OverviewDosageSide EffectsInteractionsHalf-Life

Generic Name: Valacyclovir, valaciclovir, valacyclovir hydrochloride

Brands: Valtrex

Class: Antiviral

Availability: Prescription required

Molecular Formula: C13H20N6O4

Substance UNII: 8S9ACT5D06

What is Valacyclovir?

Valacyclovir is an antiviral. It is often sold under the brand names Valtrex.

What is Valacyclovir Used For?

Valacyclovir is for the treatment of outbreaks of herpes simplex or herpes zoster viruses. In some cases, clinicians may prescribe it to prevent cytomegalovirus (CMV) infection after a kidney transplant, which is an infection in the Herpesviridae family

How Does Valacyclovir Work?

The body converts valacyclovir to acyclovir, a potent inhibitor of viral DNA replication. Specifically, it inactivates the viral DNA polymerase, an enzyme (specialized protein) necessary for DNA replication. Put simply, the drug can prevent the virus from reproducing. 

How Long Does it Take for Valacyclovir to Work?

That will depend on the severity of the symptoms. Most people will see some relief in as little as 48 hours. It may take longer for the signs (sores and blisters) of the outbreak to disappear completely, though, perhaps up to 10 days. 

Do Not Use Valacyclovir If:

There are several situations where this medication may not be the right choice for you. According to the FDA, the following should not use valacyclovir:

  • There is a history of sensitivity to Valtrex, valacyclovir, acyclovir, or any ingredients in the formula. 

Please note that this list may not be complete, and there may be other situations where valacyclovir use is not advisable.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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