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Foscarnet Sodium  Audio icon

Other Names: Foscavir
Drug Class: Opportunistic Infections and Coinfections
Chemical Image:
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foscarnet sodium
foscarnet sodium
Molecular Weight: 300.0388

What is foscarnet sodium?


Foscarnet sodium is a prescription medicine approved by the U.S. Food and Drug Administration (FDA) for the treatment of cytomegalovirus retinitis (a viral infection and inflammation of the eye’s retina) in individuals with AIDS. Foscarnet sodium is also FDA-approved for the treatment of a certain type of herpes simplex virus (HSV) infection—called mucocutaneous acyclovir-resistant HSV infection—in immunocompromised individuals.

Cytomegalovirus (CMV) diseases—such as those affecting the eye (retinitis), esophagus (esophagitis), or colon (colitis)—and HSV diseases 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.

Foscarnet sodium can also be used “off-label” to prevent and treat other opportunistic infections of HIV infection. “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 foscarnet sodium 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 foscarnet sodium to:

  • Prevent:
    • CMV retinitis from recurring (called secondary prophylaxis or maintenance therapy). (This is an “off-label” use.)
  • Treat:
    • CMV retinitis.
    • Other types of CMV disease, including CMV pneumonitis (infection and inflammation of the lungs) and CMV neurological disease (infection and disease of the nervous system). (This is an “off-label” use.)
    • Acyclovir-resistant mucocutaneous HSV infection.  
    • Certain types of varicella-zoster virus (VZV) disease, including progressive outer retinal necrosis (an infection and inflammation of the eye’s retina) and VZV infections that are resistant to treatment with the drug acyclovir. (This is an “off-label” use.)


What should I tell my health care provider before taking foscarnet sodium?


Before taking foscarnet sodium, tell your health care provider:

  • If you are allergic to foscarnet sodium 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 foscarnet sodium can harm an unborn baby is unknown. Foscarnet sodium should be used during pregnancy only if clearly needed.
  • 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 foscarnet sodium and the other medicines you take.

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


How should I take foscarnet sodium?


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


How should foscarnet sodium be stored?


  • Store foscarnet sodium injection at room temperature, 68°F to 77°F (20°C to 25°C), and protect it from excessive heat and from freezing.
  • Safely throw away foscarnet sodium that is no longer needed or expired (out of date).
  • Keep foscarnet sodium and all medicines out of reach of children.


Where can I find more information about foscarnet sodium?


More information about foscarnet sodium is available:


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


Last Reviewed: May 7, 2013

Last Updated: May 7, 2013