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Date Posted: 13:12:51 01/26/02 Sat
Author: No name
Subject: DRUGS;ETC.

WHAT IS ANTIVIRAL THERAPY?

Antiviral therapy means treating viral infections like HIV with drugs. The drugs slow down the growth of the virus. When the virus is slowed down, so is HIV disease. Because HIV is a retrovirus, these drugs are sometimes called antiretroviral therapy.



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WHAT IS THE HIV LIFE CYCLE?

There are several steps in the HIV life cycle. See Fact Sheet 415 for a diagram.

1. Free virus circulates in the bloodstream.
2. HIV attaches to a cell.
3. HIV empties its contents into the cell (infects the cell).
4. The HIV genetic code (RNA) is changed into DNA by the reverse transcriptase enzyme.
5. The HIV DNA is built into the infected cell's DNA by the integrase enzyme.
6. When the infected cell reproduces, it activates the HIV DNA, which makes the raw material for new HIV viruses.
7. Packets of material for a new virus come together.
8. The immature virus pushes out of the infected cell in a process called "budding."
9. The immature virus breaks free of the infected cell.
10. The new virus matures: raw materials are cut by the protease enzyme and assembled into a functioning virus.



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WHAT ARE THE ANTIVIRAL DRUGS?

Each type, or "class", of antiviral drugs attacks HIV in a different way. The first class of anti-HIV drugs was the nucleoside reverse transcriptase inhibitors, also called "nukes". These drugs work by blocking Step 4, where the HIV genetic material is converted from RNA into DNA. Approved drugs in this class include:

AZT (ZDV, zidovudine, Retrovir®)
ddI (didanosine, Videx®)
ddC (zalcitabine, Hivid®)
d4T (stavudine, Zerit®)
3TC (lamivudine, Epivir®)
Abacavir (Ziagen®)
Tenofovir (Viread®)
Combivir® (AZT/3TC combination)
Trizivir® (AZT/3TC/Abacavir combination)
Another class of drugs blocks the same step of the life cycle, but in a different way. This class is the non-nucleoside reverse transcriptase inhibitors, or NNRTIs. Three NNRTIs have been approved:

Nevirapine (NVP, Viramune®)
Delavirdine (DLV, Rescriptor®)
Efavirenz (EFV, Sustiva®)
There has been a lot of excitement about the third class of antiviral drugs, the protease inhibitors. These drugs block Step 7, where the raw material for new HIV virus is cut into specific pieces. Five protease inhibitors have been approved:

Saquinavir (SQV, Invirase® and Fortovase®)
Indinavir (IDV, Crixivan®)
Ritonavir (RTV, Norvir®)
Nelfinavir (NFV, Viracept®)
Amprenavir (APV, Agenerase®)
Lopinavir (LPV, Kaletra®)


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HOW ARE THE DRUGS USED?

When HIV multiplies, most of the new copies are mutations: they are slightly different from the original virus. Some mutations keep multiplying even when you are taking an antiviral drug. When this happens, the drug will stop working. This is called "developing resistance" to the drug.

If only one antiviral drug is used, it is easy for the virus to develop resistance. But if two drugs are used, a successful mutant would have to "get around" both drugs at the same time. And if three drugs are used, especially if they attack HIV at different points in its life cycle, it's very hard for a mutation to show up that can resist all three drugs at the same time.

Using a triple-drug combination means that it takes much longer for resistance to develop. For this reason, using just one antiviral drug (monotherapy) is not recommended.



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CAN THESE DRUGS CURE AIDS?

A blood test called the "viral load" measures the amount of HIV virus in your bloodstream. People with lower viral loads stay healthier longer. See Fact Sheet 413 for more information on the viral load test.

Some people's viral load is so low that it is "undetectable" by the viral load test. This does not mean that all the virus is gone. Researchers used to believe that antiviral therapy could eventually kill off all of the HIV virus in the body. Now this seems unlikely.



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WHEN DO I START?

There is not a clear answer to this question. Most doctors will consider three things: 1) your viral load; 2) your T-cell count; and 3) any symptoms you've had. Antiviral therapy is usually started if your viral load is over 30,000, if your T-cell count is below 350, or if you've had any symptoms of HIV disease. This is an important decision you should discuss with your doctor.



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WHICH DRUGS DO I USE?

