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Penciclovir - Indication, Dosage, Precautions, and Pharmacological Aspects

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Penciclovir is a drug used to treat herpes labialis which is caused by herpes simplex virus (HSV). Read the article below to learn more.

Written by

Dr. Neha Rani

Medically reviewed by

Dr. Pandian. P

Published At November 15, 2023
Reviewed AtNovember 15, 2023

Drug Overview:

Adults with herpes labialis on their lips and faces are caused by the herpes simplex virus (HSV) and are treated with Penciclovir. Penciclovir lessens discomfort and itching when given as soon as the initial symptoms appear, but it does not treat herpes infections. The drug got approved in the year 1996.

For Patients:

What Is Herpes Labialis?

Herpes labialis or cold sores are red, fluid-filled blisters that occur on the face or close to the lips. They are caused by the herpes simplex virus (HSV), commonly HSV type 1. They occur in patches and could last for two weeks or more. Rarely, cold sores may develop on the lips, nose, or mouth.

What Are the Clinical Indications For Herpes Labialis?

Through intimate touch, such as kissing or direct skin-to-skin contact, these sores can spread from one person to another. It is crucial to remember that sores can spread even if they are not obvious or readily apparent. Herpes labialis can recur at any time, and there is no known treatment for them. Cold sores can be treated with some drugs, and they can also keep them from coming again.

What Are the Side Effects of Penciclovir?

The following side effects reported due to Penciclovir must be reported to the healthcare expert in case it does not subside:

  • Pain in the head.

  • Skin irritation is felt at the site of the application of the drug.

  • Redness, numbness, and burning sensation of the skin can be noticed.

Rarely does the drug cause a very severe allergic response. However, if someone displays any of the symptoms of a serious allergic reaction, such as a rash, itching, or swelling (especially of the face, tongue, or neck), severe dizziness, or trouble breathing, they should seek medical assistance right away.

How Is Medicine Stored and Disposed Of?

The medication needs to be stored in its original container and packaging. It needs to be tightly fastened and kept out of the children's reach. This act guarantees their security. Never keep or store medications in a bathroom due to high humidity levels. It should always be kept at an ideal room temperature for storage.

Additionally, medications should never be thrown out in the open or flushed down the toilet. Animals, including pets, may be at risk from this. A take-back program or disposal of medications in accordance with government regulations should always be used for disposal. People should speak with the pharmacist if they are still unclear.

What Specific Safety Measures Should Be Taken?

Prior to using Penciclovir, the patient must inform about the below-mentioned information to their doctors:

  • If the patient has an allergy to Acyclovir, Penciclovir, or any other drugs.

  • If the patient is taking any medicines and over-the-counter medicines.

  • If a patient using Penciclovir is expecting a child, intends to become pregnant, or is currently nursing a kid.

How Is Penciclovir Taken by the Patient?

Penciclovir is available as a cream. It is applied on the external surface of the body over the course of four days, and the time interval for each application is two hours. It is only applied when the patient is awake and is not applied during the time when they are sleeping. The patient should diligently follow the instructions on the prescription label and should not deviate from the instruction manual. If there are any questions about anything, contact the doctor, pharmacist, or other medical professionals. Use just enough cream to thoroughly cover all wounds and gently rub it in. Despite feeling well, the use of the medicine should not be advised until advised by the doctor. Never stop taking Penciclovir without consulting a doctor first.

How to Apply Topical Antiviral Cream Penciclovir?

Use this medicine as soon as an infection (such as tingling, burning, redness, or sores) manifests itself. Prior to and following the use of this medication, wash hands with soap and water. Prior to using the medicine, clean and dry the affected regions. The region of the cold sore or the area of tingling, itching, redness, or swelling should be thoroughly covered with Penciclovir cream, which the patient should then gently rub in. Apply the lotion as instructed by the doctor, typically every two hours (except while sleeping), for four days. Apply only on the skin. Since this drug might irritate the eyes, avoid applying it in or close to the eyes. If the medicine is in the eyes, thoroughly rinse them with water. Apply outside of the mouth and nose. The amount of medicine absorbed by the skin must be consistent for this treatment to function optimally. Use this medication at regular intervals. Utilize it at the same time each day so as to not miss the dose.


