Antiretroviral therapy (often called ARV therapy or ART) is drug therapy that has been developed to disrupt the cycle of HIV replication. ARVs come in a variety of formulations designed to act at different stages of the HIV virus life-cycle. ART usually consists of a combination of three or four different drugs, which can delay HIV replication and immune system deterioration within the body. Administering ARVs in combination is called Highly Active Antiretroviral Therapy (HAART) which is often more casually referred to as a drug cocktail.