Valacyclovir | Side Effects, Dosage, Uses & More
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Generic Name:

valacyclovir, Oral tablet

All Brands

  • Valtrex
SECTION 1 of 5

Highlights for valacyclovir

Oral tablet
1

Valacyclovir is used to treat viral infections caused by a group of viruses called herpes simplex viruses. It’s used to treat cold sores (oral herpes), shingles, or chicken pox. It’s also used to treat or prevent flare-ups of genital herpes.

2

This drug comes in the form of a tablet you take by mouth.

3

Valacyclovir is available as a brand-name drug called Valtrex. It’s also available as a generic drug.

4

The more common side effects of valacyclovir can include headache, nausea, vomiting, dizziness, or pain in the abdomen (stomach area).

5

This drug does not cure herpes infections. The herpes virus can stay in your body for a long time. This drug can help prevent re-infection at a later time.

6

Using this medication daily may help lower the risk of spreading this disease to your sexual partner. However, you should not have sexual contact with your partner when you have any symptoms of an outbreak of genital herpes. Even if you use safer sex practices, you can still spread genital herpes. Talk with your doctor for more information about how to have safer sex.

IMPORTANT INFORMATION

Blood disorders

For certain people, this drug can cause thrombocytopenic purpura (TTP)/ hemolytic uremic syndrome (HUS). These conditions cause a severely low level of red blood cells and platelets in your body. TTP/HUS can result in death. You’re at risk of these problems if you’ve had a bone marrow or a kidney transplant. You’re also at risk if you have advanced human immunodeficiency virus (HIV) or AIDS.

Kidney failure

In some cases, this drug can cause your kidneys to stop working. This can occur if you’re on a high dose of this medication and have existing kidney problems. It can also occur if you’re taking other drugs that can harm your kidneys, if you’re not well hydrated, or if you’re over the age of 65 years.

Effects on the central nervous system

If you have kidney disease or use this drug at higher doses than your doctor prescribes, it can build up in your body. High levels of this drug can cause serious side effects that impact your brain. Symptoms can include hallucinations (seeing or hearing things that aren’t real) or delusions (believing things that aren’t true). They can also include agitation, confusion, or seizures. If you have any of these side effects, stop taking this drug. Call 9-1-1 right away or go to the nearest emergency room.

Drug features

This drug is a prescription drug. It comes in the form of a tablet you take by mouth.

Valtrex is a brand-name drug. It’s also available as a generic drug. Generic drugs usually cost less. In some cases, they may not be available in every strength or form as the brand-name version. Talk to your doctor to see if the generic version will work for you.

This drug may be used as part of a combination therapy. This means you may need to take it with other medications.

Why it's used

This drug is used to treat viral infections caused by a group of viruses called herpes simplex viruses. These infections include oral and genital herpes, shingles, and chicken pox.

More Details

How it works

This drug belongs to a class of drugs called anti-viral drugs. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

More Details

Why it's used

This drug is used to treat viral infections caused by a group of viruses called herpes simplex viruses. These infections include oral and genital herpes, shingles, and chicken pox.

  • Oral herpes causes cold sores. These are small, painful sores that you can get in or around your mouth. Cold sores can be spread by kissing or other physical contact with the infected area of the skin.
  • Genital herpes is a sexually transmitted disease. This means it’s spread through sexual contact. Symptoms include small, painful blisters on the genital area. You can spread genital herpes to your sexual partner even when you don’t have any symptoms.  This drug is used to treat or prevent flare-ups of genital herpes in people with normal immune systems, or in people with HIV.
  • Shingles is caused by the same virus that causes chicken pox (varicella zoster). Symptoms of shingles include small, painful blisters that appear on the skin. Shingles can occur in people who have already had chicken pox. It can also spread to people who have not had chicken pox before through contact with the infected skin.
  • Chicken pox causes an itchy rash of small, red bumps that can look like pimples or insect bites. The rash can spread almost anywhere on the body. Chicken pox can also cause flu-like symptoms, such as fever or tiredness. This drug is used to treat chicken pox in children ages 2–18 years who have a normal immune system.

How it works

This drug belongs to a class of drugs called anti-viral drugs. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

The herpes virus spreads in your body by creating more of its cells. This drug works by making it harder for the herpes virus to multiply (make more cells) in your body.

This drug does not cure herpes infections, which include cold sores, chicken pox, shingles, and genital herpes. The herpes virus may still live in your body after treatment. The infection may occur again at a later time even after the symptoms of the first infection are gone.

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valacyclovir Side Effects

Oral tablet

More Common Side Effects

The more common side effects of valacyclovir can include:

  • headache

  • nausea

  • vomiting

  • dizziness

  • pain in the abdomen (stomach area)

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious Side Effects

Call your doctor right away if you have serious side effects. Call 9-1-1 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Kidney failure. Symptoms can include:

    • severe drowsiness
    • urinating less than usual
    • swelling in the legs, ankles, or feet
  • Unusual mood or behavior. Symptoms can include:

    • aggressive behavior
    • unsteady or shaky movements
    • confusion
    • hallucinations
    • seizures
    • coma
Pharmacist's Advice
Healthline Pharmacist Editorial Team

This drug doesn’t cause drowsiness.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.
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valacyclovir May Interact with Other Medications

Oral tablet

An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well. To help prevent interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking.

To find out how valacyclovir might interact with something else you’re taking, talk to your doctor or pharmacist.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

People with kidney problems

Your kidneys clear this drug from your body. If you have kidney problems or a history of kidney disease, you may not be able to clear it from your body. This may increase the levels of the drug in your body and cause more side effects. This drug can also make your kidney function worse. To help prevent these problems, your doctor may prescribe you a lower dosage of this drug.

People with advanced HIV or a history of transplant

If you have advanced HIV (human immunodeficiency virus) or a history of bone marrow or kidney transplant, you may be at a higher risk of certain blood disorders. These conditions are called thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). They can result in severely low red blood cells and platelets in your body. TTP/HUS can cause death.

Pregnant women

This drug is a category B pregnancy drug.

That means two things:

  1. Research in animals has not shown a risk to the fetus when the mother takes the drug.
  2. There aren’t enough studies done in humans to show if the drug poses a risk to the fetus.

Talk to your doctor if you’re pregnant or planning to become pregnant. Animal studies do not always predict the way humans would respond. Therefore, this drug should only be used in pregnancy if clearly needed.

Women who are breast-feeding

This drug may pass into breast milk and may cause side effects in a child who is breast-fed.

Talk to your doctor if you breast-feed your child. You may need to decide whether to stop breast-feeding or stop taking this medication.

For seniors

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

For children

This drug has not been studied for use in treatment or prevention of herpes simplex virus (HSV) infection in newborn babies. The following are other age limitations for use of this drug:

  • Oral herpes (cold sores): This drug has been studied and approved for treatment of cold sores in children ages 12 years and older.
  • Genital herpes: This drug has not been studied or approved for treatment of genital herpes in children younger than 18 years.
  • Shingles: This drug has not been studied or approved for treatment of shingles in children younger than 18 years.
  • Chicken pox: This drug has been studied and approved for treatment of chicken pox in children 2–18 years of age. This drug has not been studied or approved for treatment in children younger than 2 years of age.

When to call the doctor

Call your doctor right away if you become pregnant while taking this drug.

Allergies

This drug can cause a severe allergic reaction. Symptoms can include:

  • trouble breathing
  • swelling of your throat or tongue 

If you have an allergic reaction, call your doctor or local poison control center right away. If your symptoms are severe, call 9-1-1 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to this drug or acyclovir. Taking it again could be fatal (cause death).

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How to Take valacyclovir (Dosage)

Oral tablet

All possible dosages and drug forms may not be included here. Your dosage, drug form, and how often you take the drug will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

What are you taking this medication for?

Oral herpes

Brand: Valtrex

Form: Oral tablet
Strengths: 500 mg, 1 g
Adult dosage (ages 18–64 years)

Typical dosage: 2 g, twice per day for 1 day, taken 12 hours apart. Treatment should be started at the first sign of cold sore symptoms (such as tingling, itching, or burning).

Child dosage (ages 12–17 years)

Typical dosage: 2 g, twice per day for 1 day, taken 12 hours apart. This drug should be started at the first sign of cold sore symptoms (such as tingling, itching, or burning).

Child dosage (ages 0–11 years)

This drug has not been studied or approved for treatment of oral herpes in children younger than 12 years.

Senior dosage (ages 65 years and older)

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

Your doctor may start you on a lowered dose or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Genital herpes

Brand: Valtrex

Form: Oral tablet
Strengths: 500 mg, 1 g
Adult dosage (ages 18–64 years)
  • First episode: 1 g, taken twice per day for 10 days. This drug works best if it’s started within 48 hours of when the first symptom appears.
  • Repeating episodes: 500 mg, taken twice per day for 3 days. Treatment should be started when the first symptom appears.
  • For preventing flare-ups in people with a normal immune system: 500 mg to 1 g, taken once per day.
  • For preventing flare-ups in people with HIV: 500 mg, taken twice per day.
  • For reducing the risk of transmission to a sexual partner: 500 mg, taken once per day.
Child dosage (ages 0–17 years)

This drug has not been studied for the treatment of genital herpes in children younger than 18 years.

Senior dosage (ages 65 years and older)

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

Your doctor may start you on a lowered dose or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Shingles

Brand: Valtrex

Form: Oral tablet
Strengths: 500 mg, 1 g
Adult dosage (ages 18–64 years)

Typical dosage: 1 g, taken 3 times per day for 7 days. Treatment should be started when the first symptom appears. This drug works best if it’s started within 48 hours of the first sign of a rash on the skin.

Child dosage (ages 0–17 years)

This drug has not been studied for the treatment of shingles in children younger than 18 years.

Senior dosage (ages 65 years and older)

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

Your doctor may start you on a lowered dose or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Chicken pox

Brand: Valtrex

Form: Oral tablet
Strengths: 500 mg, 1 g
Adult dosage (ages 18–64 years)

Typical dosage: 1 g, taken 3 times per day for 7 days. Treatment should be started when the first symptom appears. This drug works best if it’s started within 48 hours of the first sign of a rash on the skin.

Child dosage (ages 2–18 years)
  • Typical dosage: 20 mg per kilogram of the child’s body weight, taken 3 times per day for 5 days.
  • Maximum dosage: 1 g, taken 3 times per day.
Child dosage (ages 0–1 years)

This drug has not been studied or approved for treatment of chicken pox in children younger than 2 years.

Senior dosage (ages 65 years and older)

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

Your doctor may start you on a lowered dose or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.
Pharmacist's Advice
Healthline Pharmacist Editorial Team

This drug comes with serious risks if you don’t take it as prescribed.

If you stop taking the drug suddenly or don’t take it at all

The symptoms of your viral infection may not get better, or may get worse.

If you miss doses or don’t take the drug on schedule

Your medication may not work as well or may stop working completely. If you’re taking this drug to prevent flare-ups of the infection, a certain amount needs to be in your body at all times. You should not stop taking this drug unless your doctor tells you to stop.

If you take too much

You could have dangerous levels of the drug in your body. Symptoms of an overdose of this drug can include more severe side effects, such as:

  • headache
  • nausea
  • tiredness
  • dizziness
  • diarrhea
  • constipation
  • weakness or lack of energy

If you think you’ve taken too much of this drug, call your doctor or local poison control center. If your symptoms are severe, call 9-1-1 or go to the nearest emergency room right away.

What to do if you miss a dose

Take your dose as soon as you remember. But if you remember just a few hours before your next scheduled dose, take only one dose. Never try to catch up by taking two doses at once. This could result in dangerous side effects.

How to tell if the drug is working

Your signs and symptoms from the viral infection should improve.

This drug is used for short-term treatment of oral herpes, genital herpes, shingles, or chicken pox.

This drug is used for long-term treatment to prevent genital herpes, and to treat  genital herpes that recurs (comes back).

Important considerations for taking this drug
take with or without food You can take this drug with or without food See Details
timing Take this drug at the time(s) recommended by your doctor
can crush or cut You can cut or crush the tablet
storage Store this drug carefully See Details
refillable A prescription for this medication is refillable See Details
travel Travel See Details
clinical monitoring Clinical monitoring See Details
not usually stocked Not every pharmacy stocks this drug. When filling your prescription, be sure to call ahead.
hidden costs Hidden costs See Details
insurance Insurance See Details

You can take this drug with or without food

Taking it with food may help reduce any upset stomach.

Store this drug carefully

  • Store it at room temperature between 59°F and 77°F (15°C and 25°C).
  • Keep this drug away from light.
  • Don’t store this medication in moist or damp areas, such as bathrooms.

A prescription for this medication is refillable

You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport x-ray machines. They can’t hurt your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled box with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Clinical monitoring

You and your doctor should monitor certain health issues. This can help make sure you stay safe while you take this drug. These issues include:

  • Kidney function. Blood tests can check how well your kidneys are working. If your kidneys aren’t working well, your doctor may lower your dose of this drug.
  • Mental health and behavioral problems. You and your doctor should watch for any unusual changes in your behavior and mood. This drug can cause new mental health and behavior problems. It can also worsen problems you already have.

Hidden costs

You may need to have blood tests during your treatment with this drug. The cost of these tests will depend on your insurance coverage.

Insurance

Many insurance companies require a prior authorization for this drug. This means your doctor will need to get approval from your insurance company before your insurance company will pay for the prescription.

Are there any alternatives?

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other drug options that may work for you.

What does the pill look like?

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How Much Does valacyclovir Cost?

Oral tablet

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Lowest price for valacyclovir

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These prices represent the lowest priced national pharmacies for valacyclovir on GoodRx. They may be lower than your insurance.

Content developed in collaboration with University of Illinois-Chicago, Drug Information Group

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on November 11, 2015

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
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