Abacavir: HIV-1 treatment, dosing, and side effects
Last updated September 6, 2026.
**Abacavir is a prescription antiretroviral medicine, a nucleoside reverse transcriptase inhibitor (NRTI), used with other HIV medicines to treat HIV-1 infection.** HIV needs an enzyme called reverse transcriptase to copy its genetic material inside your cells. Abacavir blocks that enzyme, so the virus makes fewer copies of itself and the amount of virus in your blood drops. The single most important safety point is that you must be tested for the HLA-B*5701 gene before your first dose, because people who carry it have a high risk of a serious hypersensitivity reaction, and anyone who has ever had that reaction to abacavir must never take it again.
What does it treat?
Abacavir treats HIV-1 infection in adults and children. It is never used alone: it is always part of a combination regimen aimed at pushing your viral load down to undetectable and letting your CD4 count recover, which prevents opportunistic infections and progression to AIDS. It does not cure HIV and does not stop you from passing HIV to others on its own, though staying undetectable on treatment does prevent sexual transmission. Many people take it inside a single fixed-dose tablet rather than by itself: abacavir plus lamivudine (Epzicom), abacavir plus dolutegravir plus lamivudine (Triumeq), or abacavir plus lamivudine plus zidovudine (Trizivir). If you take one of those, you are already taking abacavir and must not add a separate abacavir tablet.
How do you take it?
Abacavir comes as 300 mg tablets and as a 20 mg/mL oral solution, sold as Ziagen and as generics. The usual adult dose is 600 mg a day, taken either as one 300 mg tablet twice daily or as 600 mg once daily, and 600 mg a day is the ceiling for adults. Children are dosed by weight or body surface area, so follow the exact amount your clinician gives you. You can take it with or without food. If you have mild liver disease (Child-Pugh 5 to 6), the dose drops to 200 mg twice daily using the oral solution, and abacavir is not used at all in moderate or severe liver disease. If you miss a dose, take it as soon as you remember, unless it is almost time for the next one, in which case skip the missed dose and go back to your schedule; never double up. Stop abacavir and call your clinician right away if you develop fever, rash, nausea, vomiting, diarrhea, stomach pain, extreme tiredness, cough, sore throat, or shortness of breath, and do not restart it on your own, because restarting after a hypersensitivity reaction can cause a rapid, life-threatening drop in blood pressure.
Side effects to know
- Common: Common effects include nausea, vomiting, headache, tiredness, trouble sleeping, and unusual dreams, and these often settle over the first few weeks.
- Serious: Stop abacavir and get medical help the same day for a hypersensitivity reaction: fever, rash, nausea or vomiting or diarrhea or belly pain, severe tiredness or aching, cough, sore throat, or trouble breathing, especially two or more of these groups together in the first six weeks. Also get urgent care for signs of lactic acidosis or liver injury, including deep or rapid breathing, unusual muscle pain, feeling cold or lightheaded, yellowing of your eyes or skin, dark urine, or pain over your upper right abdomen.
Who should not take it?
Do not take abacavir if you carry the HLA-B*5701 gene, if you have ever had a hypersensitivity reaction to abacavir or any abacavir-containing product (Ziagen, Epzicom, Triumeq, Trizivir), or if you have moderate or severe liver disease. Talk with a clinician first if you have any liver disease, hepatitis B or hepatitis C, kidney disease, a history of heart disease or several cardiac risk factors, or a history of pancreatitis. Tell your clinician about methadone, since abacavir can make your body clear methadone faster and the methadone dose may need adjusting, and about every other HIV medicine you take so you do not double up on abacavir or lamivudine. Alcohol raises abacavir blood levels by about 41 percent and adds its own strain on your liver, so keep drinking light or skip it, and be honest with your clinician about how much you drink. Abacavir is used during pregnancy when needed and current FDA labeling reports no drug-associated birth defect risk; if you are pregnant or planning a pregnancy, stay on treatment and tell your clinician so your regimen and monitoring can be set up. In the United States, labeling advises against breastfeeding because HIV can pass to the baby through breast milk, so discuss feeding plans before delivery.
When is it an emergency?
