Dose and Administration

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
≤29	>28	12
30 to 36	0 to 14	24
30 to 36	>14	12
≥37	All	8

Treat disseminated Neonatal herpes simplex virus (HSV) for 21 days if baby has CNS involvement^1,2
Treat Varicella zoster virus (VZV) for 7 – 10 days¹
Increase dose interval if significant renal impairment.
Reduce dose if severe renal failure (serum creatinine greater than 130 umol/L)^1,3

Indications

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

Contraindications

Hypersensitivity to aciclovir.
Caution in preterm infants, especially extreme immaturity.
Caution in infants with renal, hepatic or electrolyte abnormalities or significant hypoxia¹.
Caution in infants with underlying neurological abnormalities¹.

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 aciclovir 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 aciclovir 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

Significant adverse effects are uncommon but include: neutropenia, renal failure, non herpetic skin eruptions, thrombotic thrombocytopenic purpura (TTP)/haemolytic uremic syndrome (HUS).
Increase in bilirubin, urea and creatinine.
Venous irritation, soft tissue injury at site of IV injection.
Reversible neurological reactions.

Special Considerations

Check renal function prior to commencing and during therapy. In renal failure, double the dose interval and decrease the dose. In severe renal failure use 5 mg/kg/dose^1,3.
Risk of transient renal dysfunction and crystalluria is minimised by slow infusion rates and adequate patient hydration.
Resistant viral strains may emerge during long term therapy. There is NO evidence Aciclovir will stop transmission of the virus
Do not administer by bolus IV injection IM or SC.