Acyclovir (Topical)

Topical acyclovir (also known as aciclovir) is a common antiviral drug employed to treat infections caused by the herpes virus.


Acyclovir is an antiviral drug. It can slow or even stall the spread of the herpes virus in the body, but it cannot cure it. Sold under the names Zovirax and Sitavig, acyclovir can be delivered topically to the infected areas of the skin. Used in this way, it is effective in stalling the progress of the herpes simplex virus (genital warts), as well as herpes simplex labialis (cold sores).

Acyclovir can be applied topically as a cream or ointment. Zovirax Ointment and Zovirax Cream are the two most common forms of topical acyclovir. Treatments are typically broken up over multiple doses spanning the course of a day. Topical acyclovir is typically prescribed for about a week.

In a study published in volume 34, issue 7 of Clinical Infectious Diseases, acyclovir was demonstrated to cause broad 50% reductions in herpes simplex infections when compared to the control group. The acyclovir group suffered half the infectious episodes, the episodes were shorter, and the duration of the lesions was reduced by a third. Additionally, the period of viral shedding (the cannibalization of healthy cells to create viral progeny) was reduced by almost half. The study, however, was done on orally administered acyclovir, not topically administered acyclovir.

Other studies have measured the effects of acyclovir ointment on initial infection genital herpes. These studies demonstrated a remarkable decrease in the healing time for infectious outbreaks. Additionally, some patients reported a decrease in the duration of viral shedding and in the duration of pain.

Studies of recurrent genital herpes and herpes labialis, however, showed that acyclovir ointment only caused a brief reduction in the period of viral shedding.

Conditions treated include

Type of medicine

  • Topical antiviral


Patients should follow the dosing directions given to them by their doctor.

A glove or other barrier surface should be used to apply acyclovir ointment. Not doing so runs the risk of spreading the infection to other parts of your body. To apply both acyclovir cream and ointment, the patient should wash their hands before and after applying the medication.

Additionally, the patient should ensure that the area they intend to apply either acyclovir cream or acyclovir ointment to is clean and dry.

Acyclovir cream should be applied directly to the infected areas of skin as soon as symptoms begin. Acyclovir cream should be applied 5 times a day for 4 days. Patients should use the acyclovir cream for the full period prescribed, even if the infection subsides/goes away.

Children 12 years and older usually use an adult dose of acyclovir.

Acyclovir ointment should be applied in a sufficient quantity to cover the entire lesioned area every three hours, as many as 6 or 7 times daily. As with Acyclovir cream, treatment should begin as soon as symptoms develop. Patients should use the acyclovir ointment for the full period prescribed, even if the infection subsides/goes away.

The patient's symptoms should improve over the course of their acyclovir treatment. If the infection remains persistent, or worsens, the patient should contact their doctor immediately.

The dosages above are standard dosages, and typically do not need to be adjusted to account for age or weight. The direct application to the infected area, as opposed to deployment en masse into the body, removes the need for size related adjustments.

Patients should avoid using any other skin products in the area they are applying acyclovir cream or ointment to. Both genital herpes and herpes simplex labialis infections are best served by remaining dry.

Zovirax Cream, the brand name under which acyclovir cream is sold, is designed to combat herpes simplex labialis (better known as cold sores). Acyclovir cream features a 5% concentration; 1 gram of Zovirax Cream has 50 mg of acyclovir in it.

Zovirax Ointment, the brand under which acyclovir ointment is sold, is designed to combat genital herpes. It has a concentration of 5% acyclovir. Each gram of Zovirax Ointment has 50 mg of acyclovir.

Acyclovir cream should not be applied to genital herpes. Likewise, acyclovir ointment should not be applied to cold sores.

If a patient misses a dose, they should apply it as soon as they remember. However, if it is nearly time for the next dose, the patient should forego the dose they forgot and proceed as though they had applied it. Patients should not double up on applications in an attempt to retroactively apply a dose.

Side effects

Topical acyclovir in general has been well tolerated by patients. Relatively few have reported experiencing any side effects, and cases of serious side effects are rare. The body can tolerate many doses when taken intravenously or orally. As a result, when acyclovir is applied to the skin, its side effects are minimal.

Acyclovir, when applied topically, produces the majority of its side effects on the skin it has been applied to. Itching, hives, and rashes are all possible side effects, as well as pain, burning, or stinging sensations at the time of application.

In less common cases, pruritus and erythema multiforme can occur. Patients may also experience a stinging or burning sensation shortly after applying acyclovir cream or acyclovir ointment to their infections. Additionally, the skin around the area of application may begin to dry out and flake.

In rare cases, acyclovir can cause the blood vessels to widen, causing a flushing of the skin. Additionally, the skin could react negatively to the Zovirax Ointment or the Zovirax Cream, causing allergic contact dermatitis or eczema on the application area.

Toxic Epidermal Necrolysis and Stevens-Johnson Syndrome have occurred as a result of acyclovir. Patients should contact their doctor immediately if they begin to experience a red or purple rash, shedding of the skin, or sores in the mouth, nose, eyes, or genitals.

