Acyclovir

Written by Rosanna Sutherby, PharmD
Medically reviewed by Melissa Badowski, PharmD, MPH, FCCP
Updated on June 16, 2023

Specifically, the Food and Drug Administration (FDA) has approved acyclovir to treat the following conditions in adults and some children:

• herpes zoster (shingles)
• genital herpes
• cold sores
• chickenpox
• encephalitis and other serious infections caused by the herpes simplex and varicella-zoster viruses

Acyclovir is also approved to help prevent genital herpes from coming back.

These approved uses differ based on the form of acyclovir your doctor prescribes.

This article describes acyclovir’s uses, side effects, and more. Below you’ll also find some coupon options to help save on the cost of acyclovir.

The Food and Drug Administration (FDA) approves prescription drugs such as acyclovir for certain conditions. Approved uses for acyclovir are described below. These uses differ based on the form of acyclovir prescribed.

Use for cold sores

Doctors may prescribe acyclovir topical cream for treating cold sores caused by the herpes simplex virus. (Topical means the drug is applied to your skin.) Acyclovir is used for this purpose in adults and children ages 12 years and older. It’s usually prescribed as a short-term treatment.

Cold sores are caused by an infection with the herpes simplex virus. This virus can be passed from one person to another if they come in contact with unhealed cold sores.

With cold sores, you may have small, fluid-filled blisters on your lips or around your mouth. In addition to blisters, you may have other symptoms, including:

• tingling or burning sensation around the blistered area
• fever
• fatigue (low energy)

Doctors may not prescribe acyclovir topical cream in certain situations, such as for herpes infections inside your eyes, nose, or mouth.

Use for shingles

Doctors may prescribe the following forms of acyclovir for treating herpes zoster (shingles):

• oral tablet
• oral capsule
• oral liquid suspension (a type of liquid mixture)
• liquid solution for injection

Oral forms of acyclovir are prescribed for this purpose in adults and children ages 2 years and older. Acyclovir injection may be prescribed for children of any age for this purpose.

Shingles is an infection caused by the varicella-zoster virus. This is the same virus that causes chickenpox, but it typically affects adults ages 50 years and older.

With shingles, you may have a red, dark pink, dark brown, or purple painful skin rash. Typically, shingles appears as a band of blisters on one side of your body. It can occur on your face, neck, or torso. Other symptoms you may experience with shingles include fever, fatigue, headache, or muscle weakness.

Uses for genital herpes

Doctors may prescribe the following forms of acyclovir for treating genital herpes:

• oral tablet
• oral capsule
• oral liquid suspension
• topical ointment
• liquid solution for injection

The oral tablet, oral capsule, and oral liquid suspension forms of acyclovir are also prescribed to help prevent genital herpes from returning.

Acyclovir injection is prescribed for these purposes in adults and children 12 years and older. The topical ointment is used only in adults. All the other forms approved for these purposes are used in adults and children ages 2 years and older.

The drug is usually prescribed as a short-term treatment for genital herpes. But if your doctor prescribes acyclovir to help prevent genital herpes from coming back, you may take it long term.

Genital herpes is caused by an infection with the herpes simplex virus. With genital herpes, you may have blisters in your genital areas, anus, or buttocks. The blisters may break open and ooze liquid.

Other symptoms you may have include:

• itching or tingling in the area before blisters appear
• fever
• headache
• swollen lymph glands

Use for certain other viral infections

Doctors may prescribe acyclovir oral tablet, oral capsule, and oral liquid suspension for treating chickenpox. It’s used for this purpose in adults and children ages 2 years and older. It’s usually prescribed as a short-term treatment.

Chickenpox is caused by an infection with the varicella-zoster virus. This is the same virus that causes shingles. Chickenpox typically causes red or discolored, itchy blisters all over your body. Other symptoms can include headache, fever, or loss of appetite.

Acyclovir liquid solution for injection can be prescribed to treat serious infections caused by the herpes simplex and varicella-zoster viruses. This includes encephalitis (inflammation of the brain) caused by herpes simplex. It also includes infections in newborns and people with a weakened immune system.

Below you’ll find answers to a few commonly asked questions about acyclovir.

What brand names are available for acyclovir?

Acyclovir is available as the brand names Zovirax and Sitavig.

Zovirax comes in a topical ointment and cream. Sitavig comes in a tablet that you dissolve inside your cheek. But this form is not available as a generic drug.

Talk with your doctor if you have questions about brand-name versions of acyclovir.

Is acyclovir available over the counter?

No, acyclovir is not available over the counter (OTC). You need a prescription from your doctor or another healthcare professional to get acyclovir.

If you have a cold sore, OTC medications are available for use. Be sure to talk with your doctor or pharmacist before taking or using any OTC medications. They can advise whether they’re safe for you.

How does acyclovir work? And how long does it take to start working?

Acyclovir works by blocking the herpes simplex and varicella-zoster viruses from multiplying (making more virus) in your body. This helps your immune system fight the virus.

How long it takes for acyclovir to work can depend on several factors. These include when you start taking the medication and what form you use. Acyclovir usually works faster if you take it within 48–72 hours of having symptoms. And acyclovir injection usually works faster than the other forms of the drug.

