Pharmacology · Nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs)

Abacavir !

An NRTI antiretroviral. Before use, patients are tested for HLA-B*5701, which predicts a severe, potentially fatal hypersensitivity reaction.

Updated 2026-11-01

Class: Nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs)
Enzyme: HIV-1 reverse transcriptase
ATC code: J05AF06
WHO Model List of Essential Medicines

Also called: ABC

Mechanism of action

A guanosine analogue. Inside the cell it becomes carbovir triphosphate, which competes with natural dGTP; reverse transcriptase incorporates it into viral DNA and the chain stops. Hypersensitivity happens because abacavir sits in the groove of the HLA-B*57:01 molecule and changes the peptides it presents, so T cells see them as foreign.

Cellular kinases convert it to carbovir triphosphate
It competes with dGTP at reverse transcriptase
It is built into viral DNA and ends the chain

Pharmacokinetics

Absorption: Good oral absorption (tablet bioavailability about 83%); food does not change it much
Metabolism: Liver, by alcohol dehydrogenase and glucuronidation; it barely uses cytochrome P450
Elimination: Inactive metabolites, mainly in urine

Indications

HIV-1 infection, combined with other antiretrovirals HIV infection and AIDS →

Adverse effects

Common

Nausea and vomiting
Headache
Tiredness
Insomnia

Contraindications

Carrier of the HLA-B*5701 allele
Previous hypersensitivity to abacavir
Moderate or severe hepatic impairment

Key interactions

Alcohol (ethanol): They share alcohol dehydrogenase: ethanol slows abacavir elimination and raises exposure
Methadone: Some patients may need a methadone adjustment

What is monitored

HLA-B*5701 test before starting
Hypersensitivity symptoms, especially in the first weeks
Viral load and CD4
Cardiovascular risk

Administration and safety

Given by mouth, as a tablet or solution
After a hypersensitivity reaction, no abacavir-containing product is ever restarted: the reaction can kill within hours
Check whether the patient already gets abacavir inside a fixed-dose combination so it is not duplicated

Nursing care

Confirm the negative HLA-B*5701 result in the record before the first dose
Teach the warning symptoms (fever, rash, nausea, abdominal pain, cough, shortness of breath) and to seek care at once
Explain that it must not be stopped or restarted on the patient's own
Hand over the product's warning card, if there is one

Pregnancy and breastfeeding

Antiretroviral pregnancy registry data show no more birth defects than in the general population.

Test yourself

Think of the answer, then tap the question to see it.

Which test is done before starting abacavir?

Testing for the HLA-B*5701 allele; carriers have a high risk of severe hypersensitivity and do not receive the drug.

A patient stopped abacavir because of a probable hypersensitivity reaction. Can it be restarted?

No. Restarting it can cause a more severe reaction and death within hours.

Why does alcohol raise abacavir levels?

Both are metabolised by alcohol dehydrogenase; ethanol competes and slows abacavir elimination.

Add to my cards (3)

HIV infection and AIDS

← Back to the class: Nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - ABACAVIR tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); Abacavir: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).

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Representative model, for educational purposes only.