Complex sentence: 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.
Split into simpler sentences: 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.