Valacyclovir is a medicine used to treat or prevent genital herpes and shingles (herpes zoster) in adults.

It’s also given to treat cold sores in adults and children who are at least 12 years old. Additionally, valacyclovir is used as a therapy for children with chickenpox who are between ages 2 and 18.

Valacyclovir is an antiviral drug that won’t cure an infection like herpes, but can improve symptoms.

The U.S. Food and Drug Administration (FDA) approved this medicine in 1995. It’s sold under the brand name Valtrex.

uses

What is Valtrex (Valacyclovir) used for?

Herpes Simplex -- Mucocutaneous/Immunocompetent Host
Herpes Simplex -- Mucocutaneous/Immunocompromised Host
Herpes Zoster
Varicella-Zoster
Herpes Zoster -- Prophylaxis
Varicella-Zoster -- Prophylaxis
Infection - Bacterial/Fungal/Protozoal/Viral
Herpes Zoster Iridocyclitis
Herpes Zoster Peripheral Neuropathy
Herpes Zoster Meningitis
Varicella Pneumonitis
Herpes Zoster Otitis Externa
Herpes Simplex Labialis
Herpes Simplex -- Suppression
Herpes Zoster Myelitis

warnings

What is the most important information I should know about Valtrex (Valacyclovir)?

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

Tell your doctor if you have ever had:

kidney disease (or if you are on dialysis);
a weak immune system;
HIV or AIDS; or
a kidney transplant or bone marrow transplant.

Tell your doctor if you are pregnant or plan to become pregnant. Herpes can be passed to your baby during childbirth if you have a genital lesion when your baby is born. If you have genital herpes, it is very important to prevent herpes lesions during pregnancy. Take your medicine as directed to best control your infection.

It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.

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

Side Effects

What are the side effects of Valtrex (Valacyclovir)?

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, agitation, or you feel shaky or unsteady;
hallucinations (seeing or hearing things that are not real);
problems with speech;
a seizure; or
kidney problems--little or no urination, swelling in your feet or ankles, feeling tired or short of breath.

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

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;
purple or 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.

Common side effects may include:

nausea, stomach pain; or
headache.

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.

Pregnancy & Breastfeeding

Can I take Valtrex (Valacyclovir) if I’m pregnant or breastfeeding?

It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.

Interactions

What drugs and food should I avoid while taking Valtrex (Valacyclovir)?

Avoid sexual intercourse or use a latex condom to help keep you from spreading the herpes 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.

Valacyclovir will not prevent the spread of sexually transmitted diseases other than the virus that causes genital herpes.

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

Dosage Guidelines & Tips

How to take Valtrex (Valacyclovir)?

Use Valtrex (Valacyclovir) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Start taking valacyclovir as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters, or rash). This medicine may not be effective if taken after you already have symptoms.

You may take valacyclovir with or without food.

Tell your doctor if a child taking this medicine cannot swallow the valacyclovir tablet.

Your pharmacist may prepare an oral suspension (liquid) form of valacyclovir. Shake this suspension before you measure a dose. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

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.

Some herpes infections need to be treated for longer than others. You may need to take the medicine for only 1 day or for just a few days. To prevent recurrent genital herpes, you may need to take valacyclovir for up to 1 year. Use this medicine for the full prescribed length of time, even if your symptoms quickly improve.

Follow your doctor's dosing instructions very carefully. Taking more valacyclovir than prescribed will not make this medicine more effective.

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

Store at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use.

Store the oral suspension in a refrigerator and throw away suspension any left over after 28 days of use.

What should I do if I missed a dose of Valtrex (Valacyclovir)?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.