Acquired immunodeficiency syndrome, or AIDS, is caused by the human immunodeficiency virus, HIV. HIV infects many cells of the immune system resulting in decreased immune responses to infections and cancers. The Joint United Nations Programme on HIV/AIDS estimates that more than 38 million people are infected with HIV worldwide. The U.S. Centers for Disease Control and Prevention states that every year in the U.S., 56,300 new HIV infections are reported and more than 14,000 people die from AIDS. Common therapies for HIV can help manage symptoms and could delay or prevent the onset of AIDS.
Anti-retroviral Drugs
The anti-retroviral medications to treat AIDS slow down the destruction of the immune system and some reduce the transmission of HIV. Most of the drugs inhibit the virus from replicating in cells of the immune system. Newer drugs also block the virus from entering these cells. The anti-retroviral drugs are most effective when used in combination.
MayoClinic.com cites seven classes of anti-retroviral drugs that are currently available to treat HIV infection. They are nucleoside analogue reverse transcriptase inhibitors, protease inhibitors, non-nucleoside reverse transcriptase inhibitors, nucleotide reverse transcriptase inhibitors, fusion inhibitors, integrase inhibitors, and chemokine co-receptor inhibitors. Although many of the medications available to treat AIDS have improved and extended the lives of millions of people none of them cure AIDS and many cause severe side effects. Also, people who have been on anti-retroviral drugs for many years develop resistance to the drugs and no longer respond to treatment.
Reverse Transcriptase Inhibitor Regimens
The U.S. Food and Drug Administration has approved the four nucleotide reverse transcriptase inhibitors, delavirdine, efavirenz, etravirine, and nevirapine for the treatment of HIV infection. The U.S. Department of Health and Human Services, or DHHS, has recommended three regimens for the treatment of adults and adolescents infected with HIV. The first regimen recommended by the DHHS panel is anti-retroviral therapy with the combination of the non-nucleoside reverse transcriptase inhibitor, efavirenz and the nucleotide/nucleoside reverse transcriptase inhibitors, tenofovir and emtricitabine. The DHHS reports clinical trials have found that regimens based on non-nucleoside reverse transcriptase inhibitors are effective in substantially reducing the viral load of HIV-infected patients. The DHHS reports that the disadvantage of this regimen is that nearly 7 percent of HIV-infected patients are infected with non-nucleoside reverse transcriptase inhibitor-resistant viruses.
Protease Inhibitor Regimens
The DHHS reports that protease inhibitor based regimens are also effective in reducing viral load and drug resistance to protease inhibitors is much less common. The protease inhibitors, however, cause gastrointestinal problems and metabolic abnormalities, including high triglycerides and insulin resistance. The DHHS preferred protease inhibitor based regimen is the protease inhibitor ritonavir-boosted with either atazanavir or darunavir in combination with tenofovir and emtricitabine.
Integrase Inhibitor Regimens
The last DHHS recommended regimen is based on the integrase inhibitor, raltegravir. The DHHS reported that raltegravir in combination with tenofovir and emtricitabine was as effective as efavirenz in combination with tenofovir and emtricitabine in reducing viral load and was generally well tolerated. The disadvantage of this treatment regimen is that HIV also can develop resistance to raltegravir.
