Cidofovir is an antiviral medication that prevents certain viral cells from multiplying in your body. Cidofovir is used to treat an eye infection called cytomegalovirus retinitis (CMV) in people who have AIDS (acquired immunodeficiency syndrome). Cidofovir is not a cure for CMV or AIDS. Cidofovir is for treating CMV only in people who have AIDS. Cidofovir may also be used for purposes not listed in this medication guide.