  • If a patient forgets to take a dosage of Penciclovir, they should take it as soon as they recall, making sure to take the rest of the day's doses at regular intervals. However, it is advised to skip the missed dosage and go on with the usual dosing plan if it is almost time for the next planned dose. It is crucial to avoid administering a second dose to make up for the missing one.

  • Herpes, or cold sores, may spread quickly. Herpes cannot be stopped from spreading using Penciclovir cream. When there is an outbreak, refrain from kissing or any close physical contact with people until the cold sores are totally cured. Additionally, try to avoid touching the cold sore. Upon touching, the hands should be washed immediately.

For Doctors:

What Are the Pharmacological Aspects of Penciclovir?

Physical Properties of the Drug:

  • Drug Group - Antiviral drug.

  • Appearance - White to pale yellow solid.

  • Chemical Name - 9-[4-hydroxy-3-(hydroxymethyl)butyl] guanine.

  • Empirical Formula - C10H15N5O3.

  • Molecular Weight - 253.26.

  • Solubility - 10.0 mg/mL (milligram per milliliter) at pH 2.

  • Components of the Drug - Cetostearyl alcohol, polyoxyl 20, mineral oil, propylene glycol, cetostearyl ether, white petrolatum, and purified water.

Mechanism of Action: The antiviral drug Penciclovir has inhibitory effects on HSV-1 and HSV-2, which are the two strains of the herpes simplex virus. The viral thymidine kinase phosphorylates Penciclovir and changes to a monophosphate form when cells are infected with HSV-1 or HSV-2. Cellular kinases then proceed to transform the monophosphate form into the active form, which is known as Penciclovir triphosphate.

Penciclovir triphosphate competes with deoxyguanosine triphosphate to suppress HSV polymerase, according to biochemical research. The selective suppression of herpes viral DNA synthesis and subsequent replication is caused by this inhibition. In cells cultivated with HSV-1 or HSV-2, Penciclovir triphosphate has an intracellular half-life of ten hours and 20 hours, respectively. The intracellular half-life's therapeutic relevance, however, is still unclear.


Drug Use in Specific Populations:

  • Pregnancy - There are no significant and reliable studies on expectant mothers regarding the use of Penciclovir. However, research work done on animals indicates that there are no adverse effects reported in them. Penciclovir should only be used during pregnancy if absolutely necessary, as research on animal reproduction is not necessarily indicative of human response. Doctors make the final decision for the patients.

  • Lactating Mother - No data are available about the topical use of Penciclovir and its excretion in breast milk. Penciclovir, however, was excreted in breast milk at levels greater than those reported in plasma after oral treatment of Famciclovir (the oral prodrug of Penciclovir) in lactating rats. Therefore, a choice should be implemented about drug discontinuation, taking into consideration the significance of the medicine to the mother. There is no information on the safety of Penciclovir in newborns.

  • Pediatric Population - According to an open-label, uncontrolled study, 102 individuals with recurrent herpes labialis, aged 12 to 17, were treated with Penciclovir cream 1 %. Adverse events that occurred were generally similar to those that were reported for adult patients. Pediatric patients younger than 12 years old have not been studied for safety and efficacy.

  • Geriatric Population - As per a study, the pattern of adverse events in 74 people under the age of 65 years was similar to that seen in younger patients.

What Are the Indications and Contraindications for Penciclovir?

  • Indications - It is approved to treat recurrent herpes labialis (cold sores) in adults and children who are 12 years and older.

  • Contraindication - Patients with known hypersensitivity to the drug or any of its ingredients should not use it.

Warnings and Precautions:

Cold sores on the lips and face caused by herpes labialis should only be treated with Penciclovir. It is not advised to apply it to human mucous membranes due to a lack of facts. Applying the drug in or close to the eyes should be avoided since it may irritate them. It is advised to get the lesions checked for a possible subsequent bacterial infection if they do not improve or get worse during therapy. It is unknown whether Penciclovir is effective in those with weakened immune systems.

What Are the Drug Interactions of Penciclovir?

