Health Guide

Valacyclovir (By mouth)

Valacyclovir (val-ay-SYE-kloe-vir)

Treats herpes virus infections, including shingles, cold sores, and genital herpes. This medicine will not cure herpes, but may prevent a breakout of herpes sores or blisters. Also treats chicken pox.

Brand Name(s):

Valtrex, valACYclovir HCl AvPak

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. Do not use it if you had an allergic reaction to valacyclovir or acyclovir.

How to Use This Medicine:


  • Your doctor will tell you how much medicine to use. Do not use more than directed.
  • This medicine works best when you take it at the first sign of a herpes breakout.
  • Drink extra fluids so you will urinate more often and help prevent kidney problems.
  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Store the oral liquid in the refrigerator. Discard any unused medicine after 28 days.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding, or if you have kidney disease, HIV or AIDS, or had a bone marrow or kidney transplant.
  • This medicine may cause the following problems:
    • Kidney problems
    • Nervous system problems
    • Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (in patients who have HIV or had a bone marrow or kidney transplant)
  • Do not have sex while you have herpes sores. Valacyclovir will not stop the spread of herpes during sex.
  • Even if you have no signs of a herpes infection, it is still possible to spread the virus to others. Always use condoms made from latex or polyurethane when you have sexual contact.
  • Call your doctor if your symptoms do not improve or if they get worse.
  • Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.
  • Do not stop using this medicine suddenly, or change how you take it, without talking to your doctor.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Confusion, agitation, depression, or other behavior changes
  • Decrease in how much or how often you urinate
  • Fast heartbeat, fainting, or extreme weakness
  • Pinpoint red spots on your skin, unusual bleeding or bruising, blood in your urine or stools
  • Problems with walking, speaking, or coordination, seeing or hearing things that are not there
  • Seizures or tremors
  • Yellow skin or eyes

If you notice these less serious side effects, talk with your doctor:

  • Headache or dizziness
  • Nausea, vomiting, diarrhea, stomach pain

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 7/4/2018
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