Acyclovir Oral Capsule | Side Effects, Dosage, Uses & More
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Generic Name:

acyclovir, Oral capsule

All Brands

  • Zovirax
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Highlights for acyclovir

Oral capsule
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Acyclovir is used to treat viral infections. These include varicella-zoster (shingles), genital herpes, and chickenpox.

2

Acyclovir is available as a tablet, capsule, suspension, and buccal tablet you take by mouth. (Buccal means you place the tablet between your gums and cheek, where it dissolves.) It also comes in a cream and ointment you apply to your skin. It’s also available as an intravenous (IV) drug, which is only given by a healthcare provider.

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The oral tablet is available as the brand-name drug Zovirax. It’s also available as a generic drug.

4

The more common side effects of this drug include nausea, vomiting, diarrhea, headache, and weakness.

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In some cases, acyclovir can cause serious side effects. These include kidney failure and dangerously low levels of red blood cells and platelets.

IMPORTANT INFORMATION

Kidney failure

This drug may cause your kidneys to stop working. Tell your doctor if you have any kidney problems before taking this medication.

Low red blood cells and platelets

This drug may cause thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). Symptoms can include fatigue and low energy. These conditions cause dangerously low levels of red blood cells and platelets in your body. This may be fatal (cause death).

Sexual contact

You shouldn’t have sexual contact with your partner when you have signs of a genital herpes outbreak. This drug does not cure herpes infections. It may help lower the chance of spreading herpes to your partner. However, even with safe sex practices, it’s still possible to spread genital herpes. Talk to your doctor for information about safe sex practices.

What is acyclovir?

Acyclovir is a prescription drug. It’s available as an oral tablet, oral capsule, oral suspension, buccal tablet (a tablet you place between your gums and cheek to dissolve), topical cream, and topical ointment. It’s also available as an intravenous drug, which is only given by a healthcare provider.

The oral capsule is available as the brand-name drug Zovirax. 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.

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

Acyclovir is used to treat viral infections. These include varicella-zoster (shingles), genital herpes, and chickenpox.

This drug doesn’t cure herpes infections. The herpes virus can stay in your body for a long time and cause symptoms again later.

How it works

Acyclovir belongs to a class of drugs called antivirals. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

Acyclovir works by lowering the ability of the herpes virus to multiply in your body. This treats the symptoms of your infection.

More Details

How it works

Acyclovir belongs to a class of drugs called antivirals. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

Acyclovir works by lowering the ability of the herpes virus to multiply in your body. This treats the symptoms of your infection.

However, this drug doesn’t cure herpes infections. Herpes infections include cold sores, chickenpox, shingles, or genital herpes. Even with this drug, the herpes virus may still live in your body. Your symptoms may occur again later even after the symptoms of your current infection go away.

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acyclovir Side Effects

Oral capsule

More Common Side Effects

Some of the more common side effects of acyclovir include:

  • nausea

  • vomiting

  • diarrhea

  • headache

  • weakness

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:

  • Unusual changes in your mood or behavior. Symptoms can include:

    • aggressive behavior
    • unsteady or shaky movements
    • confusion
    • trouble speaking
    • hallucinations (seeing or hearing something that isn’t there)
    • seizures
    • coma (being unconscious for a long time)
  • Decrease in your red blood cells and platelets. Symptoms can include:

    • fatigue
  • Liver problems

  • Muscle pain

  • Skin reactions. Symptoms can include:

    • hair loss
    • rash
    • breaking or loosening of skin
    • hives
    • Stevens-Johnson syndrome. This is a rare, allergic skin reaction.
  • Changes in your vision

  • Kidney failure. Symptoms can include:

    • kidney or flank pain (pain in your side and back)
    • blood in your urine
  • Allergic reaction. Symptoms can include:

    • trouble breathing
    • swelling of your throat or tongue
    • rash
    • hives
Pharmacist's Advice
Healthline Pharmacist Editorial Team

Acyclovir 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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acyclovir May Interact with Other Medications

Oral capsule

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 this drug 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.
Drug warnings
kidney problems
People with kidney problems

If you have kidney problems or a history of kidney disease, you may not be able to clear this drug from your body well. This may increase the levels of this drug in your body and cause more side effects.