Keep in mind that acyclovir does not cure viral infections. Taking or using acyclovir can prevent the virus from multiplying, but it doesn’t kill it completely. This means that your symptoms may return in the future even after treating your current infection.

Talk with your doctor if you have concerns about your acyclovir treatment.

Acyclovir may cause mild or serious side effects. More common mild side effects of acyclovir and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age, overall health, and any other medications you take.

To learn more about acyclovir’s side effects, see this article or ask your doctor or pharmacist. You can also read the prescribing information for acyclovir in the “Article resources” section.

Mild side effects

More common mild side effects reported with some forms of acyclovir are listed below. These side effects may differ based on the form of acyclovir you take or use.

This article doesn’t include all possible mild side effects of the drug. To learn more about acyclovir’s side effects based on the form, see the prescribing information for acyclovir in the “Article resources” section.

With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects are bothersome, tell your doctor or pharmacist. They may be able to suggest ways to manage them.

Acyclovir topical ointment’s mild side effects include the following at the site of application:

• mild pain
• temporary burning
• temporary stinging
• itchiness
• mild allergic reaction*

Acyclovir oral tablet’s mild side effects include:

• nausea
• vomiting
• diarrhea
• headache
• mild allergic reaction*

* For details about this side effect, see the “Interactions and warnings for acyclovir” section.

Serious side effects

Serious side effects of acyclovir are listed below. These side effects may differ based on the form of acyclovir you take or use.

This article doesn’t include all possible serious side effects of the drug. To learn more about acyclovir’s side effects based on the form, see the prescribing information for acyclovir in the “Article resources” section.

With many drugs, serious side effects are possible but not common. If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.

In general, acyclovir’s serious side effects include:

• tiny blood clots throughout the body
• swelling under the skin
• severe allergic reaction*

* For details about this side effect, see the “Interactions and warnings for acyclovir” section.

Below, you’ll find information about acyclovir’s possible interactions and warnings.

Interactions of acyclovir

Certain things may affect how a drug works. These include getting vaccines, consuming alcohol or certain foods, or taking the drug with other medications. This effect is called a drug interaction.

Before you take or use acyclovir, ask your doctor to check for possible interactions. Be sure to tell them about any of the following you take or use:

• prescription drugs
• over-the-counter medications
• vitamins, herbs, or supplements

To learn about drug-condition interactions, see the “Warnings for acyclovir” section.

Warnings for acyclovir

Some people should not take or use acyclovir, and others should take or use it cautiously.

Acyclovir could cause harm to people with certain health conditions. This effect is called a drug-condition interaction. Other factors can also affect whether acyclovir is a safe option for you. These warnings may differ based on the form of acyclovir you use.

Ask your doctor about specific warnings for acyclovir, and be sure to tell your doctor about your:

• current health, including any allergies to medications
• past health conditions or surgeries

Allergic reaction

Acyclovir can cause an allergic reaction in some people. Severe allergic reactions are rare but possible.

If you’ve had an allergic reaction to acyclovir or any of its ingredients, your doctor will likely not prescribe acyclovir. They can tell you about medications that are safer options for you.

A mild allergic reaction may cause the following symptoms:

• skin rash
• itchiness
• flushing (temporary warmth, redness, or deepening of skin color)

A severe allergic reaction may cause the following symptoms:

• swelling under your skin, usually in your hands, feet, eyelids, or lips
• swelling of your mouth, throat, or tongue, which can cause breathing problems

If you have an allergic reaction to acyclovir, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.

Overdose of acyclovir

You should not take or use more acyclovir than your doctor prescribes. For some drugs, doing so may lead to harmful effects or overdose.

If you think you’ve taken or used too much acyclovir, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have concerning symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

Pregnancy or breastfeeding and acyclovir

Information about acyclovir and pregnancy and breastfeeding is described below.

Acyclovir and pregnancy

It’s not known whether acyclovir should be used during pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before using this medication.

Acyclovir and breastfeeding

It’s not known whether acyclovir should be used while breastfeeding. If you’re breastfeeding or planning to do so, talk with your doctor before using this medication.

This article describes acyclovir’s uses and dosage, ways to save on cost, and more. Let your doctor know if you have questions about acyclovir or would like more details about it.

Here’s a list of some possible questions you may want to ask your doctor:

• How long will I need to take acyclovir to help prevent symptoms from coming back?
• How do the side effects of acyclovir compare with those of valacyclovir (Valtrex)?
• Will my dosage change if I have kidney problems?

• Acyclovir — acyclovir capsule (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/f87c2c1e-568f-49e1-979e-fce80086fe08/spl-doc
• Acyclovir — acyclovir cream (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/a2966b6d-c6c0-4afd-8eda-045df497cb9d/spl-doc
• Acyclovir — acyclovir injection, solution. (2021). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/69a98000-adef-4323-89a7-09e035a257d4/spl-doc
• Acyclovir — acyclovir ointment. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/c11c1136-7421-48ff-86d2-39507e80a04c/spl-doc
• Acyclovir — acyclovir suspension. (2022). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/62bdcf22-51f3-4c81-9bd4-a2dc48bec580/spl-doc
• Acyclovir — acyclovir tablet. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/b004baf0-3178-4ced-9917-be87d0b4e833/spl-doc
• Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm

Disclaimer: Optum Perks 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 another 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.