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What is foscarnet?

Foscarnet (also called Foscavir®) is a medicine used to treat viral infections caused by cytomegalovirus (also called CMV) and other viruses. It is available as a clear liquid given into a vein (IV) over a period of one (1) to 2 hours.

Possible side effects of foscarnet


  • Nausea, vomiting
  • Fever
  • Headache

Later (more than a day after treatment starts)

  • Decreased kidney function
  • Changes in electrolyte levels
  • Changes in liver function
  • Decreased calcium levels
  • Diarrhea

If you have any of these side effects, tell the doctor right away:

  • Seizures
  • Decrease in how much or how often you urinate
  • Numbness or tingling of the feet or hands
  • An allergic reaction including itching, trouble breathing, pain in the chest, blue skin color, or swelling of face, lips, tongue or throat

In case of a severe side effect or reaction, call the doctor, nurse, or pharmacist at 595-3300. If you are outside the Memphis area, dial toll-free 1-866-2STJUDE (1-866-278-5833), and press 0 once the call is connected.

Special instructions for foscarnet

  • Drinking plenty of liquids will reduce the chance of kidney damage while you are receiving foscarnet. The doctor or nurse will tell you how much liquid you should drink.
  • To help hydrate you, the staff will also give saline solution by vein (IV) before a foscarnet infusion.
  • Electrolyte supplements may be needed during therapy with foscarnet. Electrolytes can be given by mouth or given by vein in IV fluids.
  • While you are receiving foscarnet, blood tests will be done to check for changes in kidney or liver function and to monitor blood counts and electrolytes.
  • Foscarnet can cause birth defects. If you are sexually active, you should use 2 forms of birth control while you are receiving foscarnet and for 90 days after the foscarnet therapy ends.


This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

ATTENTION: If you speak another language, assistance services, free of charge, are available to you. Call 1-866-278-5833 (TTY: 1-901-595-1040).

ATENCIÓN: si habla español, tiene a su disposición servicios gratuitos de asistencia lingüística. Llame al 1-866-278-5833 (TTY: 1-901-595-1040).

تنبيه: إذا كنت تتحدث باللغة العربية فيمكنك الاستعانة بخدمات المساعدة اللغوية المتوفرة لك مجانا. .يرجى الاتصال بالرقم. 5833-278-866-1  (الهاتف النصي: 1040-595-901-1).