Drug information

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Acyclovir
Other Names
Zovirax, acyclovir sodium
Drug Class
Antiviral (Herpesvirus Nucleoside Analog DNA Polymerase Inhibitor)

What is acyclovir?What is acyclovir?

What is acyclovir?

Acyclovir is an antiviral prescription medicine approved by the U.S. Food and Drug Administration (FDA) to:

Acyclovir is approved in different formulations and strengths for use in specific populations, including in people who are immunocompromised.

HSV and VZV infections can be opportunistic infections (OIs) of HIV. An OI is an infection that occurs more frequently or is more severe in people with weakened immune systems—such as people with HIV—than in people with healthy immune systems. To learn more about OIs, read the HIVinfo What is an Opportunistic Infection? fact sheet.

How is acyclovir used in people with HIV?How is acyclovir used in people with HIV?

How is acyclovir used in people with HIV?

The Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents With HIV and/or the Guidelines for the Prevention and Treatment of Opportunistic Infections in Children With and Exposed to HIV include recommendations on the uses of acyclovir in people with HIV to:

Treat

Prevent

  • Cold sores and genital lesions caused by HSV from recurring
  • Chicken pox from occurring in certain people who come in contact with someone who has active shingles or chicken pox

The recommended uses may not always be consistent with FDA-approved uses of acyclovir. See the Adult and Pediatric Opportunistic Infection Guidelines for complete information on recommended uses of acyclovir in adults and children with HIV. Acyclovir may have other recommended uses not listed above.

What should I tell my health care provider before using acyclovir?What should I tell my health care provider before using acyclovir?

What should I tell my health care provider before using acyclovir?

Before using acyclovir, tell your health care provider:

  • If you are allergic to acyclovir, valacyclovir, or any other medicines.
  • About any medical conditions you have or have had, especially:
    • Liver or kidney problems, including if you are receiving dialysis
    • Neurologic problems
    • Electrolyte imbalances
    • Dehydration
    • Weakened immune system (immunocompromised)
  • About anything that could affect your ability to take medicines, such as difficulty swallowing pills, difficulty remembering to take pills, or any health conditions that may prevent your use of intravenous medicines.
  • If you are pregnant or plan to become pregnant. Talk to your health care provider about the risks and benefits of using acyclovir during pregnancy. The Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents With HIV may include other recommendations on the use of acyclovir during pregnancy. Please refer to these guidelines for additional information.
  • If you are breastfeeding or plan to breastfeed. For mothers with HIV in the United States, the Guideline recommends speaking with your health care provider to discuss options for feeding your baby. Mothers with suppressed viral load have a less than 1% chance of transmitting HIV to their baby via their own milk. Although most medicines are safe to use while breastfeeding, some medicines should be avoided. Always let your health care provider know about all the medicines and supplements you are using before you start breastfeeding.
  • About other prescription and nonprescription medicines, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Acyclovir may affect the way other medicines or products work, and other medicines or products may affect how acyclovir works. Ask your health care provider if there are interactions between acyclovir and the other medicines you take.

How should I use acyclovir?How should I use acyclovir?

How should I use acyclovir?

Use acyclovir according to your health care provider’s instructions. Your health care provider will tell you how much acyclovir to use and when to use it. Before you start acyclovir and each time you get a refill, read any printed information that comes with your medicine.

What side effects can acyclovir cause?What side effects can acyclovir cause?

What side effects can acyclovir cause?

Acyclovir may cause side effects that can be mild or serious. To learn about possible side effects of acyclovir, see the FDA drug labels for acyclovir capsule, injection (solution), suspension, and tablet. or talk to your health care provider or pharmacist. Tell your health care professional if you have any side effect that bothers you or that does not go away. Your health care professional may be able to tell you about ways to prevent or reduce some side effects.

You may report side effects to FDA at 1-800-FDA-1088 (1-800-332-1088) or online.

How should acyclovir be stored?How should acyclovir be stored?

How should acyclovir be stored?

  • Store acyclovir capsules at room temperature, 68°F to 77°F (20°C to 25°C), and protect them from moisture.
  • Store vials of acyclovir injection at room temperature, 68°F to 77°F (20°C to 25°C).
  • Store acyclovir suspension at 59°F to 77°F (15°C to 25°C), and protect it from light.
  • Store acyclovir tablets at 59°F to 77°F (15°C to 25°C), and protect them from moisture and light.
  • Keep acyclovir in the container that it came in and keep the container tightly closed.
  • Do not use acyclovir if the original seal over the container opening is broken or missing.
  • Throw away acyclovir that is no longer needed or expired (out of date). Follow FDA guidelines on how to safely dispose of unused medicine. For information on disposing of needles and other sharps, please refer to these guidelines or ask your health care provider or pharmacist.
  • Keep acyclovir and all medicines out of reach of children.

Where can I find more information about acyclovir?Where can I find more information about acyclovir?

Where can I find more information about acyclovir?

Last Reviewed: June 12, 2025