Much progress has been made in the treatment of HIV/AIDS since AZT was first introduced in 1987; there are currently 20 approved antiviral agents.

Studies clearly show that three-drug combinations of these anti-HIV drugs are much more effective than one drug used alone or two-drug combinations in preventing disease progression and death, greatly reducing disease progression and deaths in people with AIDS. Consequently, combination anti-HIV therapy is now the standard of care for people with HIV; it is often called HAART (Highly Active Anti-Retroviral Therapy). These combinations each contain at least three drugs prescribed from the following four categories:

1. Nucleoside/tide Reverse Transcriptase Inhibitors (NRTIs), which include abacavir (Ziagen), laminvudine, 3TC (Epivir), tenofovir (Viread), abacavir/lamivudine/zidovudine (Trizivir), lamivudine/zidovudine (Combivir), stavudine, d4T (Zerit), didanosine, ddI (Videx, Videx EC), zalcitabine, ddC (HIVID), zidovudine, AZT (Retrovir), and emtricitabine FTC (Emtriva).

2. Protease Inhibitors (PIs), which include amprenavir (Agenerase), nelfinavir (Viracept), saquinavir (Fortavase), indinavir (Crixivan), ritonavir (Norvir), saquinavir (Invirase), lopinavir/ritonavir (Kaletra), atazanavir, and fosamprenavir (Lexiva).

3. Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs), which include delavirdine (Rescriptor), efavirenz (Sustiva), and nevirapine (Viramune).

4. Fusion Inhibitors (FI), enfuvirtide (Fuzeon) is the only drug in this category at this time.

To date, most clinical experience with combination therapy in treatment-naïve individuals (persons who are HIV positive with no previous history of antiviral treatment) has been based on the first three different types of combination regimens, namely: NNRTI-based (1 NNRTI + 2 NRTI), PI-based (1-2 PI + NRTI), and triple NRTI-based regimens. Recommendations are, accordingly, organized by these categories. The fourth category (FI) is currently used for individuals who have experienced prior treatment failures.

A test for measuring how well anti-HIV drugs are working is also now available. The test is called the viral load test, and measures the amount of HIV in the blood. Researchers are finding that the level of HIV in the blood is linked to a person's risk of getting sick. A study has also shown that using drug treatments to lower the level of HIV can reduce the chances that a person will get sick. Therefore, recommendations from the National Institutes for Health and the Public Health Service state that the goal of anti-HIV treatment is to keep the level of HIV (i.e., the viral load) in the body as low as possible for as long as possible.

The best combination of anti-HIV treatments to use, in order to try and achieve this goal, is not yet known for certain. Combination anti-HIV treatment should be carefully chosen based on several factors:

· Which anti-HIV treatments have I already taken?
· Which combination has the best chance of reducing the amount of HIV in my body for the longest time?
· What are my options if this combination stops working?
· How many pills will I need to take?
· What are the possible side effects of the antiviral drug combination?
· What are the possible drug interactions with any other meds I am taking?
· Am I now pregnant or likely to become pregnant?

A summary of the advantages and disadvantages antiviral drugs is provided in the table below, which is a reprint from the Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents, April 7, 2005 developed by the Panel on Clinical Practices for Treatment of HIV Infection convened by the Department of Health and Human Services (DHHS).

It is readily seen that atazanavir, fosamprenavir, and fosamprenavir/ritonavir (the newest additions to HIV antiviral drugs) allow for significantly fewer pills to be taken daily and once-daily dosing (2-4 tablets daily compared to as many as 16 tablets daily). This is a great improvement over other antivirals - especially compared to other PIs. In addition, the only disadvantage listed for fosamprenavir and fosamprenavir/ritonavir is the possibility of a skin rash.