Last update: October 2008
Ziagen – brand name
abacavir – generic name
Ziagen belongs to a class of HIV drugs called nucleoside reverse transcriptase inhibitors (NRTIs), also known as nucleoside analogs or “nukes.”
The NRTIs block reverse transcriptase, a protein that HIV needs to make more copies of itself. This may slow down HIV disease.
The Food and Drug Administration (FDA) has approved Ziagen for use in combination with other HIV drugs for the treatment of HIV infection in adults and children over three months of age.
Ziagen comes in:
- 300 milligram (mg) tablets
The usual dose for adults is 600 mg, taken as either:
- One 300 mg tablet twice a day
- Two 300 mg tablets once a day
Ziagen must be used with other HIV medications to treat HIV.
You can take Ziagen with food or on an empty stomach, but taking it with food may cut down on nausea or other side effects.
Speak to your doctor if you have liver or kidney problems.
Check with your child’s doctor for children’s dosing.
Many people use Ziagen in combination pills that also contain other NRTI drugs:
- Trizivir: Ziagen plus Epivir (lamivudine or 3TC) plus Retrovir (zidovudine or AZT)
- Epzicom: Ziagen plus Epivir
Do not take Ziagen if you have ever experienced a hypersensitivity reaction to Ziagen, Trizivir, or Epzicom.
As with all HIV drugs, it is important to take Ziagen as prescribed. Missing or skipping doses can cause your blood levels of the drug to fall too low and resistance can develop. When your virus becomes resistant to an HIV medication, that drug may stop working.
Ziagen can be used if you’re just starting on treatment.
Ziagen can be used if you’ve been on treatment before, however, it will probably not work as well for people who are already resistant to Retrovir and Epivir.
Your doctor can run a resistance test to help determine whether Ziagen is likely to work for you.
Ziagen crosses the blood-brain barrier (which protects the brain and spinal cord), so it may be able to fight HIV in the brain.
If your virus develops resistance to the drugs in Ziagen then it may stop working or not work as well for you. You also may not get as much benefit from the other NRTIs.
Sometimes taking more than one medication can cause drug interactions. Taking certain drugs (including methadone) with Ziagen might change the amount of each drug in your blood. Your doctor may need to adjust the doses of your drugs to avoid under- or overdosing.
Ziagen plus Epivir plus Viread (tenofovir) should not be used together.
Be sure your doctor knows about all the medications you are taking (including over-the-counter, prescription, street drugs, and herbs), even if you only use them occasionally.
For more information and additional resources to check interactions between the particular drugs you are taking, see our info sheet on drug interactions.
Ziagen is generally well tolerated. If you do experience any side effects from Ziagen, they are likely to be temporary and go away as your body adjusts to the medication. If you experience any of the side effects listed below, call your doctor for advice. Do not just stop taking your medication.
- Loss of appetite
- Fatigue (unusual tiredness)
- Insomnia (trouble falling or staying asleep)
More serious side effects:
- Hypersensitivity reaction: About 8 percent of people who take Ziagen develop a very serious, potentially fatal side effect called a hypersensitivity (allergic) reaction. Signs to watch for include: fever; skin rash; severe nausea, vomiting, or abdominal pain; cough, sore throat, or difficulty breathing. If you experience any of these symptoms, call your doctor immediately. Your doctor can perform a special blood test to determine if you are among the 8% of people who should not take Ziagen; the test is for a specific genetic marker called HLA-B*5701. If your doctor stops your Ziagen because of a suspected hypersensitivity reaction, do not take Ziagen, Trizivir, or Epzicom ever again. All fatal hypersensitivity reactions have happened when someone re-started the drug after discontinuation.
- An increase of lactic acid in the blood ( lactic acidosis), an enlarged and fatty liver and liver failure, have been reported in people using NRTIs. Lactic acidosis is a rare but potentially fatal side effect. Symptoms include nausea, vomiting, or stomach pain; feeling very weak and tired; shortness of breath.
- Lipodystrophy, which may include elevated blood sugar (glucose), elevated lipid levels ( cholesterol and triglycerides), and fat gain or loss in certain areas. The exact causes of lipodystrophy are not known, but may include HIV and/or HIV drugs. It is unclear if Ziagen will cause or impact symptoms of lipodystrophy. For more information on lipodystrophy, see our info sheet.
