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Systematic (IUPAC) name
Clinical data
Trade names Denavir
AHFS/ Monograph
MedlinePlus a697027
  • AU: B1
  • US: B (No risk in non-human studies)
Routes of
Legal status
Legal status
Pharmacokinetic data
Bioavailability 1.5% (oral), negligible (topical)
Protein binding <20%
Metabolism Viral thymidine kinase
Biological half-life 2.2–2.3 hours
Excretion Renal
CAS Number 39809-25-1 YesY
ATC code D06BB06 (WHO) J05AB13 (WHO)
PubChem CID 4725
DrugBank DB00299 YesY
ChemSpider 4563 YesY
KEGG D05407 YesY
Chemical data
Formula C10H15N5O3
Molar mass 253.258 g/mol

Penciclovir (INN; /ˌpɛnˈsklˌvɪər/[1]) is a guanosine analogue antiviral drug used for the treatment of various herpesvirus infections. It is a nucleoside analogue which exhibits low toxicity and good selectivity. Because penciclovir is absorbed poorly when given orally (by mouth) it is used more as a topical treatment, and is the active ingredient in the cold sore medications Denavir (NDC 0135-0315-52), Vectavir and Fenivir. Famciclovir is a prodrug of penciclovir with improved oral bioavailability.


In herpes labialis, the duration of healing, pain and detectable virus is reduced by up to one day,[2] compared with the total duration of 2–3 weeks of disease presentation.

Mode of action and selectivity[edit]

Penciclovir is inactive in its initial form. Within a virally infected cell a viral thymidine kinase adds a phosphate group to the penciclovir molecule; this is the rate-limiting step in the activation of penciclovir. Cellular (human) kinases then add two more phosphate groups, producing the active penciclovir triphosphate. This activated form inhibits viral DNA polymerase, thus impairing the ability of the virus to replicate within the cell.

The selectivity of penciclovir may be attributed to two factors. First, cellular thymidine kinases phosphorylate the parent form significantly less rapidly than does the viral thymidine kinase, so the active triphosphate is present at much higher concentrations in virally infected cells than in uninfected cells. Second, the activated drug binds to viral DNA polymerase with a much higher affinity than to human DNA polymerases. As a result, penciclovir exhibits negligible cytotoxicity to healthy cells.

The structure and mode of action of penciclovir are very similar to that of other nucleoside analogues, such as the more widely used aciclovir. A difference between aciclovir and penciclovir is that the active triphosphate form of penciclovir persists within the cell for a much longer time than the activated form of aciclovir, so the concentration within the cell of penciclovir will be higher given equivalent cellular doses.

See also[edit]


  1. ^ "Penciclovir". Merriam-Webster Dictionary. Retrieved 2016-01-22. 
  2. ^ Farmaceutiska Specialiteter i Sverige - the Swedish official drug catalog. [ --> Vectavir. Retrieved on August 12, 2009. Translated from "Tiden för läkning, smärta och påvisbart virus förkortas med upp till ett dygn."