Treating Cold Sores With Valtrex and Other Prescription Drugs

Antiviral drugs can cut the time that cold sores last.

A cold sore on the lips.
A cold sore on the lips. Todd Keith/Getty Images

Several medications, including Valtrex, are available to treat cold sores. Some are used topically (on the skin) and others are orally (by mouth), but the goal is to treat cold sores as early as possible.

That's because starting a medication when prodromal symptoms such as burning, tingling or redness start will give a person with a cold sore the best chance of preventing an actual blister from forming or of shortening their course once blisters do appear.

Cold Sore Treatment and FDA Approval

A number of antiviral medications are used to treat herpes infections, which cause cold sores, also known as fever blisters.

While the FDA has approved the use of certain drugs for cold sores, some antiviral drugs aren't specifically FDA-approved for cold sores but have been shown in clinical studies to be effective treatments. Given this, receiving a prescription for an off-label use of one of these drugs may help eliminate or prevent cold sores.

The decision to use a medication that is prescribed off-label should be made based on current scientific data and discussed thoroughly with your health care provider.

Cold Sore Treatment Benefits

Antiviral drugs can have several effects on oral herpes simplex virus infections, including cold sores. These medications can decrease the time it takes for cold sores to heal and reduce symptoms, especially pain. And if taken soon enough, they can prevent lesions from occurring, reduce the number and size of lesions developed, as well as decrease the amount of viral shedding.

The First Cold Sore Outbreak

The first outbreak of any herpes simplex infection is usually worse than recurrent infections. An initial outbreak of oral herpes should be treated with oral medications, while recurrences can be treated with topical or oral medications.

The first episode (which generally occurs in childhood) is also treated longer, usually 7 to 10 days with an antiviral medication.

Recurrent infections, on the other hand, are treated for a shorter period of time.

Topical Denavir for Cold Sores

Denavir (Penciclovir 1 percent cream) is FDA-approved for recurrent cold sores. Starting treatment within one hour of an outbreak can reduce the time to healing by two days as well as reduce symptoms. Denavir can also decrease the duration of viral shedding.

Overall, the earlier Denavir is started the better the benefits. That being said, improvement is often still possible when treatment is started after vesicles (the cold sores) develop.

Why Acyclovir Helps Cold Sores

Zovirax (Acyclovir 5 percent cream) is also FDA-approved for the treatment of recurrent cold sores. In studies, frequent application of the cream reduced the time to healing by about 12 hours.

Oral acyclovir given five times a day for primary gingivostomatitis in children can substantially reduce the duration of fever, eating problems, and drinking difficulties as well as viral shedding. Using low dose oral acyclovir for cold sores can shorten the duration of symptoms, but higher doses may be needed to reduce pain.

The Effect of Famciclovir on Cold Sores

Famvir (Famciclovir) is approved by the FDA for the treatment of cold sores.

If started at the first sign of symptoms, taking a single high dose of Famvir can shorten the herpes infection by two days.

Valtrex Is a Well-Known Treatment for Cold Sores

Valtrex (Valacyclovir) is also approved by the FDA to treat cold sores. If started at the first sign of symptoms, taking Valtrex twice a day for one day can shorten the duration of herpes infection.

Suppressive Therapy for Cold Sores

Suppressive therapy, which means taking medication every day to prevent cold sore outbreaks, is not yet FDA-approved. That being said, studies have shown that people who have more than six recurrences or more per year can benefit from taking daily doses of acyclovir or Valtrex to reduce the number of recurrences and decrease viral shedding.


CDC. (2015). Sexually Transmitted Diseases Treatment Guidelines. 

Habif, Thomas. "Warts, Herpes Simplex, and Other Viral Infections" Clinical Dermatology, 4th Edition. Ed. Thomas Habif, MD. New York: Mosby, 2004. 381-388.

Usatine RP, Tinitigan R. Nongenital herpes simplex virus. Am Fam Physician. 2010 Nov 1;82(9):1075-82.

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