Each antiviral drug has side effects. Some are serious. Refer to the fact sheet for each individual drug. Some combinations of drugs are easier to tolerate than others, and some seem to work better than others. Each person is different, and you and your doctor will have to decide which drugs to use.

The viral load test is now being used to see if antiviral drugs are working. If the viral load does not go down, or if it goes down but comes back up, it might be time to change antiviral drugs.



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WHAT'S NEXT?

New drugs are being developed in all three of the existing classes. Researchers are also trying to develop new types of drugs, such as drugs that will block HIV from attaching to cells (Step 2), and drugs that will strengthen the body's immune defenses.



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Revised January 9, 2002

WHY DO THE GUIDELINES KEEP CHANGING?

The best way to fight HIV changes as we learn more about how to use new drugs. In 1998, the US Department of Health and Human Services created a panel of physicians, researchers, and consumers to develop and revise treatment guidelines. The panel released the latest version of these guidelines in February 2001.

NOTE: These are guidelines, not rules. Patients should receive individualized care from a doctor with experience treating HIV infection. The full text of these guidelines is available on the Internet at http://www.hivatis.org/trtgdlns.html



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VIRAL LOAD TESTING

Viral load testing provides critical information for decisions on antiviral therapy. Viral load should be tested:

Before starting or changing medications, to get a reference value;
About 2 to 8 weeks after starting or changing medications, to see if the new drugs are working;
Every 3 or 4 months to make sure the medications are still working; or, for patients not yet taking medications, to help decide when to start.


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RESISTANCE TESTING

Viral resistance testing helps doctors choose the most effective drugs. It is recommended when viral load is not controlled by new medications, or when it "breaks through" a regimen that used to work. The tests also indicate if someone got infected with drug-resistant virus.


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WHEN TO START TREATMENT

Patients with symptoms of HIV disease should all be treated.
Patients with no symptoms who have less than 350 T-cells OR viral load over 30,000* should be offered treatment. Consider the risk of disease progression and the patient's willingness to start therapy. Some experts would delay treatment for patients with 200 to 350 T-cells and viral loads under 30,000.
Patients with no symptoms who have more than 350 T-cells AND viral load below 30,000* do not need to start treatment. They should get regular blood tests. However, some experts would begin treatment for these patients.


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GOALS OF THERAPY

The guidelines list the following goals for HIV therapy:

Reduce viral load as much as possible for as long as possible
Restore or preserve the immune system
Improve the patient's quality of life
Reduce sickness and death due to HIV
The following tools are suggested to help achieve these goals:

Maximize adherence. Help the patient take medications correctly.
Think about future regimens when choosing drugs. Keep future options open
Use resistance testing when it will help.


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WHAT DRUGS SHOULD BE USED AT FIRST?


The guidelines recommend using 2 nucleoside analogs (nukes) plus one of the following:

the protease inhibitors indinavir or nelfinavir;
double-protease combinations of ritonavir plus saquinavir, indinavir or lopinavir; or
the NNRTI efavirenz.
Other drugs and combinations are recommended as alternatives. The guidelines do not comment on the use of hydroxyurea. They discourage the use of a single drug (monotherapy), or of two nukes.




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INTERRUPTING TREATMENT

A patient may need to interrupt treatment if they can't tolerate the side effects, if there's a drug interaction, if they run out of any of the drugs, or for women who choose to stop treatment during the first 3 months of pregnancy.

If antiviral therapy is stopped, all drugs should be stopped at the same time, and re-started together. This will reduce the risk of the virus developing resistance to the medications.



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WHEN TO CHANGE


Treatment should be changed due to treatment failure, or intolerance of current drugs.

Treatment failure: Treatment failure: Compare the viral load to the reference level (before the current medications). Within 8 weeks, there should be about a 90% drop in viral load. Within 6 months, the viral load should be less than 50 copies. If the viral load does not drop this much, change the treatment.

Other signs of treatment failure include:


An increase in viral load from undetectable to detectable levels, or to more than 3 times its lowest level on the current drugs;
A continuing drop in T-cells; or
A new AIDS-related illness.
Intolerance: If a patient cannot take the prescribed drugs because of their side effects or interactions with other needed medications, the drugs should be changed.



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WHAT TO CHANGE TO?

Decisions to change antiviral therapy should be based on the reason for changing, how sick the patient is, medications previously used, other drugs currently available, the side effects the patient has had, and what other medications are being used.

