Abacavir with lamivudine and zidovudine

How it works

All three components are nucleoside analogues that are phosphorylated intracellularly and incorporated into viral DNA by reverse transcriptase, terminating chain elongation; zidovudine adds the characteristic risk of bone-marrow suppression.

Prescribing in practice

• Screen for HLA-B*57:01 and avoid in carriers or anyone with prior abacavir hypersensitivity because of the risk of a severe, potentially fatal reaction.
• The zidovudine component carries a notable risk of anaemia and neutropenia, so haematological monitoring is required and it is unsuitable where marrow reserve is poor.
• Triple-nucleoside regimens are generally less virologically robust than integrase- or protease-inhibitor-based regimens and are now reserved for selected situations only.

Monitoring

Monitor full blood count for zidovudine-related cytopenias along with viral load, CD4 count and renal and hepatic function.

Counselling the patient

• Report any rash, fever or hypersensitivity symptoms immediately and carry your alert card.
• Watch for unusual tiredness or breathlessness, which may indicate anaemia, and attend for blood tests.
• Take the tablet consistently and do not stop without specialist advice.

Evidence & guidelines

HLA-B*57:01 screening is mandated by the MHRA before abacavir use, and UK HIV guidelines now favour newer combinations over triple-nucleoside regimens for most patients.