Note: this site last updated in 2006
An article from "The Molecules of HIV" (c) Dan Stowell
Highly Active Anti-Retroviral Therapy (HAART) consists of 3 or more highly potent anti-HIV drugs, commonly reverse%20transcriptase%20inhibitors">reverse%20transcriptase">reverse transcriptase inhibitors and protease inhibitors.
The principle that lies behind HAART is that a single drug therapy may be successful for a while, but because HIV changes to avoid detection, drug-resistant strains will often arise in the patient. (This happens through a kind of evolution by natural selection - any new viruses which happen to be resistant to the drug will go on to multiply, while the others are stopped.) The chances of a HIV genome mutating such that it can resist three separate drug treatments at once, however, is so small that the pressure of this therapy prevents the emergence of resistant strains.