Dual NRTI combination (antiretroviral) Pregnancy: A large amount of data on pregnant women taking lamivudine or zidovudine (more than 3000 first-trimester outcomes each) indicates no malformative toxicity and a malformative risk is unlikely in humans; use of zidovudine in pregnancy with subsequent treatment of the newborn reduces maternal-foetal HIV transmission. Consider possible recurrence of hepatitis on lamivudine discontinuation in hepatitis co-infection. Breastfeeding: it is recommended that women living with HIV do not breast-feed their infants in order to avoid transmission of HIV.

Zidovudine with lamivudine

Brand names: Combivir

A fixed-dose combination of two nucleoside reverse transcriptase inhibitors (zidovudine and lamivudine) used as a backbone 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: One tablet (lamivudine 150 mg / zidovudine 300 mg)

Route: Oral

Frequency: Twice daily

Adults and adolescents weighing at least 30 kg: one tablet twice daily. Therapy should be initiated by a physician experienced in the management of HIV infection. May be given with or without food; tablets should ideally be swallowed without crushing, but may be crushed and added to a small amount of semi-solid food or liquid consumed immediately if the patient cannot swallow tablets. Paediatric dosing in the SPC is by weight band, not per kg: children 21-30 kg — one-half tablet in the morning and one whole tablet in the evening (if gastrointestinal intolerance occurs, an alternative schedule of one-half tablet three times daily may be tried); children 14-21 kg — one-half tablet twice daily. The fixed-dose tablet should not be used in children weighing less than 14 kg because doses cannot be appropriately adjusted for weight — use separate lamivudine and zidovudine formulations. Paediatric 14-30 kg dosing is based primarily on pharmacokinetic modelling; pharmacokinetic overexposure to zidovudine can occur, so close safety monitoring is warranted. Where dose reduction or discontinuation of one component is needed (e.g. haemoglobin below 9 g/dL or 5.59 mmol/L, or neutrophil count below 1.0 x 10^9/L), the fixed combination cannot be adjusted — use separate preparations of lamivudine and zidovudine. Elderly: no specific data; special care advised because of age-associated decline in renal function and altered haematological parameters.

Dose adjustments

Renal

Lamivudine and zidovudine concentrations rise in renal impairment due to decreased clearance; because the fixed combination cannot be dose-adjusted, separate preparations of lamivudine and zidovudine are recommended in severe renal impairment (creatinine clearance ≤30 mL/min). Similarly, use separate preparations in severe hepatic impairment.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substances or to any of the excipients
Abnormally low neutrophil count (<0.75 x 10^9/L)
Abnormally low haemoglobin (<7.5 g/dL or 4.65 mmol/L)

Side effects

Neutropenia and anaemia (both occasionally severe) and thrombocytopenia (uncommon); pure red cell aplasia (very rare)
Headache, insomnia (common)
Nausea, vomiting, abdominal pain or cramps, diarrhoea (common)
Cough, nasal symptoms (common)
Lactic acidosis, sometimes fatal, usually associated with severe hepatomegaly and hepatic steatosis (very rare)
Loss of subcutaneous fat (lipoatrophy), most evident in face, limbs and buttocks — discontinue if it develops; pancreatitis and rises in serum amylase (rare)

Interactions

Stavudine — concomitant use with zidovudine should be avoided (SPC §4.4, cross-referencing §4.5; the §4.5 interactions section was not captured in this source extract, so the interaction list is incomplete)

Clinical monograph

How it works

Both components are phosphorylated intracellularly to active triphosphates that competitively inhibit HIV reverse transcriptase and act as chain terminators, blocking viral DNA synthesis.

Prescribing in practice

Zidovudine commonly causes bone-marrow suppression (anaemia and neutropenia), so the full blood count must be monitored; both drugs carry a class risk of lactic acidosis and hepatomegaly with steatosis.
It must always be used as part of a fully suppressive combination regimen, never as monotherapy, to avoid resistance.
Lamivudine is also active against hepatitis B, so stopping therapy may precipitate a hepatitis flare in co-infected patients.

Monitoring

Monitor full blood count (particularly during early zidovudine therapy), liver function and HIV viral load and CD4 count.

Counselling the patient

Take every dose to keep the virus suppressed and prevent resistance.
Report unusual tiredness, breathlessness or pale skin which may indicate anaemia.
Seek urgent advice for severe nausea, abdominal pain or rapid deep breathing.

Evidence & guidelines

Zidovudine plus lamivudine is a long-established NRTI backbone, though newer regimens are now generally preferred in UK HIV guidelines.

Reference: BHIVA guidelines; 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