Changes due to drug intolerance: Reduce the dose of the drug causing the problems, or replace it with one or more drugs from the same class and of the same strength.

Changes due to treatment failure:

Use at least two new drugs, and preferably an entirely new combination.
If possible, it is best to avoid using any drug a patient has used before.
Do not switch to any drug that has shown cross-resistance with a drug now being used: don't switch between ritonavir and indinavir, or between nevirapine and delavirdine.
If there are few options to change to, and viral load was reduced, it may make sense not to change medications. Another choice may be to combine two protease inhibitors, or a protease inhibitor and an NNRTI.
Doctors who are less experienced in treating people with HIV should consult with a more experienced physician on decisions about changing antiviral therapies.


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*NOTE: These viral load levels are for tests done using the branched DNA (bDNA) technique. Tests using the polymerase chain reaction (PCR) give higher results. A 30,000 result by bDNA is equivalent to a 55,000 result by PCR. See Fact Sheet 413 for more information on viral load testing.



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WHAT ARE T-CELLS?

T-cells are a type of lymphocyte (white blood cell). They are an important part of the immune system. There are two main types of T-cells. T-4 cells, also called CD4+, are "helper" cells. They lead the attack against infections. T-8 cells, (CD8+), are "suppressor" cells that end the immune response. CD8+ cells can also be "killer" cells that kill cancer cells and cells infected with a virus.

Researchers can tell the T-cells apart by specific proteins on the cell surface. These proteins are also called "receptor sites" because they can lock onto certain molecules. So a T-4 cell is a T-cell with a CD4 receptor on its surface. This type of T-cell is also called "CD4 positive", or CD4+.



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WHY ARE T-CELLS IMPORTANT IN HIV?

When HIV infects humans, the cells it infects most often are CD4+ cells. The virus becomes part of the cells, and when they multiply to fight an infection, they also make more copies of HIV.

When someone is infected with HIV for a long time, the number of CD4+ cells they have (their T-cell count) goes down. This is a sign that the immune system is being weakened. The lower the T-cell count, the more likely the person will get sick.

There are millions of different families of T-cells. Each family is designed to fight a specific type of germ. When HIV reduces the number of T-cells, some of these families can be totally wiped out. You can lose the ability to fight off the particular germs those families were designed for. If this happens, you might develop opportunistic infections.



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HOW ARE THE TEST RESULTS REPORTED?

T-cell tests are normally reported as the number of cells in a milliliter of blood. There is some disagreement about the normal range for T-cell counts, but CD4+ counts are between 500 and 1600, and CD8+ counts are between 375 and 1100. CD4+ counts drop dramatically in people with HIV, in some cases down to zero.

The ratio of CD4+ cells to CD8+ cells is often reported. This is calculated by dividing the CD4+ value by the CD8+ value. In healthy people, this ratio is between 0.9 and 1.9, meaning that there are about 1 to 2 CD4+ cells for every CD8+ cell. In people with HIV infection, this ratio drops dramatically, meaning that there are many times more CD8+ cells than CD4+ cells.

The T-cell value bounces around a lot. Time of day, fatigue, and stress can affect the test results. It's best to have blood drawn at the same time of day for each T-cell test, and to use the same laboratory.

Infections can have a large impact on T-cell counts. When your body fights an infection, the number of white blood cells (lymphocytes) goes up. CD4+ and CD8+ counts go up, too. Vaccinations can cause the same effects. Don't check your T-cells until a couple of weeks after you recover from an infection, or after you get a vaccination.

Because the T-cell counts are so variable, some doctors prefer to look at the T-cell percentages. These percentages refer to total lymphocytes. If your test reports CD4+% = 34%, that means that 34% of your lymphocytes were CD4+ cells. This percentage is more stable than the number of T cells. The normal range is between 20% and 40%.



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WHAT DO THE NUMBERS MEAN?

The meaning of CD8+ cell counts is not clear, but it is being studied.

Most researchers believe that the CD4+ cell count is a good measure of the health of the immune system. The lower the count, the greater damage HIV has done. But some people with almost no CD4+ cells have stayed healthy for a long time.

CD4+ counts are used together with the viral load to estimate how long someone will stay healthy. See Fact Sheet 413 for more information on the viral load test.

CD4+ counts are now used to indicate when to start certain types of drug therapy:

When to start antiviral therapy:
When the CD4+ count goes below 350, most doctors begin antiviral drugs such as AZT, ddI, or 3TC. Also, some doctors use the CD4+% going below 15% as a sign to start aggressive antiviral therapy, even if the CD4+ count is high.

However, the viral load test has become at least as important as the CD4+ count in deciding when to start antiviral drugs.

When to start drugs to prevent opportunistic infections:
Most doctors prescribe drugs to prevent opportunistic infections at the following CD4+ levels:

Less than 200: pneumocystis carinii pneumonia (PCP)
Less than 100: toxoplasmosis and cryptococcosis
Less than 75: mycobacterium avium complex (MAC).


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WHAT IS VIRAL LOAD?

The viral load test measures the amount of HIV virus in your blood. There are different techniques for doing this:

The PCR (polymerase chain reaction) test uses an enzyme to multiply the HIV in the blood sample. Then a chemical reaction marks the virus. The markers are measured and used to calculate the amount of virus. Roche produces this test.
The bDNA (branched DNA) test combines a material that gives off light with the sample. This material connects with the HIV particles. The amount of light is measured and converted to a viral count. Chiron produces this test.
The PCR test results are usually about double the bDNA results for the same sample. Because the tests are different, you should stick with the same kind of test (PCR or bDNA) to measure your viral load over time.

Viral loads are usually reported as copies of HIV in one milliliter of blood. The tests count up to about 1.5 million copies, and are always being improved to be more sensitive. The first bDNA test measured down to 10,000 copies. The second generation could detect as few as 500 copies. Now there are ultra sensitive tests that can detect less than 5 copies.

The best viral load test result is "undetectable". This does not mean that there is no virus in your blood; it just means that there is not enough for the test to find and count. With the first generation test, "undetectable" could mean 9,999 copies. "Undetectable" depends on the sensitivity of the test used on your blood sample.



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HOW IS THE TEST USED?

The viral load test is helpful in several areas:

In basic science, the test has been used to prove that HIV is never "latent" but is always multiplying. Many people with no symptoms of AIDS and high T-cell counts also had high viral loads. If the virus was latent, the test wouldn't have found any HIV in the blood.
The test can be used for diagnosis, because it can detect a viral load at any time after HIV infection. This is better than the standard HIV (antibody) test, which can be "negative" after HIV infection and before the development of antibodies (See Fact Sheet 102 for more information on HIV antibody testing).
For prognosis, viral load can help predict how long someone will stay healthy. The higher the viral load, the faster HIV disease progresses.
Finally, the viral load test is valuable for managing therapy, to see if antiviral drugs are controlling the virus. Current guidelines suggest measuring baseline (pre-treatment) viral load. A drug is "working" if it lowers viral load by at least 90% within 8 weeks. With good antiviral therapy, the viral load should continue to drop to less than 50 copies within 6 months.


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HOW ARE CHANGES IN VIRAL LOAD MEASURED?

Repeat tests of a blood sample can give results that vary by a factor of 3. This means that a meaningful change would be a drop to less than 1/3 or an increase to more than 3 times the previous test result. For example, a change from 200,000 to 600,000 is within the normal variability of the test. A drop from 50,000 to 10,000 would be significant. The most important change is to reach an undetectable viral load.

Viral load changes are often described as "log" changes. This refers to scientific notation, which uses powers of 10. For example, a 2-log drop is a drop of 102 or 100 times. A drop from 60,000 to 600 would be a 2-log drop.



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WHAT DO THE NUMBERS MEAN?

There are no "magic" numbers for viral loads. We don't know how long you'll stay healthy with any particular viral load. We don't know if 150,000 is twice as bad as 75,000. All we know so far is that lower is better and seems to mean a longer, healthier life.

US treatment guidelines (See Fact Sheet 411) suggest that anyone with a viral load over 30,000 by bDNA should be treated with antiviral drugs.

Some people may think that if their viral load is undetectable, they can't pass the HIV virus to another person. THIS IS NOT TRUE. There is no "safe" level of viral load. Even if your viral load is undetectable, you can pass HIV to another person.



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ARE THERE PROBLEMS WITH THE VIRAL LOAD TEST?

There are some concerns with the viral load test:

Some scientists think that only 2% of the HIV in your body is in the blood. The viral load test does not measure how much HIV is in body tissues like the lymph nodes, spleen, or brain. HIV levels in lymph tissue go down when blood levels go down, but not at the same time or the same rate. Viral levels in semen seem to be unrelated to blood levels.
The viral load test results can be thrown off if your body is fighting an infection, or if you have just received an immunization (like a flu shot). You should not have blood taken for a viral load test within four weeks of any infection or immunization.


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WHAT IS RESISTANCE?

HIV is "resistant" to a drug if it keeps multiplying rapidly while you are taking the drug. Changes (mutations) in the virus cause resistance. HIV mutates almost every time a new copy is made. Not every mutation causes resistance. The "wild type" virus is the most common form of HIV. Anything different from the wild type is considered a mutation.

Antiviral drugs control most types of the virus. However, they won't control resistant virus. It can "escape" from the drug. As long as you take the drug, the resistant virus will multiply the fastest. This is called "selective pressure."

If you stop taking medications, there is no selective pressure. The wild type virus will multiply the fastest. We don't know if drug resistance goes away, or if it comes back when you re-start the same drugs.

Resistance testing helps doctors make better treatment decisions for their patients.



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HOW DOES RESISTANCE DEVELOP?
HIV usually becomes resistant when someone is taking drugs that don't totally control it. However, more people are getting infected with HIV that is already resistant to one or more anti-HIV drugs.

The more that HIV multiplies, the more mutations show up. These mutations happen by accident. The virus doesn't "figure out" which mutations will resist medications.

Just one mutation can make HIV resistant to some drugs. This is true for 3TC (Epivir) and the non-nucleoside reverse transcriptase inhibitors (NNRTIs). However, HIV has to go through a series of mutations to develop resistance to other drugs, including most protease inhibitors.

The best way to prevent resistance is to control HIV by taking strong antiviral medications. If you miss doses of your medications, HIV will multiply more easily. More mutations will occur. Some of them could cause resistance.

If you have to stop taking any antiviral medication, talk to your doctor. You may have to stop some drugs sooner than others. If you stop taking drugs while the virus us under control, you should be able to use them again.



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TYPES OF RESISTANCE
There are three types of resistance:


Clinical resistance: HIV multiplies rapidly in your body even though you're taking antiviral drugs.
Phenotypic resistance: HIV multiplies in a test tube when antiviral drugs are added.
Genotypic resistance: The genetic code of HIV has mutations that are linked to drug resistance.
Laboratory tests can measure phenotypic and genotypic resistance.


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PHENOTYPIC TESTING
A sample of HIV is grown in the laboratory. A dose of one antiviral drug is added. The growth rate of the HIV is compared to the rate of wild type virus. If the sample grows more than normal, it is resistant to the medication.

Phenotypic resistance is reported as "fold" resistance. If the test sample grows twenty times as much as normal, it has "20-fold resistance".

Phenotypic tests cost about $800. It used to take over a month to get the results. New phenotypic tests are quicker.



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GENOTYPIC TESTING
The genetic code of the sample virus is compared to the wild type. The code is a long chain of molecules called nucleotides. Each group of three nucleotides, called a "codon", defines a particular amino acid used to build a new virus.

Mutations are described by a combination of letters and numbers, for example K103N. The first letter (K) is the code for the amino acid in the wild type virus. The number (103) identifies the mutant codon. The second letter (N) is the code for the "changed" amino acid in the mutant sample.

Genotypic testing costs about $250. Results come back in about two weeks.



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VIRTUAL PHENOTYPE

This test combines some elements of genotypic and phenotypic testing. First, genotypic testing is done on the sample. Phenotypic test results for other virus samples with a similar genotypic pattern are taken from a database. These matched samples tell you how the virus is likely to behave. The virtual phenotype is faster and less expensive than a phenotypic test.


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CROSS-RESISTANCE
Sometimes a mutant version of HIV is resistant to more than one drug. When this happens, the drugs are called "cross-resistant". For example, most HIV that is resistant to indinavir (Crixivan) is also resistant to ritonavir (Norvir). This means that indinavir and ritonavir are cross-resistant.

Cross-resistance is important when you change medications. You need to choose new drugs that are not cross-resistant to drugs you've already taken.

We do not totally understand cross-resistance. However, many drugs are at least partly cross-resistant. As HIV develops more mutations, it gets harder to control. Take every dose of your antiviral medications according to instructions. This reduces the risk of resistance and cross-resistance. It saves the most options for changing medications in the future.



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PROBLEMS WITH RESISTANCE TESTING
Resistance tests are not available everywhere. They are expensive. However, they are becoming more common, faster and cheaper.

The tests aren't good at detecting "minority" mutations (less than 20% of the virus population.) Also, they work better when the viral load is higher. If your viral load is very low, the tests might not work.

Test results can be difficult to understand. Sometimes they don't explain what actually happens with a patient. Drugs that should work according to the tests sometimes don't work, and vice versa.

Despite these problems, many researchers believe that resistance testing will become a normal part of HIV treatment in the next several years. More physicians will probably use resistance testing before choosing someone's first antiviral medications to see if they were infected by drug-resistant virus.



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Revised December 2, 2001

HOW DO AIDS DRUGS WORK?
The HIV virus can make millions of copies of itself every day. Antiviral drugs can't kill the virus, but they can almost stop it from multiplying.

A "viral load" test measures the amount of virus in your blood. If you take anti-HIV drugs, the amount of virus in your blood should go down. If your viral load is very low, you probably won't develop any AIDS-related illnesses. See Fact Sheet 413 for more information on viral load.



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WHAT IS RESISTANCE?
The HIV virus is sloppy when it makes copies of itself. Many new copies of HIV are slightly different from the original (mutations). Some mutations can multiply easily even though you are taking drugs that stop "normal" HIV. This is called "developing resistance" to the drugs. If your virus develops resistance, it will multiply faster and your HIV disease will probably get worse.

Resistance develops quickly if you take just one drug. If you take three drugs, HIV multiplies much more slowly and it is much harder for resistance to develop.

Sometimes, when HIV becomes resistant to a drug you are taking, it will also be resistant to other antiviral drugs - even if you haven't used them yet. This is called "cross-resistance". Many HIV drugs are at least partly cross-resistant. If your virus develops resistance to an HIV drug, you might not be able to use any other drugs of the same type. To avoid using up your treatment options, take all of your medications according to instructions.



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KEEPING PRESSURE ON THE VIRUS
When you take medications, they get into your blood and are carried around your body. Then your liver and kidneys start to clean the drug out of your system, and the amount of medication in your blood goes down.

Some drugs get into your bloodstream better if there is no food in your stomach. You take these medications on an empty stomach. Other drugs get into your bloodstream better if your stomach is full. You should take these drugs with food. With some drugs, food doesn't matter.

The instructions for taking each drug tell you how many pills to take, when to take them, and how to take them, in order to keep enough medicine in your blood. If you skip a dose, don't take a full dose, or don't follow the eating instructions, the drug levels in your blood will drop.

If there is not enough medicine in your blood, HIV can continue to multiply. The more HIV multiplies, the greater the chance that resistance will develop.

The best way to keep pressure on HIV is to take all the pills you're supposed to, every time you're supposed to, and follow the directions about food.



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HOW MUCH ADHERENCE IS ENOUGH?
Adherence means taking your medications correctly. If you don't, HIV might multiply out of control. Several research studies have measured how much adherence is "enough." They found that, for the best viral load results, people had to take 90% to 95% of their pills correctly. If you take pills three times a day, this means that you don't miss more than one dose a week.



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MAKE IT EASY ON YOURSELF
It can be difficult to take your medications the way you're supposed to. Make it as easy as you can!

Tell your doctor about your daily schedule so that you can choose the medications that will be easiest for you to take.
Make sure you understand your medications:
Which medications to take
How many pills to take, and how many times a day
Whether to take your pills with food, or on an empty stomach
How to store your pills
Side effects you might have, and what to do about them
Plan ahead so you don't run out of any of your medications.
Use a pillbox and count your pills out ahead of time. Some boxes hold enough for a whole week.
Set a timer or alarm to go off when you have to take pills.
Choose a regular daily activity to help you remember to take pills:
Making your morning coffee
Getting out of bed
A favorite TV show
Coming home from work
Make sure your family members know how important it is for you to take your pills. Ask them to help you remember.
You might have problems with side effects, or it might be difficult to take your pills as prescribed. Don't cut back or stop taking your medications until you have talked to your doctor. You might be able to change your medications and get some that are easier for you to take.


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THE BOTTOM LINE
In order for your medications to work, you need to take them according to the instructions. If you don't, your virus might develop resistance to drugs you are taking. If your virus becomes resistant to one drug, it might also be resistant to other HIV drugs. For the best results you have to take over 90% of your pills correctly.

