ACYCLOVIR

Zovirax IV

 Reviewed by Dorothy Cooper and Dr Carl Kuschel
September 1999
Administration Newborn Drug Protocol Index Newborn Services Home Page

 

Dose and Administration
  1. 20 mg/kg/dose IV infusion by syringe pump over one hour.
Postmenstrual Age
(weeks)		 Postnatal Age
(days)		 Dosing Interval
(hr)
≤29 0 to 28 24
>28 12
30 to 36 0 to 14 24
>14 12
≥37 All 8

Indications

  1. Neonatal herpes simplex infections (especially if CNS and pulmonary involvement).
  2. Neonatal varicella zoster infections.

Contraindications

  1. Hypersensitivity to acyclovir.
  2. Caution in preterm infants, especially extreme immaturity.
  3. Caution in infants with renal dysfunction or renal failure.

Clinical Pharmacology

Antiviral agent which is highly active in vitro against herpes simplex (types 1 and 2) and varicella zoster viruses. Preferentially taken up by infected cells and then phosphorylated to the active compound acyclovir triphosphate. Acts as an inhibitor of, and substrate for, the herpes specified DNA polymerase. Prevents further viral DNA synthesis without affecting normal cellular processes. Toxicity to mammalian host cells is low.

Oral absorption of acyclovir is limited (bioavailability 15-30%) and may involve a saturable process, but does not appear to be altered by food. Widely distributed throughout the body fluids and tissues. CSF concentrations approximately 50% that of plasma. Low binding (9-24%) to human plasma protein. Eliminated, mainly unchanged via the kidney, primarily by glomerular filtration. Elevated serum concentrations may be reduced by haemodialysis.

Possible Adverse Effects

  1. Very few adverse effects have been reported in clinical studies.
  2. Venous irritation, soft tissue injury at site of IV injection.
  3. Gastrointestinal disturbances (nausea, vomiting).
  4. Reversible neurological reactions are rare.
  5. Transient renal dysfunction and crystalluria.

Special Considerations

  1. Check renal function prior to commencing therapy. Modify dosing regime if serum creatinine elevated.
  2. Risk of transient renal dysfunction and crystalluria is minimised by slow infusion rates and adequate patient hydration.
  3. Monitor renal function during course of therapy.
  4. Resistant viral strains may emerge during long term therapy.
  5. Not compatible with dopamine, dobutamine and morphine.
  6. There is NO evidence acyclovir will stop transmission of the virus.
  7. Acyclovir is compatible with breastfeeding.
  8. Do not administer by bolus IV injection IM or SC.
  9. Sodium content 4.2mEq/g.