Ritonavir is an antiviral medication primarily used to treat HIV infection. It works by inhibiting a specific enzyme called protease, which is essential for the virus to replicate. By blocking this enzyme, Ritonavir helps reduce the amount of virus in the body, allowing the immune system to function more effectively. Originally developed as a standalone treatment, Ritonavir is now often used in combination with other antiretroviral drugs to enhance their effectiveness. It is also used in lower doses to boost the effects of other medications, making it a valuable component in HIV therapy regimens.