HIV is a type of virus called a "retrovirus." Consequently, drug treatments to fight HIV are properly called "antiretrovirals" (ARV), but people usually use the simpler word "antivirals." Antiretrovirals interfere with the life cycle of HIV by slowing down or stopping the process by which the virus makes copies of itself. When there are fewer viruses available to infect CD4 cells (these are cells that protect us against infections), the number of those cells may increase, and thus improve the immune system.
HIV can mutate (change) so that a drug no longer has an effect. This is called resistance. Taking three or more ARVs (combination therapy) together makes it harder for HIV to change in ways that allow it to resist any one drug. The most recent studies show that combination therapy has longer-lasting benefit than monotherapy (taking one drug only) or duotherapy (taking two drugs only).
The greatest benefit from combination therapy is achieved if you take the drugs as they are prescribed. This is called "adherence." Many people may have difficulty taking pills, since it may involve remembering to take many pills several times per day. Some drugs must be taken on an empty stomach, others with a meal. It is very important to think about how you will take your pills before you begin taking a particular combination of drugs.
Choosing which drugs to combine can be difficult. The "right" combination for you will depend on what drugs you have taken before, which side effects you may experience, how able you are to adhere with the dosing requirements, and other infections or health conditions you may have.
When to begin ARV therapy is somewhat debatable. Most would agree that with a CD4 count below 350 or a viral load above 30,000 copies/ml one should consider beginning drug therapy. The following are the ARV medications available at the present time:
