Retrovir, AZT (Azidothymidine)
Reviewed by Dr Simon Rowley, Dr Lesley Voss (Paediatric ID), Brenda Hughes, and Dana Lui
November 2010 -Change to dosing schedule
See also the
HIV and pregnant women
Dose and Administration 1,2
Dose for the first 4 weeks following delivery
4mg/kg/dose every 12 hours, or
2mg/kg/dose every 6 hours.
- Adherence is better with
Preterm 30-36 weeks
2mg/kg/dose every 12 hours for 2 weeks, then 2mg/kg/dose every 8
Preterm <30 weeks
2mg/kg/dose ever 12 hours for 4 weeks, then 2mg/kg/dose every 8
1.5mg/kg/dose every 6 hours.
1.5mg/kg/dose every 12 hours.
Over 1 Month to 3 months
4mg/kg/dose every 12 hours.
1.5mg/kg/dose every 6 hours.
- Maternal HIV status positive – as part of the antepartum, intrapartum
and 4 weeks newborn regimen of anti retroviral treatment to reduce perinatal
transmission of HIV virus.
- May also be used in conjunction with other drugs as part of treatment in
infants identified as being HIV-infected during the first few weeks of life.
- Jaundice requiring phototherapy (relative contraindication)
- Neutrophil count <0.75 x 109/L
- Haemoglobin <80g/L
- Platelet count <50 x 109 /L
- Renal impairment - consider reducing dose according to clinical
Clinical Pharmacology 1,4
Zidovudine is a pyrimidine nucleoside analogue and a potent inhibitor of HIV
virus with varying efficacy against other retroviruses. It is
phosphorylated by the host cell to the active triphosphate. It acts then as a
reverse transcriptase inhibitor (inhibits viral RNA dependent DNA polymerase).
Zidovudine is rapidly absorbed from the GIT with bioavailability of 60- 70 % and
peak plasma levels at one hour post dose. Absorption is delayed by food, but
bioavailability is probably unaffected.
Zidovudine is eliminated primarily through glucuronidation by uridine
diphosphate glucuronyl transferases (UGTs) to an inactive metabolite, and to a
lesser extent through renal excretion of unchanged drug. In term infants
UGT activity is depressed at birth but quickly increases during the first few
weeks of life, quadrupling Zidovudine clearance in the first month of life.
In preterm infants, clearance is approximately 35% of that of term infants.
Postnatal age is the best predictor of Zidovudine clearance with other factors
being gestational at birth, and serum creatinine.
Possible Adverse Effects
Adverse effects tend to be dose-related and reversible. With more advanced
disease the toxicity is greater.
- Anaemia, leucopenia (mainly neutropenia). Less common: thrombocytopenia,
- Vomiting, diarrhoea, abdominal pain.
- Increase in liver function tests and bilirubin.
- Lactic acidosis, with or without hepatic failure.
- Persistent mitochondrial dysfunction.
- Cardiomyopathy (rare).
- Discolouration of nails & skin.
- Possible increased risk of sepsis.
Special Considerations 1,3,4,5
- Full blood count, platelets, bilirubin, liver function, and renal
- Hepatic function: If there is hepatic impairment, consider
dose reduction, especially if adverse effects suggest toxicity.
- Renal function. For renal impairment, use doses at the lower end of
the dose range and adjust according to clinical response.
- Zidovudine for babies being discharged
- Currently zidovudine oral liquid is available with a “Special
- Availability: Pharmac
- Special Authority forms: ADHB Intranet/Medicines Information/Special
Authority Forms or Pharmac
- The Ministry of Health can be contacted for approval via freephone
0800 243 666
If the Special Authority is granted, the medicine can be obtained from
most community pharmacies (e.g. Level 5 Pharmacy, Auckland City