Antiviral Medicines for Chickenpox

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Antiviral Medicines for Chickenpox


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Antiviral medicines can be taken by mouth (orally), given by injection into a vein (intravenous, or IV), or applied on the skin (topically). Acyclovir is the antiviral medicine used most often to treat chickenpox (varicella). But other antivirals may be used.

Antiviral eye ointments are also available. They can be used on your eyes to treat chickenpox blisters.

How It Works

Antiviral medicines stop the growth of the chickenpox (varicella-zoster) virus.

Why It Is Used

Antiviral medicines may be prescribed if a person has been exposed to chickenpox and can't get the chickenpox vaccine or antibodies to help prevent chickenpox.

These medicines may also be used to help treat chickenpox.

Antiviral medicines are generally given to people who are more likely to become seriously ill or develop complications from chickenpox, such as:

  • People who have a long-term illness, such as skin or lung disease.
  • People with impaired immune systems.
  • Pregnant women with serious complications of chickenpox.
  • Babies born early or babies who have a low birth weight and whose mother had chickenpox.

These medicines are usually NOT recommended for:

  • Healthy children or adults as a way to prevent them from having chickenpox if they have been exposed to the illness.
  • Healthy children as a way to treat chickenpox.

Antiviral medicines can help protect family members of a person with chickenpox from getting chickenpox. But they aren't used regularly if a person's symptoms are not severe or the illness is not causing problems for the family.

How Well It Works

Antiviral medicines may shorten the length of illness from chickenpox, cause fewer blisters to form, and help blisters heal faster. They work best if taken right after the first signs of chickenpox rash appear.

It is not known whether antiviral medicines reduce the chance of developing complications of chickenpox. Antiviral medicines may reduce the complications of chickenpox, such as varicella pneumonia, in people with impaired immune systems.

Side Effects

Antiviral medicines have few side effects. They include:

  • Headache or feelings of general illness (malaise).
  • Nausea and vomiting.
  • Diarrhea or constipation. This is rare.
  • Kidney problems in people who receive large doses of acyclovir by rapid injection into a vein. This is rare.

The effect of antiviral medicines on pregnant women and their fetuses is not known.

The effect of antiviral medicines on immunity to chickenpox is not known.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Consider the following when deciding whether to treat a family member with antiviral medicines:

  • Antiviral medicines are expensive. But at least some of the cost of medicine is usually covered under provincial health plans or private health insurance plans.
  • Treatment with antiviral medicines may reduce the length of time you can pass the chickenpox virus to other people.
  • It is not clear whether antiviral medicines reduce lost time from work, school, or day care.
  • People who take these medicines need to drink extra liquids to prevent kidney problems. People who have kidney problems need to take a lower dose.

Acyclovir (Zovirax) is the most prescribed antiviral medicine. It has fewer side effects than the other antiviral medicines. But it does not reduce itching, nor does it stop the spread of the chickenpox virus from one person to another.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.


By Healthwise Staff
Primary Medical Reviewer Susan C. Kim, MD - Pediatrics
Specialist Medical Reviewer Thomas Emmett Francoeur, MD, MDCM, CSPQ, FRCPC - Pediatrics
Last Revised May 26, 2010

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