Zovirax (acyclovir) is an antiviral drug. It slows the growth and spread of the herpes virus in the body. Acyclovir will not cure herpes, but it can lessen the symptoms of the infection.

Zovirax is used to treat infections caused by herpes viruses, such as genital herpes, cold sores, shingles, and chicken pox.

Zovirax may also be used for purposes not listed in this medication guide.

Take Zovirax exactly as it was prescribed for you. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Treatment with Zovirax should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).

Tell your doctor if you have any changes in weight. Zovirax doses are based on weight (especially in children and teenagers), and any changes may affect the dose.

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

Use this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely treated. Zovirax will not treat a viral infection such as the flu or a common cold.

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.

Take Zovirax for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated.

Treatment with Zovirax should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).

Herpes infections are contagious and you can infect other people, even while you are being treated with Zovirax. 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.

Zovirax is not expected to harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

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.

Acyclovir passes into breast milk and may harm a nursing infant. Do not take this medication without telling your doctor if you are breast-feeding a baby.

Herpes infections are contagious and you can infect other people, even while you are being treated with Zovirax. 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.

Nausea, diarrhea, headache, or vomiting may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if any of these unlikely but serious side effects occur: dizziness, drowsiness, signs of kidney problems (such as a change in the amount of urine, unusual back/side pain), mental/mood changes (such as agitation, confusion, hallucinations), shaky/unsteady movement, trouble speaking.

This medication may rarely cause a life-threatening disorder that affects the blood cells, kidneys, and other parts of the body. This disorder is more likely to occur if you have conditions related to a weakened immune system (such as HIV disease, bone marrow transplant, kidney transplant). Seek immediate medical attention if any of these rare but serious side effects occur: extreme tiredness, slow/fast/irregular heartbeat, easy bruising/bleeding, new fever, bloody/dark urine, severe stomach/abdominal pain, yellowing eyes/skin, sudden vision changes, loss of consciousness, seizures.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

How should I use this medicine?

Take this medicine by mouth with a glass of water. Follow the directions on the prescription label. You can take it with or without food. Take your medicine at regular intervals. Do not take your medicine more often than directed. Take all of your medicine as directed even if you think your are better. Do not skip doses or stop your medicine early.

Talk to your pediatrician regarding the use of this medicine in children. While this drug may be prescribed for selected conditions, precautions do apply.

What if I miss a dose?

If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

What may interact with this medicine?

Probenecid may interact with Zovirax.

What should I watch for while using this medicine?

Tell your doctor or health care professional if your symptoms do not improve. This medicine works best when started very early in the course of an infection. Begin treatment at the first signs of infection.

Drink 6 to 8 glasses of water or fluids every day while you are taking this medicine. This will help prevent side effects.

You can still pass chickenpox, shingles, or herpes to another person even while you are taking this medicine. Avoid contact with others as directed. Genital herpes is a sexually transmitted disease. Talk to your doctor about how to stop the spread of infection.