This is not necessarily a complete list of side effects. You can report side effects to the FDA at 1-800-FDA-1088.


Drugs to not affect the body in a vacuum. Different drugs can have different (or no effect) on each other, causing the drugs to have different, stronger, or weaker effects than originally intended. Because of this, it is imperative that patients provide their doctors with a full list of medications, supplements, and other drugs they are currently taking before taking acyclovir.

Topical acyclovir has been known to consistently react negatively to foscarnet, an antiviral. Patients are encouraged to avoid taking acyclovir and foscarnet together, and pay special attention to dosing if it is deemed necessary. Patients should consult with a doctor before beginning to take either medication.

Topical acyclovir may react negatively with the following medications, causing an increased risk of side effects, and causing an increased risk of severe side effects. Patients should use caution when considering taking the following medications and consult with a doctor before doing so.

  • Fosphenytoin
  • Phenytoin
  • Mycophenolate Mofetil
  • Mycophenolic Acid
  • Valproic Acid

Topical Acyclovir has been known to react negatively with talimogene laherparepvec, a drug used to treat inoperable skin cancer (talimogene laherparepvec itself is the herpes simplex virus). By taking acyclovir, you could limit the effectiveness of talimogene laherparepvec. Patients taking talimogene laherparepvec or with skin cancer should talk to their doctor before using any kind of acyclovir.


Topical acyclovir is prescription only, but not a controlled substance.

Acyclovir is a class B pregnancy drug. There is no proven pregnancy risk in humans. However, manufacturers encourage caution for use in pregnant women. Pregnant women should consult their doctor before using acyclovir.

Acyclovir absorbs in very small doses through the skin. Because of this, topical acyclovir is usually safe for breastfeeding women. However, acyclovir is excreted in breast milk, so women should consult their doctor before making that decision.

Acyclovir has not been evaluated in any child under twelve. Because of this, we cannot be certain of the risks involved with using topical acyclovir to treat the herpes virus in young children.

As with any drug, there is the possibility that a patient is allergic to acyclovir. Patients who experience symptoms of an allergic reaction, such as hives, have difficulty breathing, or experience swelling of the face, lips, tongue or throat should stop using acyclovir and contact their doctor immediately.

Hypersensitivity to acyclovir as well as other ingredients in acyclovir cream and acyclovir ointment have been reported, although they are quite rare. Patients who are hypersensitive to the drug can experience angioedema (swelling underneath the skin) and anaphylaxis, among other possible reactions. Patients who experience these symptoms should contact their doctor right away.

Topical acyclovir, in both its Zovirax Cream and Zovirax Ointment forms, is intended solely for external use. Patients should never intentionally ingest this product.

Topical acyclovir, in both its Zovirax Cream and Zovirax Ointment forms can be an eye irritant. Patients should take care to keep the medication away from their eyes. Because of this, patients should not attempt to use either product to combat a herpes simplex infection in their eyes.

Patients with a weakened immune system (can be caused by HIV, chemotherapy, etc.) should consult with their doctor before using topical acyclovir.

Genital herpes, caused by herpes simplex and treated by topical acyclovir, is a highly contagious, sexually transmitted disease. Patients suffering from a breakout in genital herpes should abstain from having sex, as no form of acyclovir, including topical forms, can prevent transmission.

Acyclovir overdose is rare, and almost unheard of when applied topically. Nevertheless, patients should be aware that overdose can occur, and symptoms of an overdose can include convulsions, lethargy, agitation, renal failure, and coma.

If a patient or anyone else has the misfortune to swallow topical acyclovir, they should call poison control at 1-800-222-1222. If the patient has collapsed or is not moving, emergency services should be contacted by calling 911.

Acyclovir will not cure herpes, in any form. It is nothing more than a tool to manage and limit potential breakouts of the virus.

Studies have not been performed to determine whether or not acyclovir is carcinogenic when applied topically. There are no instances of cancer being linked to acyclovir.


Patients are recommended to store the cream version of their acyclovir in a closed container at a temperature of 59 to 86 degrees Fahrenheit.

Patients are recommended to store the ointment version of their acyclovir in a closed container at a temperature between 59 and 77 degrees Fahrenheit.


Topical acyclovir is a powerful tool to contain herpes outbreaks, both in the form of genital herpes and cold sores. When compared to oral and intravenous forms of acyclovir, topical acyclovir is safer. Because so much less acyclovir makes it into the bloodstream it's much less taxing on the kidneys, and has a far smaller catalogue of side effects. The list of medications topical acyclovir interacts is short, especially when compared to the myriad of interactions oral and intravenous acyclovir can cause.

Because of its low impact delivery, topical acyclovir constitutes a very forgiving method of containing herpes outbreaks. It's a trade-off, though, that comes at the expense of effectiveness; topical acyclovir can lack the strength necessary to deal with more stubborn infections, and lacks the versatility that comes with the oral and intravenous routes.

Last Reviewed:
December 10, 2017
Last Updated:
April 04, 2018
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