Valacyclovir Valtrex is used to treat outbreaks of herpes. An antiviral medication, Valtrex slows production of the herpes virus, which can help relieve pain, shorten outbreaks and prevent future outbreaks. The tablet can be taken daily for long-term treatment or as a multi-day course for immediate short-term treatment. Read more about cold sores.
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Valtrex is also available as a treatment for genital herpes
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How to use this information 
This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective or appropriate for you. This information is not individual medical advice and does not substitute for the advice of a medical provider. If you have any questions, go to your patient dashboard and request a callback for complete information about this product and your specific health needs.
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What you should know about Valacyclovir
  • Valacyclovir is used to treat infections caused by certain types of viruses. In children, it is used to treat cold sores around the mouth (caused by herpes simplex) and chickenpox (caused by varicella zoster). In adults, it is used to treat shingles (caused by herpes zoster) and cold sores around the mouth.
  • Valacyclovir is also used to treat outbreaks of genital herpes. In people with frequent outbreaks, this medication is used to reduce the number of future episodes.
  • Valacyclovir is an antiviral drug that stops the growth of certain viruses. However, it is not a cure for these infections. The viruses that cause these infections continue to live in the body, even between outbreaks. Valacyclovir decreases the severity and length of these outbreaks. It helps the sores heal faster, keeps new sores from forming and decreases pain/itching. This medication may also help reduce how long pain remains after the sores heal.
How to take Valacyclovir
  • Read the Patient Information Leaflet if available from your pharmacist before you start taking Valacyclovir and each time you get a refill. If you have any questions, request a medical callback.
  • Take Valacyclovir by mouth, with or without food, as directed by your medical provider. Drink plenty of fluids while taking this medication to lower the chance of side effects.
  • The dosage and length of treatment are based on your type of infection, medical condition and response to treatment. For treating chickenpox in children, the dosage is also based on weight.
  • This medication works best when started at the first sign of an outbreak, as directed by your medical provider. It may not work as well if you delay treatment. For shingles or chickenpox, start taking Valacyclovir at the first symptom or as soon as possible after the rash appears. For cold sores or genital herpes, start taking this medication at the first sign or as soon as you feel tingling, itching or burning.
  • Valacyclovir works best when the amount of medicine in your body is kept at a constant level. Take this drug at evenly spaced intervals. To help you remember, take it at the same time(s) each day.
  • Continue to take this medication until the full prescribed amount is finished. Do not change your dose, skip doses or stop this medication early without your medical provider's approval. 
  • Tell your medical provider if your condition continues or gets worse.
Potential side effects
  • Nausea, stomach pain, headache or dizziness may occur. If any of these effects last or get worse, tell your medical provider or pharmacist promptly.
  • Remember that this medication has been prescribed because your medical provider has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not experience serious side effects.
  • Tell your medical provider right away if you have any serious side effects, including:

    • Mental or mood changes, such as agitation, confusion or hallucinations
    • Trouble speaking
    • Shaky or unsteady movements
    • Signs of kidney problems, such as a change in the amount of urine
  • This medication may rarely cause a life-threatening disorder that affects the blood cells, kidneys and other parts of the body. This disorder is more likely to occur if you have conditions related to a weakened immune system, such as HIV disease, bone marrow transplant or kidney transplant. Get medical help right away if you have any serious side effects, including:

    • Extreme tiredness
    • Slow, fast or irregular heartbeat
    • Easy bruising or bleeding
    • New fever
    • Bloody or dark urine
    • Severe stomach or abdominal pain
    • Yellowing eyes or skin
    • Sudden vision changes
    • Loss of consciousness
    • Seizures
  • A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

    • Rash
    • Itching or swelling, especially of the face/tongue/throat
    • Severe dizziness
    • Trouble breathing
  • This is not a complete list of possible side effects.If you notice other effects not listed above, request a callback for medical advice. You may also report side effects to the FDA at 1-800-FDA-1088 or at

Precautions to be aware of
  • Before taking Valacyclovir, tell your medical provider or pharmacist if you are allergic to it or Acyclovir,  or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Request a callback for more details.
  • Before using this medication, tell your medical provider or pharmacist your medical history, especially of kidney problems.
  • In rare cases, Valacyclovir may make you dizzy. Alcohol or marijuana (cannabis) can exacerbate the effect. Do not drive, use machinery or do anything that requires alertness until you can do it safely. Limit alcoholic beverages. Talk to your medical provider if you are using marijuana (cannabis).
  • Before having surgery, tell your doctor or dentist about all the products you use, including prescription drugs, nonprescription drugs and herbal products.
  • Do not get certain immunizations/vaccinations, such as vaccines against the varicella virus, without the consent of your medical provider.
  • Older adults may be more sensitive to the side effects of this drug, especially mental/mood changes—such as confusion or agitation—and kidney problems like a change in the amount of urine.
  • Cold sores can spread easily. Avoid close physical contact with others (such as kissing) during an outbreak until the cold sores have completely healed. Try not to touch the cold sore. If you do, wash your hands afterward.
  • Valacyclovir does not prevent the spread of herpes. To lower the chance of giving genital herpes to your partner, do not have sexual contact during an outbreak or if you have symptoms. You can spread genital herpes even if you do not have symptoms. Always use an effective barrier method, such as latex or polyurethane condoms/dental dams, during all sexual activity. Consult your medical provider or pharmacist for more details.
  • During pregnancy, this medication should be used only when there is a clear need. Discuss the risks and benefits with your medical provider.
  • This medication passes into breast milk, but is unlikely to harm a nursing infant. Consult your medical provider before breastfeeding.
Drug interactions
  • Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use—including prescription/nonprescription drugs and herbal products—and share it with your medical provider and pharmacist. Do not start, stop or change the dosage of any medicines without your medical provider's approval.
  • Other drugs that may cause kidney problems—including nonsteroidal anti-inflammatory drugs (NSAIDs) such as Ibuprofen and Naproxen—may interact with Valacyclovir. 
  • Valacyclovir is very similar to Acyclovir. Do not use medications containing Acyclovir while using Valacyclovir.
What to do in the event of an overdose

If someone has overdosed and has serious symptoms, such as passing out or trouble breathing, call 911. If symptoms from taking this medication are less severe, call your local poison control center at 1-800-222-1222 right away.

Symptoms of overdose may include:

  • Change in the amount of urine
  • Extreme tiredness
  • Mental or mood changes
  • Loss of consciousness
  • Seizure
Additional notes

Do not share this medication with others. This medication has been prescribed for your current condition only. Do not use it later for another infection unless your prescribing doctor tells you to.

What to do if you miss a dose
  • If you miss a dose, take it as soon as you remember. 
  • If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. 
  • Do not double the dose to catch up.
How to store this medication
  • Store at room temperature away from light and moisture. Do not store in the bathroom. 
  • Keep all medications away from children and pets.
  • Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.
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