Abacavir

Abacavir is a prescription medication used to treat human immunodeficiency virus (HIV) infection. Abacavir belongs to a group of drugs called nucleoside analogue reverse transcriptase inhibitors (NRTIs). It works by preventing the virus from multiplying.

This medication comes in tablet and liquid forms and is usually taken once or twice daily.

Common side effects of abacavir include nausea, vomiting, tiredness, and headaches.

Some patients carry a version of a gene (called an allele) that makes them more susceptible to having a severe allergic reaction to abacavir. This allele is called human leukocyte antigen-B*5701 (HLA-B*5701). This allele codes for a protein that is involved in your body's immune response to infections and foreign bodies.

HLA-B*5701 testing is done to determine if you are at a high risk of having a severe, life-threatening allergic reaction to abacavir. If you have this HLA-B*5701 allele, your doctor may decide not to treat you with abacavir. If you test negative for this mutation, you may still experience an allergic reaction, but it will be less likely than if you tested positive for the mutation.

The HLA-B*5701 protein is involved in your body'a immune response. Having this protein puts your immune system into overdrive, which puts you at an increased risk of having an allergic reaction to abacavir.

Abacavir is a prescription medicine used to treat human immunodeficiency virus (HIV) infection. Abacavir is always used with other anti-HIV medicines. 

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Abacavir may be found in some form under the following brand names:

• Epzicom

• Trizivir

• Ziagen

Abacavir can cause the following serious side effects:

• Serious allergic reaction that can cause death. (See "Drug Precautions".)
• Lactic acidosis with liver enlargement (hepatomegaly) that can cause death. (See "Drug Precautions".)
• Changes in immune system. When you start taking HIV medicines, your immune system may get stronger and could begin to fight infections that have been hidden in your body, such as pneumonia, herpes virus, or tuberculosis. If you have new symptoms after starting your HIV medicines, be sure to tell your doctor.
• Changes in body fat. These changes have happened in patients taking antiretroviral medicines like abacavir. The changes may include an increased amount of fat in the upper back and neck (“buffalo hump”), breast, and around the back, chest, and stomach area. Loss of fat from the legs, arms, and face may also happen. The cause and long-term health effects of these conditions are not known.

Some HIV medicines including abacavir may increase your risk of heart attack. If you have heart problems, smoke, or suffer from diseases that increase your risk of heart disease such as high blood pressure, high cholesterol, or diabetes, tell your doctor.

The most common side effects of abacavir include nausea, vomiting, tiredness, headache, diarrhea, trouble sleeping, fever and chills, and loss of appetite. Most of these side effects did not cause people to stop taking abacavir.

This list of side effects is not complete. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Tell your doctor about all the medicines you take, including prescription and nonprescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

• Methadone
• Epzicom (abacavir sulfate and lamivudine) and Trizivir (abacavir sulfate, lamivudine, and zidovudine).

This is not a complete list of abacavir drug interactions. Ask your doctor or pharmacist for more information.

The most important information you should know about abacavir:

• Serious Allergic Reaction to Abacavir. Abacavir is also contained in Epzicom and Trizivir. Patients taking abacavir may have a serious allergic reaction (hypersensitivity reaction) that can cause death. Your risk of this allergic reaction is much higher if you have a gene variation called HLA-B*5701 than if you do not. Your doctor can determine with a blood test if you have this gene variation. If you get a symptom from 2 or more of the following groups while taking abacavir, call your doctor right away to determine if you should stop taking this medicine.

Symptoms:

Group 1: Fever

Group 2: Rash

Group 3: Nausea, vomiting, diarrhea, abdominal (stomach area) pain 

Group 4: Generally ill feeling, extreme tiredness, or achiness

Group 5: Shortness of breath, cough, sore throat

A list of these symptoms is on the Warning Card your pharmacist gives you. Carry this Warning Card with you.

If you stop abacavir because of an allergic reaction, NEVER take abacavir or any other abacavir-containing medicine (Epzicom and Trizivir) again. If you take abacavir or any other abacavir-containing medicine again after you have had an allergic reaction, WITHIN HOURS you may get life-threatening symptoms that may include very low blood pressure or death.

If you stop abacavir for any other reason, even for a few days and you are not allergic to abacavir, talk with your doctor before taking it again. Taking abacavir again can cause a serious allergic or life-threatening reaction, even if you never had an allergic reaction to it before. If your doctor tells you that you can take abacavir again, start taking it when you are around medical help or people who can call a doctor if you need one.

• Lactic Acidosis. Some human immunodeficiency virus (HIV) medicines, including abacavir, can cause a rare but serious condition called lactic acidosis with liver enlargement (hepatomegaly). Nausea and tiredness that don't get better may be symptoms of lactic acidosis. In some cases this condition can cause death. Women, overweight people, and people who have taken HIV medicines like abacavir for a long time have a higher chance of getting lactic acidosis and liver enlargement. Lactic acidosis is a medical emergency and must be treated in the hospital.

Abacavir can have other serious side effects. Be sure to read the section entitled "Side Effects".

Do not take abacavir if you:

• have ever had a serious allergic reaction (a hypersensitivity reaction) to abacavir or any other medicine that has abacavir as one of its ingredients (Epzicom and Trizivir).
• have a liver that does not function properly.

Medicines can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of abacavir, there are no specific foods that you must exclude from your diet when receiving abacavir.

