Nucleoside reverse transcriptase inhibitor (NRTI) Pregnancy: More than 800 first-trimester and 1000 later-trimester outcomes indicate no malformative or foetal/neonatal effect; weigh antiretroviral benefit/risk when treating HIV in pregnancy.

Abacavir

Brand names: Ziagen

Abacavir is a nucleoside reverse transcriptase inhibitor (NRTI) used as part of combination antiretroviral therapy for HIV infection.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 600 mg

Route: Oral

Frequency: Once daily (600 mg) or 300 mg twice daily

For HIV infection, in combination with other antiretrovirals; for adults, adolescents and children weighing at least 25 kg. HLA-B*5701 status must be documented before starting and abacavir must never be initiated in HLA-B*5701-positive patients. Can be taken with or without food; tablets may be crushed if needed. Children <25 kg dosed by weight bands (450 mg daily for 20-<25 kg; 300 mg daily for 14-20 kg).

Dose adjustments

Renal

No dosage adjustment necessary in renal dysfunction; not recommended in end-stage renal disease.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to abacavir or to any of the excipients

Side effects

Nausea, vomiting, diarrhoea
Headache
Rash (without systemic symptoms)
Fever, lethargy, fatigue
Anorexia
Hypersensitivity reactions (may be life-threatening) - fever and/or rash with multi-organ involvement
Rare: pancreatitis; very rare: lactic acidosis, Stevens-Johnson syndrome, toxic epidermal necrolysis

Interactions

Methadone: an increased methadone dose may be required in a small number of patients
Riociguat: riociguat dose may need to be reduced (increased riociguat exposure)

Clinical monograph

How it works

Its intracellular triphosphate metabolite competitively inhibits HIV reverse transcriptase and terminates the growing viral DNA chain.

Prescribing in practice

A potentially fatal hypersensitivity reaction occurs almost exclusively in HLA-B*57:01-positive patients, so screen for this allele before starting and never rechallenge after suspected hypersensitivity.
Must always be used in combination with other antiretrovirals to avoid resistance.
An association with increased cardiovascular risk has been reported, so consider baseline cardiovascular risk as directed by current prescribing references.

Monitoring

Monitor for hypersensitivity reactions, virological response (HIV viral load and CD4 count) and cardiovascular risk factors.

Counselling the patient

Carry your hypersensitivity alert card and stop the drug and seek urgent help if you develop a reaction such as fever, rash, gastrointestinal or respiratory symptoms.
Never restart abacavir once a hypersensitivity reaction is suspected.
Take all your HIV medicines exactly as prescribed to keep the virus suppressed.

Evidence & guidelines

Routine HLA-B*57:01 screening to prevent hypersensitivity is supported by the PREDICT-1 study and is standard UK practice.

Reference: BHIVA Adult ART Guidelines 2022; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways