a pharmacokinetic enhancer in antiretroviral therapy for HIV. It boosts the effectiveness of certain HIV protease inhibitors by inhibiting cytochrome P450 3A (CYP3A) enzymes in the liver and intestines, which slows the breakdown of co-administered drugs. This allows lower doses of the primary antiviral agents, reduces dosing frequency, and improves overall treatment efficacy. Commonly combined with elvitegravir, darunavir, or atazanavir in fixed-dose tablet formulations. Not active against HIV itself but plays a critical supporting role in modern HIV treatment regimens.