Penciclovir (Topical)

As an antiviral, Penciclovir is topically applicated to cold sores in order to treat viral infections and outbreaks of the herpes simplex virus as well as related viral strains.


Penciclovir is marketed under the brand name Denavir and is a part of a larger family of medications that are used for antiviral purposes. Antivirals are usually used to treat infections related to one specific type or group of a virus, and Penciclovir is intended to combat the Herpes Simplex virus. When it is topically applied, it is intended to be applied directly to the infected area around the mouth. Most commonly, this means direct applications to cold sores for the purpose of relieving the pain of the sores and to aid in healing. However, it is important to note that this antiviral treatment is not a cure for cold sores or the herpes simplex virus but rather a treatment for that particular outbreak. This is a potent topical medication that is only available by prescription and is only provided in the form of a cream.

Condition Treated

  • Herpes

Type Of Medicine

  • Antiviral

Side Effects

As with most medications, there is a certain risk of side effects. The most common and serious side effect is associated with an allergic reaction and may be serious enough to merit medical attention. A patient using this topical treatment should contact their doctor if they break out in hives, experience difficulty breathing, or have swelling or redness on their face or mouth area to include the tongue and throat. This serious side effect can result in profound pain, itching, and irritation of the application area and emergency medical services should be contacted if these symptoms emerge rapidly or worsen with time.

While some medications are known to produce significant side effects, Penciclovir has a very low risk of potentially unwanted effects. However, everyone is different and if an unwanted reaction to the medication is detected it should be immediately reported to the prescribing physician as this may indicate an allergic reaction or a more serious medical condition. Those who are using Penciclovir for the treatment of cold sores should check with their doctor if they notice any increase in pain after application or if the medication stings excessively when applied.

In addition to the rare allergic reactions, there are some more common side effects that are considered temporary in nature and tend to subside as the body adjusts to the topical medication. Some patients have experienced headaches when they first start taking the medication. A less common side effect is a change in the sense of taste or a feeling of numbness at the application area after using Penciclovir for the first time. Redness of the skin or a rash may occur briefly when getting used to the topical medication, but if it persists for more than a few days then medical attention should be sought out for the condition.


When using Penciclovir to treat herpes it should only be applied to the lips or parts of the face directly infected and breaking out with sores. It will have the best effect if it is used as soon as possible after an infection manifests. If cold sores are allowed to fully break out they may take longer to heal even with the medication. Medication is for topical use only and should be kept away from the eyes, inside of the mouth or nose, and is not to be ingested in any way.

The topical cream should be applied to the affected area every two hours during waking hours for four days. While it is uncommon to use it for children, when it is used for them the use must be as prescribed by a pediatric specialist. If a dose is missed the patient should skip to the next dose in the regular interval as there is a certain risk of overdose when double dosing. With so many doses applied throughout the day one missed dose is not expected to have a detrimental effect.


Penciclovir has a relatively low risk of interactions with other medications. There is not much likelihood that the vast majority of orally administered or injected medications will have a reaction with topically applied antivirals such as penciclovir. However, certain medications should not be used together and patients using this topical treatment need to keep their doctor fully appraised of any and all prescription and non-prescription medication that is being used while they are treating their cold sores with Penciclovir. This also applies to other remedies such as herbal supplements or vitamins.

While there are no known interactions with other products such as food or drink, alcohol or tobacco use should be discussed with a physician before using this medication. Patients who may have problems with their immune systems may have unintended results when using this antiviral medication and it is unknown if it will work properly. Those with a suppressed immune system should use Penciclovir with caution.


The decision to use Penciclovir for treating herpes simplex infections should be carefully weighed by a prescribing physician. While there are relatively few risks associated with the use of this topical treatment, certain precautions should be taken to review past allergic reactions or test patients for allergies prior to applying the cream as the allergic reaction is the most serious side-effect of using this medication. There is not a sufficient amount of data concerning how Penciclovir effects children, the elderly, or pregnant or nursing mothers. It is not known if the Penciclovir will function exactly as it is supposed to for these vulnerable groups, so this needs to be taken into consideration when prescribing this remedy for the treatment of herpes.

There is a certain risk of overdose associated with Penciclovir, but an overdose that is applied topically is not considered serious. However, if the medication has been swallowed it should be treated as a poisoning event and immediate emergency medical attention will be necessary. If the medication gets in a patient's eye than it should quickly be rinsed out with water as failure to do this can result in damage to the eye as well as extreme distress. It is also important to note that this topical treatment is not considered a safe or effective treatment for genital herpes and misuse of this medication can result in unwanted complications.


As a topical cream, care should be taken in the storage of Penciclovir to ensure that it works as it is intended to. It should be stored at room temperature away from sources of heat or moisture, so storing it in the bathroom is out of the question. It should also be stored in as secure a space as possible and out of the reach of children or family pets. It can do serious harm if ingested and the container it comes in is unlikely to be child-resistant. If the medication is equipped with a safety cap it should be securely locked in place when not in use. It is not recommended to keep the cream in any container other than the original container it comes in when prescribed. It is not recommended that this medication be refrigerated, frozen, or kept outdoors or in a glove compartment as extreme temperatures can degrade the medication and make it ineffective for the treatment of herpes.

If the medication is no longer needed or it has expired it should not be maintained in the home. Rather, it should be disposed of in accordance with guidelines for the disposal of medical waste in the local area. Patients are cautioned not to dispose of Penciclovir with regular garbage or flush it down the toilet as this can harm animals or the environment. If the prescribing physician provides direction regarding disposal or if there is a medical return or take-back program, these resources should be contacted for further instructions.


Penciclovir is typically prescribed to patients who are aware of their herpes infection and have had little success treating chronic cold sores with other means. It is fast-acting when applied and can demonstrate significant healing in as little as a week. When it is used as directed, Penciclovir can provide significant relief for patients who are suffering from the cold sores caused by the herpes simplex virus. While topical antiviral treatment may not be appropriate for all patients, it demonstrates a very low risk when used properly and can help sores heal in a short amount of time. So long as the patient understands that this is a treatment for an acute infection and not a cure for the persistent virus, topical treatments of Penciclovir can be a useful component of a comprehensive treatment plan for those who are afflicted with cold sores on a regular basis.