Skip to Content
Vaccines aren’t just for kids. Is your teen protected?

Generic Name: valacyclovir (val a SYE kloe veer)
Brand Name: Valtrex

What is valacyclovir?

Valacyclovir is an antiviral drug. It slows the growth and spread of the herpes virus to help the body fight the infection.

Valacyclovir is used to treat infections caused by herpes viruses, including genital herpes, cold sores, and shingles (herpes zoster) in adults.

Valacyclovir is used to treat cold sores in children who are at least 12 years old, or chickenpox in children who are at least 2 years old.

Valacyclovir will not cure herpes and will not prevent you from spreading the virus to other people. However, this medicine can lessen the symptoms of an infection.

Valacyclovir may also be used for purposes not listed in this medication guide.

What is the most important information I should know about valacyclovir?

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

What should I discuss with my healthcare provider before taking valacyclovir?

You should not use this medicine if you are allergic to valacyclovir or acyclovir (Zovirax).

To make sure valacyclovir is safe for you, tell your doctor if you have:

  • kidney disease (or if you are on dialysis);

  • HIV/AIDS, or other conditions that can weaken the immune system; or

  • a history of kidney transplant or bone marrow transplant.

It is not known whether this medicine will harm an unborn baby. However, herpes virus can be passed from an infected mother to her baby during childbirth. If you have genital herpes, it is very important to prevent herpes lesions during your pregnancy, so that you do not have a genital lesion when your baby is born.

Valacyclovir can pass into breast milk and may harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

Do not give this medicine to a child without medical advice.

How should I take valacyclovir?

Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Start taking valacyclovir as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters). This medicine might not be as effective if you first start taking it 1 or 2 days after the start of your symptoms.

Some herpes infections need to be treated for longer than others. Use this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Skipping doses may increase the risk of your virus becoming resistant to antiviral medicine.

You may take valacyclovir with or without food.

Drink plenty of water while you are taking valacyclovir to keep your kidneys working properly.

Lesions caused by herpes viruses should be kept as clean and dry as possible. Wearing loose clothing may help to prevent irritation of the lesions.

Store valacyclovir tablets at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking valacyclovir?

Taking this medicine will not prevent you from passing genital herpes to other people. Herpes infections are contagious and you can infect other people even while you are taking with valacyclovir.

Avoid sexual intercourse or use a latex condom to help keep you from spreading the virus to others. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent the spread of infection.

Do not share this medicine with another person, even if they have the same symptoms you have.

Valacyclovir side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • confusion, aggression, or you feel shaky or unsteady;

  • hallucinations (seeing or hearing things that are not real);

  • problems with speech;

  • a seizure (convulsions); or

  • kidney problems--little or no urination, painful or difficult urination, swelling in your feet or ankles, feeling tired or short of breath.

Stop taking valacyclovir and call your doctor right away if you have any of the following signs of a serious side effect that can harm red blood cells:

  • fever, pale skin;

  • unusual bleeding (nosebleeds, bleeding gums);

  • red or pink urine, little or no urination;

  • red spots on the skin (not related to herpes or chickenpox);

  • feeling weak or tired;

  • stomach pain, bloody diarrhea, vomiting; or

  • swelling in your face, hands, or feet.

Side effects may be more likely in adults who are 65 or older.

Common side effects may include:

  • nausea, stomach pain;

  • headache;

  • rash; or

  • tired feeling.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

See also: Side effects (in more detail)

What other drugs will affect valacyclovir?

Valacyclovir can harm your kidneys. This effect is increased when you also use certain other medicines, including: antivirals, chemotherapy, injected antibiotics, medicine for bowel disorders, medicine to prevent organ transplant rejection, injectable osteoporosis medication, and some pain or arthritis medicines (including aspirin, Tylenol, Advil, and Aleve).

Other drugs may interact with valacyclovir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

Where can I get more information?

  • Your pharmacist can provide more information about valacyclovir.
  • Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
  • Disclaimer: Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2012 Cerner Multum, Inc. Version: 10.01.

Date modified: October 14, 2016
Last reviewed: December 07, 2015