Valacyclovir

pronounced as (val ay sye' kloe veer)

Brand Name(s): Valtrex®, also available generically
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Why is this medicine prescribed?

Valacyclovir is used to treat certain viral infections including

  • herpes labialis (cold sores)
  • varicella infections including herpes zoster (shingles) and chicken pox)
  • genital herpes (a sexually transmitted infection)
It is in a class of medications called antivirals. It works by stopping the spread of the herpes virus in the body.

Valacyclovir helps treat and control outbreaks of genital herpes but should be used with safe sexual practices. Valacyclovir will not cure genital herpes.

Are there other uses for this medicine?

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

How should this medicine be used?

Valacyclovir comes as a tablet to take by mouth with or without food. It is 1 to 3 times a day depending on the condition being treated.

  • for cold sores: take 2 doses twelve hours apart
  • for shingles and chickenpox: take every 8 hours for 7 days
  • to treat genital herpes: take twice a day for as long as your doctor tells you to take the medication
  • to prevent outbreaks and stop the spread of genital herpes: take once or twice daily

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.

Continue to take valacyclovir even if you feel well. Do not stop taking valacyclovir without talking to your doctor.

Ask your pharmacist or doctor for a copy of the manufacturer's information for the patient.

What special precautions should I follow?

Before taking valacyclovir,

  • tell your doctor or pharmacist if you are allergic to this drug, any part of this drug, or any other drugs, foods or substances. Tell your doctor or pharmacist about the allergy and what symptoms you had.
  • tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take.
  • tell your doctor if you have or have ever had problems with your immune system, human immunodeficiency virus infection (HIV) or acquired immunodeficiency syndrome (AIDS), a bone marrow transplant, a kidney transplant, or kidney or liver disease.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking valacyclovir, call your doctor.

What special dietary instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do if I forget to take a dose?

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

What should I do in case of overdose?

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help . If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

What side effects can this medicine cause?

Valacyclovir may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • headache
  • nausea, vomiting, diarrhea, abdominal pain

Some side effects can be serious. If you experience any of the following side effects, call your doctor immediately or get emergency medical treatment:

  • rash, blisters, sores in the mouth, blisters, or peeling of the skin
  • confusion, aggressiveness, unsteady or shaky movements, problems with speech, seizures, or seeing or hearing things that are not real, seizures, coma
  • fever
  • tiredness, decreased urination, swelling of the legs, ankles, and feet
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online ( https://www.fda.gov/Safety/MedWatch ) or by phone ( 1-800-332-1088).

What should I know about storage and disposal of this medication?

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 (not in the bathroom).

Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location – one that is up and away and out of their sight and reach. https://www.upandaway.org Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website https://goo.gl/c4Rm4p for more information.

What other information should I know?

Keep all appointments with your doctor and the laboratory.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription. If you still have symptoms of infection after you finish the valacyclovir, call your doctor.

Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS ® Patient Medication Information™. © Copyright, 2026. The American Society of Health-System Pharmacists ® , 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: April 15, 2026.