Penciclovir is a
guanosine
Guanosine (symbol G or Guo) is a purine nucleoside comprising guanine attached to a ribose ( ribofuranose) ring via a β-N9- glycosidic bond. Guanosine can be phosphorylated to become guanosine monophosphate (GMP), cyclic guanosine monophosphate ...
analogue
antiviral drug used for the treatment of various
herpesvirus
''Herpesviridae'' is a large family of DNA viruses that cause infections and certain diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek word ''ἕρπειν ...
infections. It is a
nucleoside analogue
Nucleoside analogues are nucleosides which contain a nucleic acid analogue and a sugar. Nucleotide analogs are nucleotides which contain a nucleic acid analogue, a sugar, and a phosphate group with one to three phosphates.
Nucleoside and nucl ...
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
Famciclovir is a guanosine analogue antiviral drug used for the treatment of various herpesvirus infections, most commonly for herpes zoster (shingles). It is a prodrug form of penciclovir with improved oral bioavailability. Famciclovir is mark ...
is a
prodrug of penciclovir with improved oral bioavailability.
Penciclovir was approved for medical use in 1996.
Medical use
In
herpes labialis
Herpes labialis, commonly known as cold sores or fever blisters, is a type of infection by the herpes simplex virus that affects primarily the lip. Symptoms typically include a burning pain followed by small blisters or sores. The first attack ...
, 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 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
Aciclovir (ACV), also known as acyclovir, is an antiviral medication. It is primarily used for the treatment of herpes simplex virus infections, chickenpox, and shingles. Other uses include prevention of cytomegalovirus infections following tra ...
. 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
Nucleoside analogues are nucleosides which contain a nucleic acid analogue and a sugar. Nucleotide analogs are nucleotides which contain a nucleic acid analogue, a sugar, and a phosphate group with one to three phosphates.
Nucleoside and nucl ...
*
Famciclovir
Famciclovir is a guanosine analogue antiviral drug used for the treatment of various herpesvirus infections, most commonly for herpes zoster (shingles). It is a prodrug form of penciclovir with improved oral bioavailability. Famciclovir is mark ...
References
{{Antivirals
Anti-herpes virus drugs
Purines