Acyclovir for Chickenpox

Chickenpox is an infectious highly contagious illness caused by the varicella-zoster virus, a member of the herpesvirus family. The classic sign of chickenpox is a rash that turns into itchy, fluid-filled blisters. The blisters are often intensely itchy. The rash usually first shows up on the face, chest, and back then spreads to the rest of the body.

Acyclovir can be used to treat chickenpox. It accelerates the healing, limits the number of lesions, and reduces the duration and magnitude of fever. It should be used within the first 24 hours after the onset of the chickenpox rash.

Acyclovir dosage for chickenpox

  • Children >= 2 years and <= 40 kg (immunocompetent): 20 mg/kg (up to 800 mg) 4 times daily for 5 days.
  • Adults and Children >40 kg (immunocompetent): 800 mg 4 times a day for 5 days.

When Acyclovir is appropriate?

Acyclovir is recommended for people who are likely to develop a severe varicella or its complications, including5:

  • Persons older than 12 years of age
  • Persons with chronic skin (e.g eczema, atopic dermatitis) or lung disease (e.g. cystic fibrosis)
  • Persons receiving corticosteroids or long-term salicylates
  • Persons with weakened immune system

The American Academy of Pediatrics (AAP) does NOT recommend that otherwise healthy children younger 12 years of age receive oral acyclovir for chickenpox.

In healthy persons virus replication stops at about 72 hours after onset of rash, and there is only a small period of time when an antiviral treatment would be useful.

Chickenpox tends to be more severe in adults than children, and adults have a higher risk of developing complications. Acyclovir therapy in adults can reduce the time to full crusting of lesions from 7.4 days to 5.6 days, reduce the number of lesions by 46%, and shorten the duration of fever2.

Disadvantages of Acyclovir use in chickenpox

Studies of antibody titres after acyclovir in childhood chickenpox indicate that the humoral immunological response is affected at 28 days and one year3, but it is unclear whether the immune response is altered.

See also


  • 1. Balfour HH Jr, Edelman CK, Anderson RS, Reed NV, Slivken RM, Marmor LH, Dix L, Aeppli D, Talarico CL. Controlled trial of acyclovir for chickenpox evaluating time of initiation and duration of therapy and viral resistance. Pediatr Infect Dis J. 2001 Oct;20(10):919-26. PubMed
  • 2. Wallace MR, Bowler WA, Murray NB, Brodine SK, Oldfield EC. Treatment of adult varicella with oral acyclovir. A randomized, placebo-controlled trial. Ann Intern Med. 1992 Sep 1;117(5):358-63.
  • 3. Englund JA, Arvin AM, Balfour HH Jr. Acyclovir treatment for varicella does not lower gpI and IE-62 (p170) antibody responses to varicella-zoster virus in normal children. J Clin Microbiol. 1990 Oct;28(10):2327-30.
  • 4. Chickenpox Treatment & Management MedScape
  • 5. Managing People at Risk for Severe Varicella CDC

Author: OriginalDrugs Team
Last reviewed: May, 2015

Quick facts


  • Because chickenpox tends to be mild in healthy children, most physicians do not feel that taking acyclovir is necessary.
  • The chickenpox vaccine provides 70-90% rate of protection against infection in vaccinated persons.