Call 911 now if you collapse, faint, have trouble breathing, have swelling of the face, lips, or throat, or have a widespread rash with blistering or peeling skin, which can signal anaphylaxis or a severe skin reaction. Call 911 or go to an emergency room for signs of lactic acidosis or serious liver injury: fast or deep breathing you cannot control, severe muscle aching, feeling very cold or weak, a fast or irregular heartbeat, severe stomach pain with vomiting, or yellow eyes or skin. If you took too much abacavir or someone else took your medicine, call Poison Control at 1-800-222-1222 right away, even if you feel fine; there is no specific antidote and they will tell you what to watch for. Never take another abacavir dose after a suspected hypersensitivity reaction, even if you feel better, because the next dose can drop your blood pressure dangerously within hours.
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Common questions
What is the maximum dose of abacavir I can take in a day?
For adults, 600 mg a day is the ceiling. That is taken either as 300 mg twice daily or as 600 mg once daily, and both schedules work equally well for most people. Taking more does not suppress HIV faster and raises your risk of side effects. If you have mild liver disease, the dose is lower at 200 mg twice daily using the oral solution. Children are dosed by weight, so use the exact amount and measuring device your clinic gives you.
Can I drink alcohol while taking abacavir?
There is no absolute ban, but alcohol raises abacavir levels in your blood by about 41 percent because it slows how your body clears the drug. Alcohol also stresses your liver, and liver problems are one of the things your clinician is already monitoring on this medicine. Light or occasional drinking is usually manageable; regular heavy drinking is not. Tell your clinician honestly how much you drink so liver tests can be scheduled sensibly. If you have hepatitis B or C or any liver disease, the safest answer is not to drink.
Is abacavir safe during pregnancy or while breastfeeding?
Abacavir is used in pregnancy when it is the right regimen for you, and current FDA labeling reports no drug-associated risk of birth defects from human data. Staying on HIV treatment during pregnancy protects your health and sharply lowers the chance of passing HIV to your baby, so do not stop on your own if you find out you are pregnant. Tell your clinician early so your regimen, viral load checks, and delivery plan can be arranged. For feeding, US labeling advises against breastfeeding because HIV can pass through breast milk. Talk this through before delivery so you have a plan in place.
Do I need to take abacavir with food?
No. Abacavir can be taken with or without food, and meals do not meaningfully change how much drug reaches your bloodstream. If it upsets your stomach, taking it with a snack often helps. What matters much more is taking it at the same times every day so your levels stay steady. If you take a combination tablet such as Triumeq or Epzicom, check that product's instructions too, since other ingredients can have their own timing rules around antacids, calcium, or iron.
What are the signs of an abacavir hypersensitivity reaction?
The classic pattern is fever, a rash, stomach symptoms like nausea, vomiting, diarrhea, or belly pain, severe tiredness or body aches, and breathing symptoms like cough, sore throat, or shortness of breath. Two or more of those groups appearing together, usually within the first six weeks, is the pattern clinicians act on. Stop the medicine and contact your clinician the same day. Do not take another dose while you wait, even if the symptoms ease, because restarting after a hypersensitivity reaction can cause a rapid and dangerous drop in blood pressure. Once you have had this reaction, abacavir and every abacavir-containing product are off the table for life.
What should I do if I take too much abacavir?
Call Poison Control at 1-800-222-1222 right away, even if you feel completely fine. There is no specific antidote for abacavir, and treatment is supportive, so the sooner they know the amount and timing, the better their advice. Have the bottle with you so you can read off the strength and how many tablets are missing. Call 911 instead if the person collapses, cannot breathe, or is confused or unresponsive. If you accidentally took a double dose, do not take the next scheduled dose without checking first.
What medicines and other drugs interact with abacavir?
Methadone is the main one on the label: abacavir speeds up how fast your body clears methadone, so your methadone dose may need to go up. Alcohol raises abacavir levels by about 41 percent. The most common real-world problem is accidental doubling, which happens when someone takes plain abacavir on top of a combination tablet like Epzicom, Triumeq, or Trizivir that already contains it. Bring a full list of your prescriptions, over-the-counter products, and supplements to every visit. Also flag any hepatitis B treatment, since stopping certain HIV medicines can trigger a hepatitis flare.