Infection with the human immunodeficiency virus, or HIV, causes slowly progressive destruction of the immune system. Late-stage HIV infection, or AIDS, is characterized by vulnerability to numerous types of infections. Antiviral drugs, known as antiretrovirals, can slow the progression of HIV infection, leading to prolonged survival for people living with HIV/AIDS. Although antiretrovirals do not kill HIV, these drugs interrupt various steps in the virus replication process. Suppression of HIV replication helps preserve immune system function.
Nucleoside/Nucleotide Reverse Transcriptase Inhibitors
Nucleoside/nucleotide reverse transcriptase inhibitors, more commonly known as NRTIs or "nukes," inhibit an essential process in the HIV replication cycle. Reverse transcriptase enables the virus to copy its genes into a form that can incorporate among the genes of the immune cells. Once HIV genes incorporate among the immune cell genes, the virus remains in the cell permanently.
NRTIs disrupt the reverse transcriptase copying process, explains the patient information website HIV InSite, produced by the University of California, San Francisco Medical Center. Examples of NRTIs include zidovudine, abacavir, tenofovir, didanosine, stavudine, emtricitabine and lamivudine.
Non-nucleoside Reverse Transcriptase Inhibitors
Non-nucleoside reverse transcriptase inhibitors, commonly known as NNRTIs or "non-nukes," also inhibit the HIV reverse transcriptase enzyme, halting the gene copying process. NNRTIs, however, block the process by utilizing a different chemical mechanism than the NRTIs. NNRTIs approved by the U.S. Food and Drug Administration include etravirine, delavirdine, nevirapine and efavirenz.
Integrase Inhibitors
Integrase inhibitors block the incorporation of HIV genes into the immune cell genetic material, explains infectious disease specialist Dr. Susa Coffey on HIV InSite. As of September 2010, raltegravir remains the only integrase inhibitor to gain FDA approval for the treatment of HIV/AIDS.
Protease Inhibitors
The HIV replication process involves the production of proteins for new HIV particles. Large protein molecules are produced, which the HIV protease enzyme clips into functioning protein pieces. Protease inhibitors block the clipping process, thereby preventing the formation of functional proteins for new HIV particles. Nelfinavir, indinavir, fosamprenavir, saquinavir, atazanavir, tipranavir, ritonavir, darunavir and lopinavir/ritonavir are FDA-approved protease inhibitors, notes the pharmaceutical information website Drugs.com.
Fusion Inhibitors
Enfuvirtide belongs to the fusion inhibitor class of antiretroviral drugs. The medication binds to the outer surface of HIV particles, blocking the site where the virus normally attaches, or fuses, with the immune cell. By blocking fusion, enfuvirtide prevents HIV from infecting immune cells, reports HIV InSite. As of September 2010, enfuvirtide is the only FDA-approved fusion inhibitor for HIV/AIDS.
Entry Inhibitors
Entry inhibitors, also known as chemokine coreceptor antagonists, block a receptor on the immune cells used by HIV for entry. By blocking the receptor, the drug prevents infection of the cell by HIV. As of September 2010, maraviroc remains the lone entry inhibitor approved by the FDA.
References
- University of California, San Francisco HIV InSite: Deciding on a Treatment Plan, Nucleoside Reverse Transcriptase Inhibitors
- U.S. Food and Drug Administration: Antiretroviral Drugs Used in the Treatment of HIV Infection
- University of California, San Francisco HIV InSite: Raltegravir (Isentress)
- Drugs.com: Protease Inhibitors
- University of California, San Francisco HIV InSite: Enfuvirtide (Fuzeon)
