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.
Important information
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.
Before taking this medicine
You should not take Zovirax if you are allergic to acyclovir or valacyclovir (Valtrex).
To make sure Zovirax is safe for you, tell your doctor if you have:
FDA pregnancy category B. Zovirax is not expected to harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.
See also: Pregnancy and breastfeeding warnings (in more detail)
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.
How should I take Zovirax?
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).
Shake the oral suspension (liquid) well just before you measure a dose. Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.
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.
What happens if I miss a dose?
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include agitation, seizure (convulsions), or loss of consciousness.
What should I avoid while taking Zovirax?
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.
Zovirax side effects
Get emergency medical help if you have any of these signs of an allergic reaction to Zovirax: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
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easy bruising or bleeding, purple or red pinpoint spots under your skin; or
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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 Zovirax side effects may include:
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nausea, vomiting;
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diarrhea;
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general ill feeling;
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headache; or
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.
See also: Side effects (in more detail)
What other drugs will affect Zovirax?
Zovirax can harm your kidneys. This effect is increased when you also use certain other medicines, including: probenecid, antivirals, chemotherapy, injected antibiotics, medicine for bowel disorders, medicine to prevent organ transplant rejection, injectable osteoporosis medication, and some pain or arthritis medicines (including aspirin, Tylenol, Advil, and Aleve).
Other drugs may interact with acyclovir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.
