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Valacyclovir is a prescription drug available in oral tablet form. It is the generic version of the brand-name drug Valtrex. Doctors prescribe valacyclovir to treat infections caused by the herpes virus, including genital herpes.

Below, we take a closer look at this drug and outline how it differs from acyclovir. We also look at the drug’s side effects and warnings.

There are two types of the herpes simplex virus: HSV-1 and HSV-2.

HSV-1 is the cause of most cold sores, while HSV-2 is involved in most cases of genital herpes. However, both HSV-1 and HSV-2 can cause herpes infections in either location.

A person can contract an HSV-1 infection through oral-to-oral contact such as kissing. It is also possible to pass on the HSV-1 virus through oral-to-genital contact, which results in genital herpes. People are more contagious when they have a flare-up of the virus and have active sores.

People usually get the HSV-2 virus through sexual contact and can pass on an HSV-2 infection even if they do not have obvious symptoms. Condoms can reduce the risk of passing on genital herpes, but this is not guaranteed.

Another form of herpes virus is called the herpes zoster virus, which is more commonly known as shingles. The varicella-zoster virus (VZV), which is also known as chickenpox, lays dormant in the body after the initial infection. In some people, the virus may reactivate as shingles.

A person can only become infected with shingles if they have previously had chickenpox. However, someone who has never had chickenpox can become infected with the virus through someone with shingles if they have direct contact with open sores.

Learn more about shingles and how it is spread here.

Valacyclovir is only available by prescription. It treats the following viral infections:

  • oral herpes or cold sores
  • genital herpes
  • varicella-zoster virus (VZV) or chickenpox
  • herpes zoster or shingles

This antiviral drug can also help reduce the risk of transmitting genital herpes to another person.

There is an ongoing study to look into valacyclovir’s potential use for treating mild Alzheimer’s disease in people with HSV-1 or HSV-2.

Possible mild side effects of taking valacyclovir include:

  • headache
  • nausea and vomiting
  • upset stomach
  • dizziness

Uncommon side effects include:

  • painful menstruation
  • depression
  • joint pain
  • low blood cell counts

In some cases, individuals may experience severe side effects such as kidney failure and nervous system problems.

There are some warnings that come with valacyclovir.

  • People with advanced human immunodeficiency virus (HIV) and those who have recently received a bone marrow or kidney transplant may be at risk for blood disorders such as thrombotic thrombocytopenic purpura (TTP) or hemolytic uremic syndrome (HUS).
  • Some people may experience central nervous system side effects, such as confusion and hallucinations. This side effect is more likely in older adults.
  • Valacyclovir may cause an allergic reaction in some people. If a person has an allergic reaction to valacyclovir, they should seek emergency medical care.
  • Valacyclovir can interact with certain medications. People should talk to their doctor about potential interactions with any drugs, herbs, vitamins, or supplements they are taking.

Both valacyclovir and acyclovir treat viral herpes infections and both are equally effective. The table below shows some key differences.

Typically taken between one and three times per day, depending on the infection typeSometimes taken up to five times per day, depending on the infection type
Can have a higher costOften lower in cost
Oral tablet onlyOral capsule, tablet, suspension, or topical ointment or cream

Both of these generic medications are covered by most medical insurance plans. However, a person should check with their plan provider to confirm coverage.

A person can only purchase valacyclovir with a prescription from a doctor, but there are many online pharmacies that offer fast and efficient ways to receive medications.

When ordering online, websites such as Roman require that a person do one of the following:

  • Already have a prescription to upload.
  • Complete a questionnaire on symptoms and provide visual identification for a medical professional to review.
  • Provide the contact details for their doctor, so the company can contact them to verify the prescription.

Some companies may have other rules that individuals must follow to receive their prescribed medication.

Some companies, such as Lemonaid, offer valacyclovir in a way that the U.S. Food and Drug Administration (FDA) has not approved, meaning that the way the company prescribes the medication is not how the label recommends. This is known as off-label use. A person should consider contacting their doctor before using medications in this way.

The most common difference between brand-name and generic drugs is the cost. Generic versions of drugs may also look different from their brand-name counterparts. Generic medicines have the same active ingredients as brand-name drugs and both types are FDA approved.

Once an initial patent for a drug expires, companies can begin selling generic forms. Because repeat clinical testing is not necessary for generic medications, they cost less.

The brand name for valacyclovir is Valtrex. Acyclovir, a similar antiviral, goes by the brand name Zovirax.

Valacyclovir is an effective antiviral treatment for chickenpox, shingles, oral herpes, and genital herpes. While the drug cannot cure genital herpes, it can help a person manage their symptoms. It can also reduce instances of transmission.

If a person suspects they have a viral herpes infection, they should see a doctor. With shingles, treatment is necessary to get rid of the infection and prevent complications.