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.



  • for the treatment of neonatal herpes simplex infections, varicella-zoster infections and herpes simplex encephalitis


  • acyclovir is an acyclic nucleoside with selective activity against herpes simplex and varicella-zoster virus
  • inhibits DNA synthesis and viral replication by competing with deoxyguanosine triphosphate for viral DNA polymerase
  • widely distributed in body fluids and tissues, including the brain and CSF
  • most of an administered dose is excreted unchanged in the urine; therefore, in neonates, the gestational age and post-natal age are important in determining how quickly acyclovir is eliminated from the body

Side Effects

  • local effects: erythema, inflammation, pain and phlebitis at site of infection
  • elevated serum creatinine (may result from precipitation of drug in collecting duct); incidence can be minimized by ensuring adequate hydration and infusing the drug over 1 hour
  • occasional rash or urticaria
  • monitor absolute neutrophil count at least twice weekly


  • 20 mg/kg IV q8h
  • for newborns < 34 weeks gestation extend interval to q12h
  • extend interval with impaired renal function
  • incompatible with TPN and lipid
  • maintain adequate hydration before, during and after the infusion


  • 5 mg/mL syringe prepared by the Department of Pharmacy; this is stable for 24 hours at room temperature
  • 50 mg/mL vial (10mL size); this is to be further diluted to a final concentration of 5 mg/mL

Sample Calculation

  • order reads: Acyclovir 20 mg IV q8h

    Step 1:

    Inject 1mL of 50 mg/mL solution and 9 mL SWFI (or D5W or NaC1 0.9%) into a 20 mL syringe; concentration is

    50 mg/10 mL = 5 mg/mL

    Step 2:Volume Required=Desired Dose
    Available Dose
    x    Available Volume
      =20 mg X 1 mL
     5 mg
      =4 mL 
NOTE:A concentration of 7 mg/mL may be used in infants who are fluid restricted (a concentration of up to 10 mg/mL has been used. However, the risk of pain and phlebitis may be increased)


  1. McEvoy G K (ed): AHFS Drug Information, American Society of Hospital Pharmacists, 1991.
  2. Roberts, RJ: Drug Therapy in Infants, W.B. Saunders, Toronto, 1984.
  3. Krogh CME et al (ed): Compendium of Pharmaceuticals and Specialties, Canadian Pharmaceutical Association, 1992.
  4. Taketomo CK, Hodding JH and Kraus DM: Pediatric Dosage Handbook, Lexi-Comp Inc., Cleveland, 1992.
  5. Young TE and Mangum OB: Neofax - A Manual of Drugs Used in Neonatal Care, Columbus, Ohio: Ross Laboratories, 1992.
  6. NEOFAX 2002
  7. Taketomo CK, Hodding JH and Kraus DM. Pediatric Dosing Handbook, 9th Edition 2002-2003, Lexi-Comp, Inc
  8. Kimberlin DW et al. Safety and efficacy of high-dose intravenous acyclovir in the management of neonatal Herpes simplex virus infections, Pediatrics 2001;108:230-238.


November 2002

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