Drug interactions may alter how a drug functions or raise the possibility of major adverse effects. A patient should keep a list of everything they use, including herbal items, prescriptions, and over-the-counter medications, and provide it to their doctor and pharmacist. Without the doctor's consent, never start, stop, or change the dosage of any medications. There has been no research on Penciclovir and drug interactions. Systemic medication interactions are uncommon since Penciclovir has a low systemic absorption rate.

Carcinogenesis, Mutagenesis, and Impairment of Fertility:

  • Carcinogenesis:

    • Famciclovir, the oral prodrug of Penciclovir, was tested for its carcinogenicity in two-year experiments on rats and mice. Based on the area under the plasma concentration curve comparisons [24-hour AUC (area under the curve)], the results showed that female rats receiving a dosage of 600 mg/kg/day (milligram per kilogram per day) which is roughly 395 times the maximum theoretical human exposure to Penciclovir through a topical application, exhibited the prevalence of mammary adenocarcinoma, a typical tumor in female rats, has increased for that particular strain. Male rats treated with doses up to 240 mg/kg/day (roughly 190 times the maximum theoretical human AUC for Penciclovir) and male and female mice treated with doses up to 600 mg/kg/day (roughly 100 times the maximum theoretical human AUC for Penciclovir) did not experience any appreciable increase in tumor incidence.

    • The fact that these studies were carried out on animals should not be overlooked. Additional study is needed to determine whether the results are applicable to human health and to develop suitable safety standards for the use of Famciclovir in people.

  • Mutagenesis: The positive results in the L5178Y mouse lymphoma cell test and human lymphocytes provide indications that Penciclovir may have clastogenic effects in specific cell lines and species. The rise in micronuclei seen in vivo for mouse bone marrow provides more evidence that Penciclovir may be genotoxic. To fully comprehend the consequences of these findings for human health and the safe use of Penciclovir, it is crucial to take these results into account in the context of the particular test systems employed and to carry out more research.

  • Fertility Impairment:

    • Penciclovir was given intravenously to rats and dogs repeatedly at high dosages (160 mg/kg/day for the rats and 100 mg/kg/day for the dogs), which caused testicular damage. The area under the plasma concentration curve (AUC) indicated that these dosages were roughly 1155 and 3255 times the maximum theoretical human exposure. The seminiferous tubules in both species' testicles atrophy, the number of sperm in the epididymis, and the frequency of aberrant sperm morphology or decreased motility were all observed alterations. Higher dosages or longer exposure times to Penciclovir were linked to the severity of these negative effects on the testes.

    • To completely understand the possible effects on human fertility and reproductive function, further study is required.

Dosage and Administration:

Each gram of Penciclovir cream contains 10 mg of Penciclovir, which is equivalent to a one percent (w/w) concentration in the cream base.

Supply, Storage, and Handling:

  • Supply - Penciclovir is a topical medicine and is available in two different packings (1.5 grams and five grams tubes). Each tube contains 10 milligrams of Penciclovir per gram.

  • Supply and Handling - Penciclovir is stored at 20 degrees Celsius to 25 degrees Celsius or 68 degrees Fahrenheit to 77 degrees Fahrenheit. It is transported between 59 degrees Fahrenheit and 86 degrees Fahrenheit.

What Are the Adverse Reactions of Penciclovir?

In clinical investigations, Penciclovir was well tolerated by individuals with herpes labialis. Site reactions at the place where the drug is applied, local anesthesia effect, and rash are frequent skin-related adverse effects associated with the use of Penciclovir. Also noted was taste alteration.

Clinical Trial Study and Drug Efficacy:

Adults with recurrent herpes labialis who were otherwise healthy were included in two double-blind, placebo-controlled studies to assess the effectiveness of Penciclovir. They were randomly allocated to Penciclovir and placebo. Subjects had to start their treatment within an hour of recognizing any indications of herpes labialis. They had to continue the treatment for four days and apply the study drug every two hours only while they were awake. The findings from the two trials showed that the average duration of the lesion and lesion pain was about a half-day shorter for Penciclovir when compared to placebo. In particular, the lesion pain and the lesion healing took around four and a half days for Penciclovir, whereas it was about five days for the placebo group. Thus, Penciclovir was found to be more effective than the placebo.

Source Article IclonSourcesSource Article Arrow
Dr. Pandian. P
Dr. Pandian. P

General Surgery


herpes simplex viruspenciclovir
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