Merck Manual

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Professional Version

Penciclovir and Famciclovir


Dawn Merton Boothe

, DVM, PhD, Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University

Last full review/revision Nov 2015 | Content last modified Nov 2015

Famciclovir is the prodrug form of penciclovir. Penciclovir is very similar to acyclovir in terms of mechanism of action and spectrum. Although it is much less potent than acyclovir, penciclovir accumulates to much higher concentrations inside the cell. Penciclovir has been studied in cats receiving famciclovir at 62.5 mg for 3 days; it appeared to be well tolerated.

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