Zovirax Treatment for Cold Sores

Antiviral meds that also help with shingles and chickenpox

Zovirax (acyclovir) is a prescription medication drug that is used to treat cold sores, shingles, chickenpox, and sometimes genital herpes. These infections are caused by the herpes simplex and herpes zoster viruses, and though the drug does not cure the infections, Zovirax can decrease the severity and length of the outbreaks.

Woman applying cold sore cream on her lips
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Antiviral Medications on the Market

Zovirax is the oldest of the antiviral medications out there, as it has been available since 1982 in the topical form as an ointment cream, and since 1985 as a pill. The cream formulation for topical administration should be applied five times per day for four days. Now Zovirax is available in a generic form and is the only antiviral available as intravenous medication.

There are two other FDA approved drugs on the market that treat the herpes virus: Valtrex (valacyclovir) and Famvir (famciclovir).

Valtrex, manufactured by GlaxoSmithKline, was approved by the FDA in 1995 and was the second antiviral medication to come to market in the USA. Valtrex comes in pill form and is a prodrug of acyclovir (meaning that the body converts it to acyclovir after it has been absorbed). Valtrex delivers acyclovir more efficiently, allowing the body to absorb much of the drug. This has the added advantage of needing less administration throughout the day.

Famvir is manufactured by Novartis and is also a well-absorbed drug. The body converts Famvir into the long-acting antiviral drug penciclovir that can be taken less frequently than Zovirax.

How Zovirax Treats Cold Sores

Cold sores, also known as herpes labialis or fever blisters, are highly infectious sores on the lip and outer edge of the mouth.

Cold sore outbreaks heal faster when Zovirax is taken, compared to letting the virus run its course. New sores are also kept from forming and associated pain and itching of cold sores are also decreased. Zovirax may also help reduce how long the pain remains after the sores have healed.

For those with a weakened immune system and more frequent outbreaks, Zovirax can reduce the number of future episodes.

Why Cold Sores Keep Coming Back

Zovirax is an antiviral drug but it is not a cure for the herpes virus. The viruses that cause these infections continue to live in the body even when symptoms and outbreaks are not visible.

Antiviral medications work best when started at the first sign of an outbreak, as directed by your healthcare provider. It may not work as well if you delay treatment.

Treatment should be started as early as possible following the first onset of signs and symptoms (such as tingling or itch, or when lesions first appear).

Keeping the amount of antiviral drugs in your body at a constant level is crucial in fighting the virus. For this reason, be sure to take your medication at evenly spaced intervals, at the same times each day. Continue taking the full prescribed amount of your medication, even if your symptoms go away after a few days. Do not change your dose or skip any doses, follow the advice of your healthcare provider.

Be sure to tell your healthcare provider if your condition persists or worsens even after you have finished your prescribed medication dosage.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. U.S. Food and Drug Administration (FDA). Highlights of prescribing information: Zovirax (acyclovir) cream.

  2. DailyMed. Label: Valtrex-valacyclovir hydrochloride tablet, film coated.

  3. Food and Drug Administration. Highlights of prescribing information: Famvir (famciclovir).

  4. Cleveland Clinic. Cold sores: treatment and management.

  5. Glenny AM, Fernandez mauleffinch LM, Pavitt S, Walsh T. Interventions for the prevention and treatment of herpes simplex virus in patients being treated for cancer. Cochrane Database Syst Rev. 2009;(1):CD006706. doi:10.1002/14651858.CD006706.pub2

By Heather L. Brannon, MD
Heather L. Brannon, MD, is a family practice physician in Mauldin, South Carolina. She has been in practice for over 20 years.