Drug Class: Antiviral

Table of Contents

Valtrex (Valacyclovir)


Valtrex (Valacyclovir) is an antiviral medication used to treat infections caused by certain viruses. It helps the body fight infection by slowing the growth and spread of the herpes virus. It is used to treat shingles (caused by herpes zoster), genital herpes, and cold sores around the mouth.

Valtrex is also a treatment for cold sores in children over the age of 12 years old and as a chickenpox medication in children who are over the age of 2 years.

This information is for educational purposes only. Not every known side effect, adverse effect, or drug interaction is in this database. If you have questions about your medicines, talk to your health care provider.

How to Take It

Valacyclovir comes as a tablet to take by mouth. It is usually taken every 8 hours (three times a day) for 7 days to treat shingles. To treat genital herpes it is usually taken twice a day for 5 days. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take valacyclovir exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor. Use this medication as soon as possible after symptoms appear.

Side Effects

Side effects that may occur while taking this medicine include:

  • stomach pain
  • joint pain
  • headache
  • constipation
  • vomiting
  • cold symptoms, e.g., nasal congestion / runny nose / sneezing
  • nausea
  • loss of voice
  • muscle aches
  • dizziness

Contact your doctor immediately if you experience:

  • confusion
  • shortness of breath
  • itching
  • mouth sores
  • skin rash
  • yellowness of the skin or eyes
  • blood in urine
  • hallucinations
  • hyperventilation
  • bleeding or bruising easily
  • irritability
  • chills
  • fast or irregular heartbeat
  • bleeding gums
  • difficulty speaking
  • loss of consciousness
  • fever

Warnings & Precautions

  • Get immediate medical attention if you experience breathing difficulty, itching, rash, or swelling, or severe dizziness.
  • If you are allergic to acyclovir (Zovirax), valacyclovir, or any other drugs, let your doctor know immediately.
  • Inform your doctor of what medications you are currently taking, especially probenecid (Benemid) or cimetidine (Tagamet). This also includes prescription, non-prescription, and vitamins.
  • If you experience side effects such as: unsteady movements, mood or mental changes, difficulty speaking, or any changes in urine output, contact your doctor immediately.
  • Inform your doctor if you have or have ever had kidney or liver disease, problems with your immune system, human immunodeficiency virus infection (HIV), or acquired immunodeficiency syndrome (AIDS).
  • Do not give this medication to a child without first consulting your doctor.
  • For an overdose, seek medical attention immediately. For non emergencies, contact your local or regional poison control center at 1-800-222-1222.

Drug Interactions

Before taking any new medicine, either prescription or over-the-counter, check with your doctor or pharmacist. This includes supplements and herbal products.

Dosage & Missed Dose

Valtrex should be taken exactly as prescribed by your doctor, usually in evenly spaced intervals. It is available in oral tablet form, in 500 mg and 1 gram. For the best results, take it at the very first sign of an outbreak.

As soon as a rash appears for chickenpox or shingles, take this medication immediately. If you feel tingling, itching or burning (e.g., cold sores or genital herpes) take this medication as soon as possible.

Take your next dose as soon as you remember. If it is time for your next dose, skip the missed dose and go back to your regular schedule. Do not double doses or take extra medicine to make up for the missed dose.


Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (preferably not in the bathroom). Throw away any medication that is outdated or no longer needed.


Valtrex should be used only when clearly needed during pregnancy. Talk to your doctor about the risks and benefits.

It can pass into breast milk, but is unlikely to harm a nursing infant. Before breast-feeding, talk with your doctor.

More Information

For more information, talk to your doctor, pharmacist or health care provider, or you can visit this website, https://www.nlm.nih.gov/medlineplus/druginfo/meds/a695010.html for additional information from the manufacturer of this drug.