What is "penciclovir"

n. A guanine analogue antiviral drug used (mostly topically) for the treatment of herpesvirus infections.

Penciclovir ( INN; ) 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.