This medication may also decrease your kidney function. This means your kidney disease may get worse.

Your doctor will adjust your dose depending on how well your kidneys are working.

pregnant women
Pregnant women

Acyclovir is a category B pregnancy drug. That means two things:

  1. Studies of the drug in pregnant animals have not shown a risk to the fetus.
  2. There aren’t enough studies done in pregnant women to show if the drug poses a risk to the fetus.

Talk to your doctor if you’re pregnant or planning to become pregnant. This drug should be used only if the potential benefit justifies the potential risk to the fetus.

breastfeeding
Women who are breast-feeding

Acyclovir may pass into breast milk and may cause side effects in a child who is breastfed.

Talk to your doctor if you breastfeed your baby. You may need to decide whether to stop breastfeeding or stop taking this medication.

for seniors
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
For children

This drug hasn’t been studied in children younger than 2 years.

call doctor
When to call the doctor

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

allergies
Allergies

Acyclovir can cause a severe allergic reaction. Symptoms can include:

  • trouble breathing
  • swelling of your throat or tongue
  • rash
  • hives 

Call 9-1-1 or go to the nearest emergency room if you develop these symptoms.

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

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How to Take acyclovir (Dosage)

Oral capsule

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?

Shingles, genital herpes, or chickenpox

Generic: acyclovir

Form: Oral solution
Strengths: 200 mg

Brand: Zovirax

Form: Oral solution
Strengths: 200 mg
Adult dosage (ages 18–64 years)
  • Shingles: 800 mg taken every 4 hours, five times per day for 7–10 days
  • Genital herpes:
    • Initial treatment: 200 mg taken every 4 hours, five times per day for 10 days
    • Prevention of recurrent herpes: Take 400 mg twice per day, every day for up to 12 months. Your doctor will decide how long you should take this drug to avoid a flare-up of the infection.
    • Reinfection (flare-up of the infection): Take 200 mg every 4 hours, five times per day for 5 days. You should take this drug as soon as the first signs of a flare-up appear.
  • Chickenpox: Take 800 mg four times per day for 5 days. Start this drug as soon as your first symptom of chickenpox appears. It isn’t known if this drug is effective if you start it more than 24 hours after the first sign of chickenpox.
Child dosage (ages 2–17 years)
  • Children who weigh 40 kg (88 lbs.) or less: 20 mg/kg of body weight, given four times per day for 5 days
  • Children who weigh more than 40 kg: 800 mg four times per day for 5 days

Start this drug as soon as the first symptom of chickenpox appears. It isn’t known if this drug is effective if you start it more than 24 hours after the first sign of chickenpox.

Child dosage (ages 0–1 years)

It hasn’t been confirmed that acyclovir is safe and effective for 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 increases your risk of side effects.

Your doctor may start you on a lowered dose or a different medication 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 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 your infection, a certain amount needs to be in your body at all times. You shouldn’t stop taking this drug without talking to your doctor first.

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.

If you take too much

You could have dangerous levels of the drug in your body and experience more severe side effects.

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.

How to tell if the drug is working

The symptoms of your infection will get better.

Acyclovir is used for short-term treatment for genital herpes, shingles, and chicken pox.

Acyclovir is used for long-term treatment for reoccurring genital herpes.

Important considerations for taking this drug

You can take acyclovir with or without food

Taking it with food may help reduce upset stomach.

Store this drug carefully

  • Store this drug at room temperature. Keep it between 59°F and 77°F (15°C and 25°C).
  • Keep it 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. Your doctor may do blood tests to 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 make problems you already have worse.

Your diet

You should drink plenty of water to stay hydrated. This drug can harm your kidneys if you don’t stay well hydrated.

Sun sensitivity

Acyclovir can make your skin more sensitive to the sun. This increases your risk of sunburn. Avoid the sun if you can. If you can’t, be sure to wear protective clothing and apply sunscreen.

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 acyclovir Cost?

Oral capsule

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Lowest price for acyclovir

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

Show Sources

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 January 21, 2016

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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