Pharmacology · Nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs)
Zidovudine !
The first antiretroviral (AZT). Little used in adults today because of bone marrow toxicity, but still part of newborn prophylaxis.
Updated 2026-11-01
Also called: AZT, azidotimidina, ZDV
The figure shows zidovudine triphosphate (AZT-TP), the active form, in the polymerase site of HIV-1 reverse transcriptase with DNA.
Mechanism of action
A thymidine analogue with an azido group instead of the 3'-hydroxyl. It is phosphorylated to zidovudine triphosphate, which competes with dTTP; incorporated into viral DNA, it ends the chain. It also partly inhibits human polymerases, especially the mitochondrial one, which explains myopathy and marrow toxicity.
- It is phosphorylated to zidovudine triphosphate
- It competes with dTTP at reverse transcriptase
- The azido group blocks DNA chain extension
Pharmacokinetics
- Metabolism
- Glucuronidation in the liver to an inactive metabolite
- Elimination
- Zidovudine and its glucuronide leave in urine; they build up in severe kidney failure
Indications
- HIV-1 infection, combined with other antiretrovirals HIV infection and AIDS →
- Prevention of mother-to-child HIV transmission HIV infection and AIDS →
Adverse effects
Common
- Nausea, headache, malaise
- Macrocytosis
- Changes in skin and nail pigmentation
Contraindications
- Previous severe hypersensitivity (anaphylaxis, Stevens-Johnson) to zidovudine
Key interactions
- Ganciclovir, interferon alfa and other myelosuppressive or cytotoxic drugs
- Additive bone marrow toxicity
- Ribavirin
- Worsens anaemia in HIV-hepatitis C co-infection; the combination is not advised
- Stavudine
- Antagonism between these two thymidine analogues has been shown: the combination is avoided
What is monitored
- Complete blood count (haemoglobin and neutrophils) regularly
- Muscle symptoms and CK if myopathy is suspected
- Lactate if acidosis symptoms appear
- Viral load and CD4
Administration and safety
- Available as capsules, syrup and intravenous injection (the latter mainly during labour)
- In newborns, the liquid form needs careful checking of the ordered volume
- Do not confuse zidovudine with similar-sounding drugs; check the abbreviation AZT on orders
Nursing care
- Check blood count before and during treatment
- Watch for pallor, fatigue, fever or infections (anaemia, neutropenia)
- Ask about muscle pain or weakness
- In exposed newborns, coordinate prophylaxis as the team orders
Pregnancy and breastfeeding
It is approved to prevent mother-to-child HIV transmission and is now part of regimens for exposed newborns.
Test yourself
Think of the answer, then tap the question to see it.
What is zidovudine's most typical toxicity?
Bone marrow suppression: anaemia (often macrocytic) and neutropenia.
Why is zidovudine not combined with ganciclovir without close monitoring?
Both are myelotoxic and their marrow effects add up.
Which use of zidovudine is still relevant today?
Preventing mother-to-child HIV transmission, mainly in newborn prophylaxis.
Related drugs
Related conditions
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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 - ZIDOVUDINE capsule (DailyMed (U.S. National Library of Medicine), 2025); Zidovudine: 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.