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Antiretroviral Treatment of Human Immunodeficiency Virus (HIV) Infection


Edward R. Cachay

, MD, MAS, University of California, San Diego School of Medicine

Reviewed/Revised Feb 2023 | Modified Sep 2023
Topic Resources
  • Reduce the amount of HIV RNA (viral load) in the blood to an undetectable amount

  • Restore the CD4 count to a normal level

Several classes of antiretroviral medications are used together to treat HIV infection. These medications block HIV from entering human cells or block the activity of one of the enzymes HIV needs to replicate inside human cells and/or integrate its genetic material into human DNA.

The medications are grouped into classes based on how they act against HIV:

  • Reverse transcriptase inhibitors prevent HIV reverse transcriptase from converting HIV RNA into DNA. There are three types of these medications: nucleoside, nucleotide, and non-nucleoside.

  • Protease inhibitors prevent protease from activating certain proteins inside newly produced viruses. The result is immature, defective HIV that does not infect new cells.

  • Entry (fusion) inhibitors prevent HIV from entering cells. To enter a human cell, HIV must bind to a CD4 receptor and one other receptor, such as the CCR-5 receptor. One type of entry inhibitor, CCR-5 inhibitors, blocks the CCR-5 receptor, preventing HIV from entering human cells.

  • Post-attachment inhibitors also prevent HIV from entering cells but in a different way from fusion inhibitors. These are used mainly for HIV infection that is resistant to several other medications.

  • Integrase inhibitors prevent HIV DNA from being integrated into human DNA.

  • Attachment inhibitors prevent HIV from attaching to host T cells and other immune cells; thus they are unable to enter those cells.

Sites of Medication Action on Life Cycle of HIV

Sites of Medication Action on Life Cycle of HIV

Medications used to treat HIV infection were developed based on the life cycle of HIV. These medications prevent HIV entry into its target cells or inhibit the three enzymes (reverse transcriptase, integrase, and protease) that the virus uses to replicate.

  • 1. HIV first attaches to and penetrates its target cell. The overall classes of medications that act against HIV at this stage are called entry inhibitors, and they included attachment inhibitors, post-attachment inhibitors, and fusion inhibitors.

  • 2. HIV releases RNA, the genetic code of the virus, into the cell. For the virus to replicate, its RNA must be converted to DNA. Medications called reverse transcriptase inhibitors can prevent HIV reverse transcriptase from converting HIV RNA into DNA.

  • 3. The viral DNA enters the cell’s nucleus.

  • 4. With the help of an enzyme called integrase (also produced by HIV), the viral DNA becomes integrated with the cell’s DNA. At this stage, medications called integrase inhibitors can prevent HIV DNA from being integrated into human DNA.

  • 5. The DNA of the infected cell now produces viral RNA as well as proteins that are needed to assemble a new HIV.

  • 6. A new virus is assembled from RNA and short pieces of protein.

  • 7. The virus pushes (buds) through the membrane of the cell, wrapping itself in a fragment of the cell membrane and pinching off from the infected cell.

  • 7.5 and 8. To be able to infect other cells, the budded virus must mature. Another HIV enzyme (HIV protease) is crucial to this maturation. At this stage, medications called protease inhibitors can prevent the maturation of the HIV virus.

These medications prevent HIV from replicating in cells and significantly reduce the amount of HIV in the blood over a few days to weeks. If replication is sufficiently slowed, the destruction of CD4+ lymphocytes by HIV is decreased and the CD4 count begins to increase. As a result, much of the damage to the immune system caused by HIV can be reversed. Doctors can detect this reversal by measuring the CD4 count, which begins to return toward normal levels over weeks to months. The CD4 count continues to increase for several years but at a slower rate.

Early diagnosis of HIV infection is important because it enables doctors to identify people with HIV infection before their CD4 cell count decreases too much. The sooner people start taking antiretroviral medications, the more quickly their CD4 count is likely to increase and the higher the count is likely to become.

Did You Know...

  • Medications used to treat HIV infection help only if people take the medications consistently. Missing doses enables the virus to replicate and develop resistance.

HIV invariably develops resistance to any of these medications if they are used alone. Resistance develops after a few days to several months of use, depending on the medication and the virus. HIV becomes resistant to medications because of mutations that occur when it replicates.

Treatment is most effective when two or more medications are given in combination. These combinations of medications are often referred to as combination antiretroviral therapy (cART). cART is used because

  • Combinations are more powerful than single medications in reducing the amount of HIV in the blood.

  • Combinations help prevent the development of drug resistance.

  • Some HIV medications (such as ritonavir) boost the blood levels of other HIV medications (including most protease inhibitors) by slowing their removal from the body and thus increase their effectiveness.

cART can increase the CD4 count in people with HIV infection, thus strengthening their immune system and extending their life.

Side effects of antiretroviral medications

Side effects of combinations of antiretroviral medications may be unpleasant and serious. However, doctors can prevent many serious problems (such as anemia, hepatitis, kidney problems, and pancreatitis) by regularly examining the person and doing blood tests. The blood tests can detect side effects before they become serious and enable doctors to change antiretroviral medications when needed. For most people, doctors can find a combination of medications with minimal side effects.

Metabolism of fats may be disturbed, probably primarily by protease inhibitors. The following may result:

  • Fat accumulates in the abdomen and breasts of women (called central obesity), and it is lost from the face, arms, and legs.

  • The body become less sensitive to insulin's effects (called insulin resistance)

  • Blood levels of cholesterol and triglycerides (two types of fat in the blood) are increased.

Rashes (skin reactions) are a side effect of many medications. Some skin reactions can be very dangerous, especially if the medication causing the reaction is nevirapine or abacavir.

Mitochondria (structures within cells that generate energy) can be damaged when certain nucleoside reverse transcriptase inhibitors are used. Side effects include anemia, foot pain caused by nerve damage (neuropathy), liver damage that occasionally progresses to severe liver failure, and heart damage that can result in heart failure. Individual medications differ in their tendency to cause these problems.

Bone density may decrease when cART is used, resulting in osteopenia or osteoporosis Osteoporosis Osteoporosis is a condition in which a decrease in the density of bones weakens the bones, making breaks (fractures) likely. Aging, estrogen deficiency, low vitamin D or calcium intake, and... read more Osteoporosis . Most people with these disorders do not have any symptoms, but they are at higher risk of fracturing a bone.

Immune reconstitution inflammatory syndrome

The immune reconstitution inflammatory syndrome (IRIS) sometimes occurs when cART is successful.

In IRIS, symptoms of various infections worsen or appear for the first time because immune responses improve (are reconstituted), increasing inflammation Inflammation If the body did not have defenses against infection, it would quickly be overwhelmed by microorganisms. These defenses require a living, properly functioning body. A dead body begins to decay... read more at sites of infection. Symptoms sometimes worsen because parts of dead viruses persist, triggering immune responses.

There are two forms of this syndrome:

  • Paradoxical IRIS, which refers to the worsening of symptoms of an infection that doctors have already diagnosed

  • Unmasked IRIS, which refers to the first appearance of symptoms of an infection that doctors had not previously diagnosed

Paradoxical IRIS typically occurs during the first few months of treatment and usually resolves on its own. If it does not, corticosteroids, given for a short time, are often effective. Paradoxical IRIS is more likely to be severe when cART is started soon after treatment of an opportunistic infection is started. Thus, for some (but not all) opportunistic infections, cART is delayed until treatment of the opportunistic infection has reduced or eliminated the infection.

In people with unmasked IRIS, doctors treat the newly identified opportunistic infection with antimicrobial medications. Occasionally, when the symptoms are severe, corticosteroids are also used. Usually, when unmasked IRIS occurs, cART is continued. An exception is when a cryptococcal infection Cryptococcosis Cryptococcosis is an infection caused by the fungus Cryptococcus neoformans or Cryptococcus gattii. People may have no symptoms or may have headache and confusion, a cough and... read more Cryptococcosis affects the brain. Then cART is temporarily interrupted until the infection is controlled.

Interactions with antiretroviral medications

Drug interactions Drug Interactions The effect a drug has on a person may be different than expected because that drug interacts with Another drug the person is taking (drug-drug interaction) Food, beverages, or supplements the... read more between antiretroviral medications and other medications or between two antiretroviral medications can occur. Thus, people should make sure their doctor knows all the medications they are taking.

Interactions between antiretroviral medications may increase or decrease the effectiveness of the medications.

Also, other substances affect how the body uses some HIV medications. These substances include the following:

Use of antiretroviral medications

Antiretroviral treatment is beneficial only if the medications are taken on schedule. Missing doses allows the virus to replicate and develop resistance.

Treatment cannot eliminate the virus from the body, although the HIV level often decreases so much that it cannot be detected in blood or other fluids or tissues. An undetectable level is the goal of treatment. If treatment is stopped, the HIV level increases, and the CD4 count begins to fall.

The best time to start antiretroviral treatment is as soon as possible, even if people are not sick and their CD4 count is still above 500 (normal is 500 to 1,000). Doctors used to wait until the CD4 count was below 500 to start antiretroviral treatment. However, research has shown that people who are promptly treated with antiretroviral medications are less likely to develop AIDS-related complications and to die of them.

Before starting a treatment regimen, people are taught about the necessity of the following:

  • Taking medications as directed

  • Not skipping any doses

  • Taking the medications for the rest of their life

Taking the medications as directed for a life time is demanding. Some people skip doses or stop taking the medications for a time (called a drug holiday). These practices are dangerous because they enable HIV to develop resistance to the medications.

Because taking HIV medications irregularly often leads to drug resistance, health care practitioners try to make sure that people are both willing and able to adhere to the treatment regimen. To simplify the drug schedule and to help people take the medications as directed, doctors often prescribe treatment that combines two or more medications in one tablet that can be taken only once a day.

Doctors may stop treatment temporarily if people develop another disorder that requires treatment or if side effects are severe and doctors must determine which medication is causing them. Stopping treatment is usually safe if all medications are stopped at the same time. Medications are restarted once the dose of the medication causing problems has been modified or another medication is substituted for it and doctors determine that it is safe to restart treatment. An exception is abacavir. If people have had a fever or rash when they were taking abacavir, abacavir should be permanently stopped. Such people may have a severe, potentially fatal reaction to abacavir if they take it again.

Prevention of opportunistic infections

If the CD4 count is low, medications to prevent opportunistic infections are routinely prescribed, as in the following cases:

Other medications

Other medications may help with the weakness, weight loss, and central obesity that may result from HIV infection:

  • Megestrol and dronabinol (a marijuana derivative) stimulate appetite. Many people find that natural marijuana is even more effective, and its use for this purpose has been legalized in a few states.

  • If men have low testosterone levels plus fatigue, anemia, and/or muscle loss, they may be given testosterone by injection or through patches placed on the skin. Testosterone treatments can increase testosterone levels and lessen symptoms.

  • Growth hormone and tesamorelin (an injectable medication that releases growth hormone) reduce the central obesity that may result from HIV and its treatment.

If insulin resistance develops, medications to increase sensitivity to insulin may help. If blood levels of cholesterol and triglycerides increase, lipid-lowering medications Lipid-lowering drugs Dyslipidemia is a high level of cholesterol and/or triglycerides or a low level of high-density lipoprotein (HDL) cholesterol. Lifestyle, genetics, disorders (such as low thyroid hormone levels... read more Lipid-lowering drugs (statins) can be used to lower them.

More Information

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Viramune, Viramune Suspension, Viramune XR
Ziagen, Ziagen Solution
Fortovase, Invirase
No brand name available
Primsol, Proloprim, TRIMPEX
Azasite, Zithromax, Zithromax Powder, Zithromax Single-Dose , Zithromax Tri-Pak, Zithromax Z-Pak, Zmax, Zmax Pediatric
Biaxin, Biaxin XL
Sitavig, Zovirax, Zovirax Cream, Zovirax Ointment, Zovirax Powder, Zovirax Suspension
Megace, Megace ES
Marinol, SYNDROS
Androderm, AndroGel, Andro-L.A., Aveed, AXIRON, Delatestryl, Depo-Testosterone, FORTESTA, JATENZO, KYZATREX, Natesto, STRIANT, Testim, Testoderm, Testopel, TLANDO, Virilon, Vogelxo, XYOSTED
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