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What is acyclovir?

Acyclovir (also called Zoviraxâ) is a medicine used to treat viral infections. Acyclovir is available in the following forms:

  • 200 mg capsules taken by mouth
  • 400 mg and 800 mg tablets taken by mouth
  • A white 40 mg/mL liquid taken by mouth
  • A clear liquid given into a vein (IV)
  • An ointment that is applied to the skin

How to take and store acyclovir

  • This medicine may be taken with or without food. If upset stomach occurs, take acyclovir with food.
  • Store tablets and capsules at room temperature in a dry place.
  • Store oral liquid acyclovir at room temperature. Shake well before use. Use oral syringes provided by pharmacy to measure the dose of liquid.
  • The oral liquid can be used for patients who have feeding tubes. The feeding tube should be flushed before and after the medicine is given.
  • Store the ointment at room temperature. Apply ointment to the skin only; do not take by mouth.
  • Wash hands before and after using the ointment. Use gloves to apply a thin layer to the affected area and rub in gently.

Possible side effects of acyclovir

Note: Side effects that happen only when acyclovir is given IV or applied to the skin are indicated in parentheses below.


  • Rashes, hives, itching
  • Nausea
  • Drop in blood pressure, with dizziness or feeling “light-headed”
  • Burning and stinging of skin (ointment)
  • Swelling, pain, or redness at injection site (IV)

Later (more than a day after treatment starts)

  • Trembling
  • Feeling confused or drowsy
  • Changes in kidney function (IV)
  • Mouth sores
  • Changes in liver function
  • Diarrhea
  • Drop in white blood cell counts

These are the most common side effects, but there may be others. Please report all side effects to the doctor or nurse.

In case of a severe side effect or reaction, call the doctor, nurse, or pharmacist at 901-595-3300. 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.


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).

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.