- Studies do not agree on whether taking Ziagen can increase your risk of heart disease. If you think you might be at increased risk of heart disease, you should talk to your doctor about whether you should take Ziagen.
If you are experiencing persistent, unusual, or serious side effects, call your doctor right away.
Ziagen has been studied in both men and women. Its effectiveness and side effects seem very similar in both men and women. But some research suggests that women are more likely than men to develop liver problems and the rare but very serious side effect, lactic acidosis, while taking NRTI drugs.
Ziagen received accelerated approval based in part on three pivotal studies. Study CNA3003 included 173 participants, of whom 24 percent (or about 42) were women. This study showed that people who took Ziagen plus Retrovir plus Epivir as their first treatment regimen were more than twice as likely to achieve an undetectable viral load as people who took just Retrovir plus Epivir.
Study CNA3005 compared Ziagen to Crixivan (indinavir), both used with Retrovir and Epivir. This study included 562 participants being treated for the first time, of whom 13 percent (or about 73) were women. People in the Ziagen group and those in the Crixivan group were about equally likely to achieve an undetectable viral load, and CD4 cell increases were similar in both groups. However, there were more side effects in the Crixivan group. (Note: There were some problems with the design of this study.)
A third trial, CNA3006, tested Ziagen in people who had a history of previous treatment. This study was unusual for a pivotal trial because it was done in children, of whom 56 percent, or about 366, were girls. In this study 18 percent of those who took Ziagen plus Retrovir plus Epivir achieved an undetectable viral load, compared with only 2 percent of those who took just Retrovir plus Epivir.
A pharmacokinetic study by GlaxoSmithKline found no differences related to sex or body weight in how Ziagen is processed in the body (this study included 7 women and 34 men).
In July 2003, GlaxoSmithKline announced that it has stopped a trial (ESS30009) early after it showed that a once-daily triple NRTI regimen of Ziagen plus Epivir plus Viread did not work as well as Ziagen plus Epivir plus Viracept (nelfinavir) in people who had not taken HIV drugs before. At the International AIDS Society conference in July 2003, researchers reported that 58 percent of the 19 participants (including 3 women) in one study did not respond to Ziagen plus Epivir plus Viread. This triple-NRTI regimen does not appear powerful enough to suppress HIV in many people, and the virus can quickly develop resistance to these drugs when used together.
In terms of side effects, several studies have shown that Ziagen is less likely than protease inhibitors to increase blood fat levels. The ESS4002 study is notable because it included half women and about 40 percent each of African Americans and Hispanics (out of a total of 258 participants).
Study ESS4002 compared Ziagen plus Retrovir plus Epivir to Viracept plus Retrovir plus Epivir to Viracept plus Zerit (stavudine or d4T) plus Epivir. Overall, blood fat levels were lower in people who took the regimen that included Ziagen compared with those who took the regimen that included Viracept. But among those who took Viracept, women had higher levels of LDL (“bad cholesterol”) at 96 weeks than men.
Another study called TRIZAL, which had 209 participants, including 20 percent (or about 41) women, showed that switching to Ziagen from a protease inhibitor or a non-nucleoside reverse transcriptase inhibitor (NNRTI) reduced cholesterol levels and may have improved lipodystrophy.
An analysis of more than 5,300 people using Ziagen in 25 different clinical trials did not find any difference in the rate of hypersensitivity in women and men. However, most of the rare cases of lactic acidosis seen in people taking Ziagen have been in women, especially women who were overweight.
Studies have shown that pregnant women who use HIV drugs can greatly reduce the risk of passing HIV on to their babies. There have been no formal studies on the use of Ziagen during pregnancy, however, there have been several case studies that showed pregnant women who took Ziagen delivered healthy, full-term babies.
Check with your doctor about the best treatment options for you and your baby if you are thinking of getting pregnant.
Click this link for more information about pregnancy.
People who are starting HIV treatment for the first time may develop Immune Reconstitution Syndrome or IRS (also called Immune Reconstitution Inflammatory Syndrome or IRIS). IRS can happen as a result of the immune system getting stronger and responding to an HIV-related infection such as Mycobacterium avium infection (MAC), cytomegalovirus (CMV), Pneumocystis jirovecii pneumonia (PCP), or tuberculosis (TB). People may have been treated for these infections in the past or not even know they have them. If you notice any unusual symptoms soon after starting HIV drugs for the first time, let your doctor know right away so you can be evaluated and, if necessary, treated