Description: Raltegravir, also known as MK-0518, is an antiretroviral drug used to treat HIV infection. Raltegravir is a human immunodeficiency virus (HIV) integrase strand transfer inhibitor (HIV-1 INSTI) with HIV-1 antiviral activity. Raltegravir binds to and inhibits integrase, an HIV enzyme that inserts viral genetic material into the genetic material of the infected human cell. Inhibition of integrase prevents insertion of HIV DNA into the human DNA genome, thus blocking HIV replication. It received approval by the U.S. Food and Drug Administration (FDA) in October 2007, the first of a new class of HIV drugs, the integrase inhibitors, to receive such approval.