Be sure that you understand which medications your doctor has prescribed. Make sure you know how many to take, when to take them, and whether you need to take them with food or when your stomach is empty.

Work with your health care provider to make it as easy as possible to take your medications. Use whatever you need to keep on your medication program: pillboxes, timers, friends, or support groups. Be sure to talk with your doctor before you make any changes in your medications or how you take them.



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Revised August 23, 2001

WHAT ARE TREATMENT INTERRUPTIONS?
Many people with HIV infection stop taking antiviral medications for various reasons. Their viral load climbs very quickly and their T-cell count drops. In late 1997, however, an HIV patient in Berlin stopped taking medications. His viral load climbed briefly, then dropped and stayed undetectable.

This patient started medications soon after he was infected. Maybe HIV didn't have a chance to damage his immune system. Maybe his viral load increase was like a vaccination that stimulated his immune system to control the virus.

Researchers immediately tried to copy the Berlin patient's success in other patients. They stopped treatment for a certain period of time, or until the viral load climbed to a certain point. This kind of treatment interruption is called "STI" which means either "structured" or "strategic" treatment interruption.


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WHICH PATIENTS ARE BEING STUDIED, AND WHY?
STI studies are divided according to three groups of HIV patients:

HIV is under control; antiviral treatment started within six months of infection. These "primary infection" patients, like the Berlin patient, may have the best chance to control HIV without medications.
HIV is under control; treatment started more than six months after infection. These "chronic infection" patients may just want a break from taking medications, or may want to reduce side effects.
HIV is not controlled by antiviral medications. These "drug-resistant" patients may want a break from side effects, may be waiting for new treatment options, or may want to experiment with shifting their virus back to the "wild type" that is more drug-sensitive.
Doctors and patients should plan treatment interruptions. Viral load and T-cell levels should be carefully monitored. Just skipping doses has more risks and does not contribute to knowledge about HIV treatments.


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WHAT ARE THE RISKS?
The most obvious risks of an STI are that the viral load will climb and the T-cell count will drop. These risks are greatest for people whose virus is not under control. If you have only 50 T-cells, losing another 10 might have serious consequences.

Stopping and re-starting medications could make it easier for the virus to develop resistance to medications. Surprisingly, there is almost no evidence of resistance developing in people who took part in studies of STIs.

This risk may be greatest for people taking drugs like Efavirenz (Sustiva®) that stay in the body much longer than other antiviral drugs. They could be discontinued before other drugs in a regimen, but this has not been carefully studied.

Also, if the viral load increases while people are off medications, people might be more likely to transmit HIV infection to others. On the other hand, if they are off medications, they might be more likely to transmit the wild type virus, not drug-resistant virus.

People ending a treatment interruption might have a hard time re-starting medications.


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WHAT ARE THE POSSIBLE BENEFITS?
Ideally, an STI would have several benefits:

Stimulate the immune system. The best case is immune control of HIV without antiviral medications.
Allow patients to take less medication. This should reduce side effects and lower drug costs for individuals and public programs.


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WHAT DOES THE RESEARCH SHOW?
Many people who stop antiviral drugs feel better, at least for a short time. However, long-term benefits are unclear.

Primary infection: During an STI, viral loads go up and T-cell counts go down except for very rare exceptions. Researchers cannot predict who will control HIV without drugs.

Chronic infection: Again, viral loads go up and T-cell counts go down. Patients in this group who control HIV without antiviral medications are very rare. Researchers are adding immune-boosting therapies to treatment interruptions.

For a few drug-resistant patients, it seems that medications were not doing anything, because when they stopped, viral loads and t-cell counts didn't change very much. In some cases, HIV shifts back to a more "wild type" virus that is not resistant to antiviral medications. Scientists are not sure that this is a good thing, because the wild type virus is stronger than virus that is resistant to several drugs.


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THE BOTTOM LINE
HIV patients stop antiviral treatments for various reasons. In very rare cases, treatment interruption has led to immune system control of HIV without medications. However, there is no way to predict when this will happen.

If we can learn how to use treatment interruptions, patients might be able to take periods of time off of antiviral drugs. This could mean fewer side effects and lower drug costs. However, we will have to learn how to minimize drug resistance and transmission of HIV, and learn the best scheduling of treatment interruptions to avoid long term increases in viral load and decreases in T-cells.



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Revised August 30, 2001

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