Acyclovir is a medicine used to treat infections caused by certain viruses. The drug is prescribed to improve symptoms and speed healing in people who have chickenpox, shingles, oral herpes, or genital herpes.

Acyclovir is also sometimes used to prevent outbreaks of genital herpes in individuals who are infected with the virus.

This drug is sold under different brand names. The brand Sitavig is only used to treat cold sores on the lips (not the genital area).

Acyclovir is an antiviral drug. It works by slowing the growth and spread of the herpes virus in the body.

This medicine won’t cure herpes, but it could improve symptoms.

The U.S. Food and Drug Administration (FDA) approved acyclovir in 2002.

uses

What is Acyclovir (Zovirax) used for?

Herpes Simplex -- Mucocutaneous/Immunocompetent Host
Herpes Simplex -- Mucocutaneous/Immunocompromised Host
Herpes Simplex Encephalitis
Herpes Zoster
Varicella-Zoster
Herpes Zoster -- Prophylaxis
Varicella-Zoster -- Prophylaxis
Infection - Bacterial/Fungal/Protozoal/Viral
Herpes Zoster Iridocyclitis
Herpes Zoster Peripheral Neuropathy
Herpes Zoster Meningitis
Varicella Pneumonitis
Herpes Zoster Otitis Externa
Herpes Simplex Labialis
Herpes Simplex -- Suppression
Herpes Zoster Myelitis
Herpes Simplex - Congenital

warnings

What is the most important information I should know about Acyclovir (Zovirax)?

You should not take this medicine if you are allergic to acyclovir or valacyclovir (Valtrex). You should not take acyclovir buccal tablets (Sitavig) if you are allergic to milk proteins.

Tell your doctor if you have ever had:

kidney disease; or
a weak immune system (caused by disease or by using certain medicine).

Tell your doctor if you are pregnant or breastfeeding.

Herpes can be passed to your baby during childbirth if you have a genital lesion when your baby is born. If you have genital herpes, it is very important to prevent herpes lesions during pregnancy. Take your medicine as directed to best control your infection.

It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.

Acyclovir should not be given to a child younger than 2 years old.

Side Effects

What are the side effects of Acyclovir (Zovirax)?

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

easy bruising or bleeding, purple or red pinpoint spots under your skin;
changes in behavior;
confusion, hallucinations; or
signs of a kidney problem--little or no urinating; painful or difficult urination; swelling in your feet or ankles; feeling tired or short of breath.

Common side effects may include:

mild skin pain;
rash, itching;
nausea, vomiting, diarrhea;
headache; or
mouth pain while using an acyclovir buccal tablet.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Pregnancy & Breastfeeding

Can I take Acyclovir (Zovirax) if I’m pregnant or breastfeeding?

No evidence of risk in humans

Based on FDA pregnancy categories

Tell your doctor if you are pregnant or breastfeeding.

It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.

Interactions

What drugs and food should I avoid while taking Acyclovir (Zovirax)?

Avoid brushing your teeth, chewing gum, or wearing an upper denture while you have a buccal tablet in your mouth. You may rinse your mouth gently. Drink plenty of liquids to prevent dry mouth.

Herpes infections are contagious and you can infect other people, even while you are being treated with acyclovir. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.

Taking this medicine will not prevent you from passing genital herpes to your sexual partner. Avoid sexual intercourse while you have active lesions or the first symptoms of an outbreak. Genital herpes may still be contagious through "viral shedding" from your skin, even if you have no symptoms.

Dosage Guidelines & Tips

How to take Acyclovir (Zovirax)?

Use Acyclovir (Zovirax) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Start taking acyclovir as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters). Start taking Sitavig within 1 hour after you first notice sold core symptoms, before the cold sore appears.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you do not understand these instructions.

Do not crush, chew, suck on, or swallow a buccal tablet. Place the flat side of the tablet against your upper gum, on the same side of the mouth as your cold sore. Allow the tablet to dissolve in your mouth throughout the day. You may eat and drink normally while the buccal tablet is in place.

Do not give an acyclovir buccal tablet to a young child or choking could occur.

Shake the oral suspension (liquid) before you measure a dose. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Acyclovir doses are based on weight (especially in children and teenagers). Your dose needs may change if you gain or lose weight.

Drink plenty of water while you are taking acyclovir to keep your kidneys working properly.

Use this medicine for the full prescribed length of time, even if your symptoms quickly improve. Skipping doses may increase the risk of your virus becoming resistant to medication.

Lesions caused by herpes viruses should be kept as clean and dry as possible. Wearing loose clothing may help to prevent irritation of the lesions.

Store at room temperature away from moisture and heat.

What should I do if I missed a dose of Acyclovir (Zovirax)?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.