Abacavir Hypersensitivity

Is Testing Right for Me? I Have My Test Results

Abacavir Hypersensitivity

What Is Abacavir?

Abacavir is used along with other medicines to treat human immunodeficiency virus (HIV) infection. Abacavir belongs to a group of HIV drugs that work by stopping the virus from multiplying. Abacavir is an effective drug against HIV and is less toxic in the long-term than some other similar drugs.

Abacavir-containing Drugs
Generic names Brand names
AbacavirZiagen®
Abacavir + lamivudineEpzicom®
Abacavir + lamivudine + zidovudineTrizivir®

Allergic Reaction to Abacavir

Most people can take abacavir safely, but some people are very sensitive to abacavir. They can have a severe allergic reaction when they take the drug. For some people, the allergic reaction is life-threatening. Signs and symptoms of an allergic reaction can include:

  • Fever
  • Rash
  • Generally feeling ill or very tired
  • Gastrointestinal problems (nausea, vomiting, diarrhea, stomach pain)
  • Airway problems (shortness of breath, cough, sore throat)

If you are taking abacavir and are experiencing signs of an allergic reaction, you should call your doctor immediately. Your doctor may tell you to stop taking abacavir. If you have an allergic reaction to abacavir, you should never take a medicine that contains abacavir again.

Next: What Causes Allergic Reactions to Abacavir?

Why are you considering HLA-B*5701 testing for abacavir hypersensitivity?

I'm considering starting an abacavir drug to treat HIV infection.

I've taken an abacavir drug in the past and am considering restarting therapy.

I'm currently taking an abacavir drug and I'm not having any problems with it.

I'm currently taking an abacavir drug and I'm having side effects.

None of these.

HLA-B*5701 testing may be useful for you. Testing is recommended for  anyone who is starting treatment with these drugs. Testing can identify people who have a high chance of having a severe allergic reaction to abacavir. These people should not be treated with abacavir drugs.

If you have positive test results before you start abacavir therapy, your doctor may decide to treat you with a different drug instead.

Possible Test Results and How They May Impact You

Test Result Category Chance To Get This Result
What This Result Means
HLA-B*5701 negative ~95%
  • You have a lower chance for an allergic reaction.
  • You can take a drug that contains abacavir.
  • You'll need regular monitoring for an allergic reaction because this result doesn't rule out the chance you could have side effects.
HLA-B*5701 positive ~5%
  • You have a higher chance for an allergic reaction.
  • You shouldn't take a drug that contains abacavir.
  • Your doctor may decide to treat you with a different drug instead.

HLA-B*5701 testing may be useful for you. Testing is recommended for anyone restarting treatment with these drugs. If you did not have testing when you took the abacavir drug before, testing may be useful for you now, even if you had no problems last time you took an abacavir drug. Some people can have a serious allergic reaction when they restart treatment even if they didn't have a reaction before. Testing can identify people who have a high chance of having a severe allergic reaction to abacavir. These people should not be treated with abacavir drugs.

If you have a positive test result before you restart abacavir therapy, your doctor may decide to treat you with a different drug instead.

Possible Test Results and How They May Impact You

Test Result Category Chance To Get This Result
What This Result Means
HLA-B*5701 negative ~95%
  • You have a lower chance for an allergic reaction.
  • You can take a drug that contains abacavir.
  • You'll need regular monitoring for an allergic reaction because this result doesn't rule out the chance you could have side effects.
HLA-B*5701 positive ~5%
  • You have a higher chance for an allergic reaction.
  • You should not take a drug that contains abacavir.
  • Your doctor may decide to treat you with a different drug instead.

HLA-B*5701 testing may not be useful for you at this time. If you're currently taking an abacavir drug and aren't experiencing any signs of an allergic reaction, testing may not be useful for you at this time. Most people who have an allergic reaction have signs of the reaction within the first six weeks of taking the drug. If you had no early signs of an allergic reaction, you probably won't have one. However, you should still be monitored regularly for possible signs of an allergic reaction.

If at some point in the future you stop taking abacavir and then later want to start it again, testing may be useful to you before you restart. Some people can have a serious allergic reaction when they take abacavir again after stopping treatment -- even if they didn't seem to have a reaction before. Testing is recommended before restarting treatment with these drugs.

If you are taking abacavir and are experiencing signs of an allergic reaction you should call your doctor immediately. Your doctor may tell you to stop taking abacavir. If you have an allergic reaction to abacavir, you should never take a medicine that contains abacavir again.

There may not be a strong reason for you to have HLA-B*5701 testing, but you should ask your doctor. If you have the HLA-B*5701 variant, it may help explain your reaction and support the decision to stop treatment. However, even if you do not have the variant, if you are having an allergic reaction, you should stop taking the drug and not restart it.

Possible Test Results and How They May Impact You

Test Result Category Chance To Get This Result
What This Result Means
HLA-B*5701 negative ~95%
  • You have a lower chance for an allergic reaction.
  • Your symptoms may not be due to your abacavir treatment.
  • You could still be having an allergic reaction to abacavir. If your doctor thinks that you are having an allergic reaction you should stop taking abacavir and never take it again.
  • Your doctor may decide to treat you with a different drug instead.
HLA-B*5701 positive ~5%
  • You have a higher chance for an allergic reaction.
  • You should stop taking abacavir and never take it again.
  • Your doctor may decide to treat you with a different drug instead.

You should talk to your doctor about whether genetic testing would change your healthcare. If it would not affect your doctor's decisions, then testing is probably not useful for you.

HLA-B*5701 testing may not be useful for you. The main reasons for testing are listed in Who Should Consider Testing. Testing is not recommended for people who aren't starting or restarting an abacavir drug.

If you have a reason for testing that isn't covered here, talk to your doctor or a genetic counselor about whether testing might be useful for you.