Before starting abacavir, tell your doctor about all of your medical conditions, including if you:

• have been tested and know whether or not you have a particular gene variation called HLA-B*5701.
• are pregnant or planning to become pregnant. It is not known if abacavir will harm your unborn child. You and your doctor will need to decide if abacavir is right for you. If you use abacavir while you are pregnant, talk to your doctor about how you can be on the Antiviral Pregnancy Registry for abacavir.
• are breastfeeding. It is not known if abacavir can be passed to your baby in your breast milk and whether it could harm your baby. Also, mothers with HIV should not breastfeed because HIV can be passed to the baby in the breast milk.
• have liver problems.
• have heart problems, smoke, or suffer from diseases that increase your risk of heart disease such as high blood pressure, high cholesterol, or diabetes.

Tell your doctor about all the medicines you take, including prescription and nonprescription medicines, vitamins, and herbal supplements.

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

This medication falls into category C. In animal studies, pregnant animals were given this medication and had some babies born with problems. No well-controlled studies have been done in humans. Therefore, this medication may be used if the potential benefits to the mother outweigh the potential risks to the unborn child.

If you take this medication while you are pregnant, talk to your healthcare provider about how you can take part in the Pregnancy Registry. The purpose of the pregnancy registry is to collect information about the health of you and your baby.

Do not breastfeed while receiving this medication. It is not known if abacavir can be passed to your baby in your breast milk and whether it could harm your baby. Also, mothers with HIV should not breastfeed because HIV can be passed to the baby in the breast milk.

• Take abacavir by mouth exactly as your doctor prescribes it. Your doctor will tell you the right dose to take. The usual doses are 1 tablet twice a day or 2 tablets once a day. Do not skip doses.
• Children aged 3 months and older can also take abacavir. The child's healthcare professional will decide the right dose and formulation based on the child's weight. The dose should not exceed the recommended adult dose.
• You can take abacavir with or without food.
• If you miss a dose of abacavir, take the missed dose right away. Then, take the next dose at the usual time.
• Do not let your abacavir run out.
• Starting abacavir again can cause a serious allergic or life-threatening reaction, even if you never had an allergic reaction to it before. If you run out of abacavir even for a few days, you must ask your doctor if you can start abacavir again. If your doctor tells you that you can take abacavir again, start taking it when you are around medical help or people who can call a doctor if you need one.
• If you stop your anti-HIV drugs, even for a short time, the amount of virus in your blood may increase and the virus may become harder to treat.
• If you take too much abacavir, call your doctor or poison control center right away.

What you should avoid while taking abacavir:

• Do not take Epzicom (abacavir sulfate and lamivudine) or Trizivir (abacavir sulfate, lamivudine, and zidovudine) while taking abacavir.

Avoid doing things that can spread HIV infection, as abacavir does not stop you from passing the HIV infection to others.

• Do not share needles or other injection equipment.
• Do not share personal items that can have blood or body fluids on them, like toothbrushes and razor blades.
• Do not have any kind of sex without protection. Always practice safe sex by using a latex or polyurethane condom or other barrier method to lower the chance of sexual contact with semen, vaginal secretions, or blood.
• Do not breastfeed. It is not known if abacavir can be passed to your baby in your breast milk and whether it could harm your baby. Also, mothers with HIV should not breastfeed because HIV can be passed to the baby in the breast milk.

Take this medication exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

The dose your doctor recommends may be based on the following:

• the condition being treated
• other medical conditions you have
• other medications you are taking
• how you respond to this medication
• your weight
• your age

Adult Patients

The recommended oral (by mouth) dose of abacavir for adults is 600 mg daily, administered as either 300 mg twice daily or 600 mg once daily, in combination with other antiretroviral agents.

Pediatric Patients

If you take too much abacavir, call your doctor or poison control center right away.

If abacavir is administered by a healthcare provider in a medical setting, it is unlikely that an overdose will occur. However, if overdose is suspected, seek emergency medical attention.

• Store abacavir at room temperature, between 68° to 77°F (20° to 25°C). Do not freeze abacavir.
• Keep abacavir and all medicines out of the reach of children.

WARNING: RISK OF HYPERSENSITIVITY REACTIONS, LACTIC ACIDOSIS, AND SEVERE HEPATOMEGALY

Serious and sometimes fatal hypersensitivity reactions have been associated with abacavir sulfate.

Hypersensitivity to abacavir is a multi-organ clinical syndrome usually characterized by a sign or symptom in 2 or more of the following groups: (1) fever, (2) rash, (3) gastrointestinal (including nausea, vomiting, diarrhea, or abdominal pain), (4) constitutional (including generalized malaise, fatigue, or achiness), and (5) respiratory (including dyspnea, cough, or pharyngitis). Discontinue abacavir as soon as a hypersensitivity reaction is suspected.

Patients who carry the HLA-B*5701 allele are at high risk for experiencing a hypersensitivity reaction to abacavir sulfate. Prior to initiating therapy with abacavir, screening for the HLA-B*5701 allele is recommended; this approach has been found to decrease the risk of hypersensitivity reaction. Screening is also recommended prior to reinitiation of abacavir in patients of unknown HLA-B*5701 status who have previously tolerated abacavir. HLA-B*5701-negative patients may develop a suspected hypersensitivity reaction to abacavir; however, this occurs significantly less frequently than in HLA-B*5701-positive patients.

Regardless of HLA-B*5701 status, permanently discontinue abacavir sulfate if hypersensitivity cannot be ruled out, even when other diagnoses are possible.

Following a hypersensitivity reaction to abacavir sulfate, NEVER restart abacavir sulfate or any other abacavir-containing product because more severe symptoms can occur within hours and may include life-threatening hypotension and death.

Reintroduction of abacavir sulfate or any other abacavir-containing product, even in patients who have no identified history or unrecognized symptoms of hypersensitivity to abacavir sulfate therapy, can result in serious or fatal hypersensitivity reactions. Such reactions can occur within hours.

Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogues alone or in combination, including abacavir sulfate and other antiretrovirals.