At what stage of HIV is Ritanovir used?

Ritonavir is an antiretroviral drug used in combination with other medications to treat HIV infection. It is typically used in the later stages of HIV, when the virus has become resistant to other drugs. Ritonavir is used to boost the levels of other antiretroviral drugs in the blood, making them more effective at fighting the virus. It is also sometimes used to prevent HIV infection in people who are at high risk of exposure to the virus.