In the U.S.—

In Canada—

Other commonly used names are acyclovir; acycloguanosine.

• Antiviral, topical

Acyclovir (ay-SYE-kloe-veer) belongs to the family of medicines called antivirals. Antivirals are used to treat infections caused by viruses. Usually they work for only one kind or group of virus infections.

Topical acyclovir is used to treat the symptoms of herpes simplex virus infections of the skin, mucous membranes, and genitals (sex organs). Although topical acyclovir will not cure herpes simplex, it may help relieve the pain and discomfort and may help the sores (if any) heal faster. Topical acyclovir may also be used for other conditions as determined by your doctor.

Acyclovir is available only with your doctor's prescription, in the following dosage forms:

Topical
• Cream (Canada)
• Ointment (U.S. and Canada)

In deciding to use a medicine, the risks of using the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For acyclovir, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to acyclovir. Also tell your health care professional if you are allergic to any other substances, such as preservatives or dyes.

Pregnancy—Topical acyclovir has not been studied in pregnant women. However, this medicine has not been shown to cause birth defects or other problems in animal studies using mice, rats, or rabbits, except when given in very high doses in a study using rats.

Breast-feeding—It is not known whether topical acyclovir passes into the breast milk. However, acyclovir ointment has not been reported to cause problems in nursing babies, even though small amounts of topical acyclovir are absorbed through the mother's skin and mucous membranes. Although most medicines pass into breast milk in small amounts, many of them may be used safely while breast-feeding. Mothers who are taking this medicine and who wish to breast-feed should discuss this with their doctor, especially when lesions are present on or near the breast.

Children—Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of topical acyclovir in children with use in other age groups.

Older adults—Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults. Although there is no specific information comparing the use of topical acyclovir in the elderly with use in other age groups, this medicine is not expected to cause different side effects or problems in older people than it does in younger adults.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your health care professional if you are using any other topical prescription or nonprescription (over-the-counter [OTC]) medicine that is to be applied to the same area of the skin.

Acyclovir may come with patient information about herpes simplex infections. Read this information carefully. If you have any questions, check with your health care professional.

Do not use this medicine in the eyes.

Acyclovir is best used as soon as possible after the signs and symptoms of herpes infection (for example, pain, burning, or blisters) begin to appear.

Use a finger cot or rubber glove when applying this medicine. This will help keep you from spreading the infection to other areas of your body and will prevent the transmission of the infection to other persons . Apply enough medicine to completely cover all the sores (blisters). A 1.25-centimeter (approximately ½-inch) strip of ointment applied to each area of the affected skin measuring 5 × 5 centimeters (approximately 2 × 2 inches) is usually enough, unless otherwise directed by your doctor.

To help clear up your herpes infection, continue using acyclovir for the full time of treatment, even if your symptoms begin to clear up after a few days. Do not miss any doses. However, do not use this medicine more often or for a longer time than your doctor ordered.

Dosing—

The dose of topical acyclovir will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average dose of topical acyclovir. If your dose is different, do not change it unless your doctor tells you to do so.

• For topical dosage form (cream):
  • For herpes simplex infection:
    • Adults—Apply to the affected area(s), four to six times a day, for up to ten days.
    • Children—Use and dose must be determined by your doctor.
• For topical dosage form (ointment):
  • For herpes simplex infection:
    In the U.S.
    • Adults—Apply to the affected area(s), every three hours, for a total of six times a day, for seven days.
    • Children—Use and dose must be determined by your doctor.
    In Canada
    • Adults—Apply to the affected area(s), four to six times a day, for up to ten days.
    • Children—Use and dose must be determined by your doctor.

Missed dose—

If you miss a dose of this medicine, apply it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule.

Storage—

To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Keep the medicine from freezing.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

Women with genital herpes may be more likely to get cancer of the cervix (opening to the womb). Therefore, it is very important that Pap tests be taken at least once a year to check for cancer. Cervical cancer can be cured if found and treated early.

If your symptoms do not improve within 1 week, or if they become worse, check with your doctor.

Consider the possibility of viral resistance to acyclovir if little or no improvement in symptoms during therapy.

The areas affected by herpes should be kept as clean and dry as possible. Also, wear loose-fitting clothing to avoid irritating the sores (blisters).

Herpes infection of the genitals can be caught from or spread to your partner during any sexual activity. Although you may get herpes even though your sexual partner has no symptoms, the infection is more likely to be spread if sores are present. This is true until the sores are completely healed and the scabs have fallen off. The use of a condom (prophylactic) may help prevent the spread of herpes. However, spermicidal (sperm-killing) jelly or a diaphragm will not help prevent the spread of herpes. Therefore, it is best to avoid any sexual activity if either you or your partner has any symptoms of herpes. It is also important to remember that acyclovir will not keep you from spreading herpes to others.

Along with its needed effects, a medicine may cause some unwanted effects. The following side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of these effects continue or are bothersome:

• More common
  • Mild pain, burning, or stinging 
  
  

• Less common
  • Itching 
  
  

• Rare
  • Itching, stinging, or redness of the genital area;  skin rash 
  
  

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.