Human deficiency virus, or HIV, is the virus that leads to AIDS. The diseases destroy cells of the immune system, leaving patients vulnerable to infection. According to AVERT, the international AIDS charity, there were 33.4 million people worldwide living with HIV or AIDS at the end of 2008. Although it is estimated there were 2 million deaths worldwide from HIV/AIDS in 2008, it now regarded as a treatable condition and many people with HIV remain well while on medication. Four types of medicines are used to treat HIV infection.
Nucleoside Reverse Transcriptase Inhibitors
Nucleoside reverse transcriptase inhibitors, or NRTIs, are also known as "nukes" and work by stopping the HIV virus from copying its genetic code into the DNA of the infected cell. In order for the HIV virus to copy its genetic code into infected cells, it first has to convert its RNA into DNA. It does this by employing the reverse transcriptase enzyme, and it is this step that NRTIs hinder. By stopping this process, NRTIs prevent the cell from producing more of the HIV virus. An example is Epivir, also known as lamivudine, which was approved by the FDA in 1995.
Non-Nucleoside Reverse Transcriptase Inhibitors
Non-nucleoside reverse transcriptase inhibitors, or NNRTIs, work in a similar way to NRTIs in that they prevent the HIV virus for replicating by blocking its ability to deposit its DNA into the infected cell. The only difference between NRTIs and NNRTIs is the way in which they block the reverse transcriptase enzyme. An example of a NNRTI is Intelence, also known by its generic name of etravirine, which was approved by the FDA in 2008.
Protease Inhibitors
Protease inhibitors work by preventing infected CD4 cells from releasing the HIV virus into the body by blocking the action of the HIV enzyme, protease. An example of a protease inhibitor is Viracept, also known by its generic name of nelfinavir mesylate. Protease inhibitors are usually used in combination with other antiretroviral drugs. In a 2003 article published in the "Journal of Antimicrobial Chemotherapy," the lead author Paolo Monini says "...protease inhibitors (PIs), used in combination with reverse transcriptase nucleoside inhibitors (NRTIs), have turned AIDS into a chronic, manageable disease."
Fusion Inhibitors
Entry inhibitors, also known as fusion inhibitors, differ from other types of HIV drugs because they treat CD4 cells before they become infected with the HIV virus rather than afterward. They do this by attaching either to proteins on the surface of CD4 cells or proteins on the surface of HIV. In this way fusion inhibitors stop the HIV virus from binding to CD4 cells, which means the virus is unable to infect the cells. Examples of fusion inhibitors include Fuzeon, also known by its generic name of enfuvirtide, which was approved by the FDA in March 2003, and Selzentry, known by its generic name of maraviroc, which was approved in 2007.
