Penciclovir is a
guanosine analogue
antiviral drug
Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do n ...
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 more often used as a topical treatment. It is the active ingredient in the cold sore medications Denavir (
NDC 0135-0315-52), Vectavir and Fenivir.
Famciclovir is a
prodrug
A prodrug is a medication or compound that, after intake, is metabolized (i.e., converted within the body) into a pharmacologically active drug. Instead of administering a drug directly, a corresponding prodrug can be used to improve how the drug ...
of penciclovir with improved oral bioavailability.
Penciclovir was approved for medical use in 1996.
Medical use
In
herpes labialis, the duration of healing, pain and detectable virus is reduced by up to one day,
[Farmaceutiska Specialiteter i Sverige - the Swedish official drug catalog. [http://www.fass.se Fass.se]
--> Vectavir. Retrieved on August 12, 2009. Translated from "Tiden för läkning, smärta och påvisbart virus förkortas med upp till ett dygn." compared with the total duration of 2–3 weeks of disease presentation.
Mechanism of action
Penciclovir is inactive in its initial form. Within a virally infected cell a viral thymidine kinase">Fass.se">Farmaceutiska Specialiteter i Sverige - the Swedish official drug catalog
compared with the total duration of 2–3 weeks of disease presentation.
Mechanism of action
Penciclovir is inactive in its initial form. Within a virally infected cell a viral thymidine kinase adds a phosphate">Fass.se
--> Vectavir. Retrieved on August 12, 2009. Translated from "Tiden för läkning, smärta och påvisbart virus förkortas med upp till ett dygn." compared with the total duration of 2–3 weeks of disease presentation.
Mechanism of action
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
Selectivity may refer to:
Psychology and behaviour
* Choice, making a selection among options
* Discrimination, the ability to recognize differences
* Socioemotional selectivity theory, in social psychology
Engineering
* Selectivity (radio), a ...
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
Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are an immune cell or some types of venom, e.g. from the puff adder (''Bitis arietans'') or brown recluse spider (''Loxosceles reclusa'').
Cell physiology
Treating cells ...
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
*
Nucleoside analogue
*
Famciclovir
References
{{Antivirals
Anti-herpes virus drugs
Purines