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

Atazanavir is one of the protease inhibitors. Protease (or proteinase) is the protein or 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.

Atazanavir was developed by Bristol-Myers Squibb, the makers of d4T (stavudine, Zerit) and ddI (didanosine, Videx / VidexEC). It is also known by the names BMS-232632 and Zrivada, and is marketed under the brand name Reyataz in Europe and the United States.

In the European Union, atazanavir was approved for use in treatment-experienced patients in March 2004, at a dose of 300mg, boosted with 100mg ritonavir (Norvir) once a day. In the United States, atazanavir was approved as an anti-HIV treatment in June 2003 without restrictions on its use. The approved dose is 400mg once daily without ritonavir boosting.

European medicines regulators want to see more follow-up information before they give approval for atazanavir to be dosed without ritonavir.