Protease inhibitors are a class of antiviral drugs that block the action of proteases, enzymes that are essential for the replication of certain viruses, including the HIV virus. By inhibiting these enzymes, protease inhibitors prevent the virus from maturing and multiplying, helping to control the infection in patients. These medications are often used in combination with other antiretroviral drugs as part of a treatment regimen for HIV/AIDS. Common examples of protease inhibitors include ritonavir, lopinavir, and darunavir. Their effectiveness has significantly improved the quality of life for many individuals living with the virus.