Ritonavir (Norvir) is an anti-HIV drug that reduces the amount of virus in the body. Anti-HIV drugs such as ritonavir slow down or prevent damage to the immune system, and reduce the risk of developing AIDS-related illnesses.

Ritonavir is a protease inhibitor. Protease inhibitors act by blocking HIV’s protease, the enzyme that HIV uses to break up large viral proteins so new HIV particles can be made. For more information about how protease inhibitors work, see Protease inhibitors.

Ritonavir was approved for use in combination with nucleoside reverse transcriptase inhibitors (NRTIs) for treating adults with advanced or progressing HIV disease in Europe and the United States in late 1996.

Ritonavir is manufactured by Abbott, under the trade name Norvir. During early trials it was known as ABT-538 and A-84,538. A generic version of the drug is manufactured by Hetero / Genix under the trade name Ritovir.

Although it was originally developed for use as a protease inhibitor in its own right, today ritonavir is usually only used in low doses combined with another protease inhibitor. This boosts the levels of and increases the anti-HIV effect of the other protease inhibitor.