Disclaimer to the On-line Edition
This Manual has been designed for use in the NICU at London Health Sciences Centre (LHSC), London, Ontario, Canada, and represents clinical practice at this institution. The information contained within the Manual may not be applicable to other centres. If users of this Manual are not familiar with a drug, it is recommended that the official monograph be consulted before it is prescribed and administered. Any user of this information is advised that the contributors, Editor and LHSC are not responsible for any errors or omissions, and / or any consequences arising from the use of the information in this Manual.



  • Antiviral agent used in the treatment of herpes simplex and varicella-zoster infections

Dosage Guidelines

Acute Herpes simplex infections:

Post Menstrual Age (PMA)


Less than or equal to 32 weeks

20 mg/kg/dose IV q12 hours

Greater than 32 weeks

20 mg/kg/dose IV q8 hours

Treat for 21 days for disseminated or CNS infections and 14 days for isolated skin, eye and mouth disease.

Anti-viral suppressive therapy (to start after initial treatment of neonatal herpes simplex disease with CNS involvement):  Use Cerner Dose Calculator to calculate mg/m2 dose

300 mg/m2/dose oral q8 hours for 6 months

Varicella zoster treatment:

10–15 mg/kg/dose IV q8 hours x 5 to 10 days; continue for at least 48 hours after appearance of last new lesion


  • IV intermittent slow infusion over 60 minutes
  • Maintain adequate hydration before, during and after infusion
  • To make 20 mL of a 5 mg/mL solution:

1. Draw up 2 mL from the 50 mg/mL vial

2. Add to 18 mL D5W to make a total volume of 20 mL

  • Do not refrigerate

Adverse Effects

  • Phlebitis, transient elevations in serum creatinine and liver function tests, crystal nephropathy with acute tubular necrosis, neutropenia


Monitor liver enzymes, urea, creatinine weekly

Monitor CBC including absolute neutrophil count twice weekly

Contact pharmacist for dosing adjustments in renal impairment


Supplied As

50 mg/mL vial (must be further diluted to a final concentration of 5 mg/mL)

5 mg/mL patient specific syringe, prepared by Pharmacy


Updated: March 2021