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Drug dosage identifier

Zidovudine

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Dose and administration

Dose for the first 4 weeks following delivery

Oral

Gestation Dose
Term 4mg/kg/dose every 12 hours, or
2mg/kg/dose every 6 hours.
Adherence is better with 12-hourly dosing.
Preterm 30-36 weeks  2mg/kg/dose every 12 hours for 2 weeks, then 2mg/kg/dose every 8 hours.
Preterm <30 weeks 2mg/kg/dose ever 12 hours for 4 weeks, then 2mg/kg/dose every 8 hours.

Intravenous

Gestation Dose
Term 1.5mg/kg/dose every 6 hours.
Preterm   1.5mg/kg/dose every 12 hours.

Over 1 Month to 3 months

Route Dose
Oral 4mg/kg/dose every 12 hours.
IV 1.5mg/kg/dose every 6 hours.

Indications

  • 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.

Contraindications

  • Jaundice requiring phototherapy (relative contraindication)
  • Neutrophil count <0.75 x 109/L
  • Haemoglobin <80g/L
  • Platelet count <50 x 109 /L

Precautions

Renal impairment - consider reducing dose according to clinical response.3

Clinical pharmacology

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.

  1. Anaemia, leucopenia (mainly neutropenia). Less common: thrombocytopenia, pancytopenia.
  2. Vomiting, diarrhoea, abdominal pain.
  3. Increase in liver function tests and bilirubin.
  4. Rash.
  5. Myopathy.
  6. Lactic acidosis, with or without hepatic failure.
  7. Persistent mitochondrial dysfunction.
  8. Cardiomyopathy (rare).
  9. Discolouration of nails & skin.
  10. Possible increased risk of sepsis.

Special considerations

Monitor

  • Full blood count, platelets, bilirubin, liver function, and renal function.
  • 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 Authority" application.
  • 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 Hospital).

Management of Zidovudine administration

Description

Oral solution (Retrovir 10mg/ml):  Clear, pale yellow, strawberry-flavoured, sugar-free solution.
IV Preparation (Retrovir 10 mg/ml):  Clear, almost colourless solution. pH 5.5

Prescription

Maintenance doses are charted on prescription chart in mg/dose.

Administration

Intravenous infusion 3,6

  1. Must be diluted to 2 mg/ml with glucose 5%.
  2. Compatible diluents: glucose 5 % and sodium chloride 0.9%.
  3. Administer dose over one hour.
  4. Flush well between different infusions, fluids, or medications.
  5. Compatible at Y-site junction with the following drugs when they are diluted according to NICU protocols: acyclovir, amikacin, fluconazole, gentamicin, heparin.
  6. Incompatible with meropenem when it is diluted according to NICU protocol.

Oral

Can be given with food. Best given between 2 feeds to optimise absorption.

Observation and documentation

  1. Assess for signs of adverse effects.
  2. Assess IV site for signs of extravasation.
  3. Record urine output.

Storage

  • Store unopened Retrovir® injection vials below 30°C and protect from light.
  • Store Retrovir® Oral Liquid below 30°C.

Selected references

  1. Capparelli EV, Mirochnick M, Dankner WM, et al. Pharmacokinetics and tolerance of zidovudine in preterm infants. J Pediatr 2003; 142:47-52.
  2. Other related links:
    Starship Newborn Services - Guidelines for Paediatric Management of HIV Positive Pregnant Women
    www.aidsinfo.nih.gov - Guidelines for the use of antiretroviral agents in paediatric HIV infection
  3. Paediatric Formulary (7th ed.) 2005. London: Guy's and St. Thomas', King's College and University Lewisham Hospitals.
  4. Sweetman SC (Ed.). Martindale: The Complete Drug Reference (34th ed.). London: Pharmaceutical Press, 2005
  5. Retrovir TM Oral Formulations (Data sheet) and IV for Infusion (Data sheet). Auckland: GlaxoSmithKline NZ Ltd, 2005.
  6. Trissel LA (ed.). Handbook on Injectable Drugs (13th ed.). Bethesda: American Society of Health-Systems Pharmacists, Inc., 2005.

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Document Control

  • Date last published: 30 November 2010
  • Document type: Drug Dosage Guideline
  • Services responsible: ADHB Pharmacy, Neonatology, Paediatric Infectious Diseases
  • Editor: Sarah Bellhouse
  • Review frequency: 2 years