Drug information

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 treat and prevent the reoccurrence of herpes simplex virus (HSV) episodes (including genital herpes) and to treat varicella zoster virus (VZV) diseases (including chicken pox and shingles). Acyclovir is approved in different formulations and strengths for use in specific populations, including in people who are immunocompromised.

HSV and VZV infections are 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 Clinical Info 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 HIV-Infected Adults and Adolescents include recommendations on the uses of acyclovir in people with HIV.

Using a medicine as indicated on the medicine label is called on-label use; using the medicine in a different way is called off-label use. Off-label use, for example, can include using a drug for a different disease or medical condition. Good medical practice and the best interests of a patient sometimes require that a medicine be used off-label.

The guidelines include recommendations on the following uses of acyclovir:

On-label uses:

  • Treat:
    • HSV episodes, including orolabial lesions (cold sores) and genital lesions
    • VZV disease, including chicken pox and shingles
  • Prevent orolabial lesions and genital lesions caused by HSV infection from reoccurring

Off-label uses:

  • Treat acute retinal necrosis, which is an inflammatory condition that can damage or destroy the retina of the eye.
  • Prevent chicken pox in people with HIV who are at risk of infection from close contact with a person who has active chicken pox or shingles (both chicken pox and shingles are VZV diseases). This is called post-exposure prophylaxis.

The above list may not include all of the HIV-related uses of acyclovir recommended in the guidelines. Some recommended uses, such as uses in certain rare circumstances, may have been omitted.

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

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


Before taking acyclovir, tell your health care provider:

  • If you are allergic to acyclovir or any other medicines.
  • About any medical conditions you have or have had.
  • About anything that could affect your ability to take medicines, such as difficulty swallowing pills, difficulty remembering to take a scheduled dose, or any health conditions that may prevent your use of intravenous medicines.
  • If you are pregnant or plan to become pregnant. Whether acyclovir can harm an unborn baby is unknown. Acyclovir should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Talk to your health care provider about possible risks with taking acyclovir when pregnant.
  • If you are breastfeeding or plan to breastfeed. Do not breastfeed if you have HIV.
  • 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.

Ask your health care provider about possible side effects from acyclovir. Your health care provider will tell you what to do if you have side effects.

How should I take acyclovir?How should I take acyclovir?

How should I take acyclovir?


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

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

How should acyclovir be stored?


  • Store acyclovir tablets at 59°F to 77°F (15°C to 25°C) and protect them from moisture and light.
  • Store acyclovir suspension at 59°F to 77°F (15°C to 25°C) and protect it from light.
  • Store acyclovir capsules at room temperature, 68°F to 77°F (20°C to 25°C), and protect them from moisture.
  • Store acyclovir injection for intravenous infusion at room temperature, 68°F to 77°F (20°C to 25°C).
  • 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.
  • 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?


More information about acyclovir is available:

The above Patient Version drug summary is based on the following FDA label(s): Capsule; Injection (solution); Suspension; Tablet.


Last Reviewed: May 3, 2019