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AIDSinfo Drug Database

AIDSinfo Drug Database

Drugs by class



Acyclovir  Audio icon

Other Names: acyclovir sodium, Zovirax
Drug Class: Opportunistic Infections and Coinfections
Chemical Images:
Click image to enlarge
Molecular Weight: 225.2069
acyclovir sodium
acyclovir sodium
Molecular Weight: 247.189

What is acyclovir?

Acyclovir is an antiviral prescription medicine approved by the U.S. Food and Drug Administration (FDA) for the treatment and prevention of herpes simplex virus (HSV) infections (including genital herpes) and for the treatment of varicella zoster virus (VZV) diseases (including shingles and chicken pox). The different formulations of acyclovir are approved for different uses and for specific populations.

HSV and VZV infections are opportunistic infections. An opportunistic infection is an infection that occurs more frequently or is more severe in people with weakened immune systems—such as those infected with HIV—than in people with healthy immune systems.

Acyclovir can also be used “off-label” to prevent certain VZV infections from occurring. “Off-label” use refers to use of an FDA-approved medicine in a manner different from that described on the medicine label. Good medical practice and the best interests of a patient sometimes require that a medicine be used “off-label.”

What HIV-related opportunistic infections is acyclovir used for?

The Guidelines for the Prevention and Treatment of Opportunistic Infections in HIV-Infected Adults and Adolescents, prepared by the Centers for Disease Control and Prevention (CDC), the National Institutes of Health (NIH), and the HIV Medicine Association of the Infectious Diseases Society of America (IDSA-HIVMA), includes recommendations on the HIV-related uses of acyclovir to:

  • Prevent:
    • Orolabial lesions (cold sores) and genital lesions caused by HSV infection from recurring (called secondary prophylaxis or maintenance therapy).
    • VZV infections, including shingles (also known as herpes zoster) and chicken pox (also known as primary varicella infection), from occurring in certain people who come in contact with someone who has active shingles or chicken pox. (This is called post-exposure prophylaxis and is an “off-label” use.)
  • Treat
    • HSV infections, including orolabial lesions and genital lesions.
    • VZV infections, including shingles and chicken pox.

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, for example, diabetes or liver problems.
  • About anything that could affect your ability to take medicines, such as difficulty swallowing or remembering to take pills.
  • 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.
  • If you are breastfeeding or plan to breastfeed. Do not breastfeed if you are infected with HIV.
  • About other prescription and nonprescription medicines, vitamins, nutritional supplements, and herbal products you are taking or plan to take. 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?

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?

  • Store acyclovir capsules, suspension, and tablets at 59°F to 77°F (15°C to 25°C) and protect from moisture.
  • Store acyclovir injection (powder, for solution) at room temperature, 68°F to 77°F (20°C to 25°C).
  • Safely throw away acyclovir that is no longer needed or expired (out of date).
  • Keep acyclovir and all medicines out of reach of children.

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, suspension, tablet; Injection (powder, for solution).

Last Reviewed: May 7, 2013

Last Updated: January 21, 2015

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