|Trade names||Denavir, others|
|Drug class||Nucleoside analogue|
|Main uses||Herpes infection of the lip (cold sores)|
|Side effects||Irritation at the site of application|
|Bioavailability||1.5% (oral), negligible (topical)|
|Metabolism||Viral thymidine kinase|
|Elimination half-life||2.2–2.3 hours|
|Chemical and physical data|
|Molar mass||253.262 g·mol−1|
|3D model (JSmol)|
|Melting point||275 to 277 °C (527 to 531 °F)|
Penciclovir, sold under the brand name Denavir among others, is a medication used to treat herpes infection of the lip (cold sores). It reduces the time to healing from 8 to 7 days. It is applied to the area of infection.
Common side effects include irritation at the site of application. Use in pregnancy appears to be safe. It is a nucleoside analogue and is similar to acyclovir. Famciclovir is a precursor medication of penciclovir.
Penciclovir was approved for medical use in the United States in 1996. In the United States it costs about 800 USD for a 5 gram tube of cream as of 2021. It is more expensive than other equally useful medications.
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. 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.
Society and culture
It is the active ingredient in the cold sore medications Denavir (NDC 0135-0315-52), Vectavir and Fenivir.
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