About Famciclovir Nucleosides and Nucleotides :A synthetic acyclic guanine analogue , Antiviral for HSV, Varicella-Zoster. Mechanism of Action of Famciclovir Famciclovir is a prodrug and it is converted to active Penciclovir. It undergoes phosphorylation in the presence Thymidine kinase and form Penciclovir monophosphate and it is again phosphorylated by Cellular kinase and form Penciclovir triphosphate. This Penciclovir triphosphate inhibits DNA polymerase enzyme and inhibits DNA synthesis and consequently inhibit viral replication. Indications for Famciclovir 1.Herpes simplex virus infection 2.Herpes zoster and genital herpes infections in immunocompromised patients Interactions for Famciclovir Uricosurics: probenicid possibly reduces famciclovir excretion thereby increasing plasma concentration.