All of the above agents prevent the virus from reproducing and thereby slow the progression of the disease. HIV usually develops resistance to all these drugs when they are used alone after periods of a few days to a few years, depending on the drug and the person. Treatment appears to be most effective when at least two of the drugs are given in combination. Drug combinations (so-called cocktail therapy) may delay the onset of AIDS and extend life compared with the use of single drugs. Doctors aren't certain how soon after infection these drugs should be started, but people with high levels of HIV in their blood, even people with high CD4 counts and no symptoms, should be treated.

People with AIDS may also be prescribed many drugs to prevent opportunistic infections when the CD4+ lymphocyte count drops below 200 cells per microliter of blood. With the benefit of combination therapy (cocktail therapy), it is now apparent that most of the opportunistic infection prophylaxis can be withheld if the CD4 level improved beyond a safety level for the specific infection.