NCIt definition : The sodium salt form of penciclovir, a synthetic acyclic guanine derivative with antiviral
activity, mainly used to treat infections from herpes simplex virus (HSV) types 1
and 2. In HSV infected cells, penciclovir is phosphorylated by viral thymidine kinase
and subsequently converted by cellular kinases into the active metabolite, penciclovir
triphosphate, which competitively inhibits viral HSV polymerase by blocking deoxyguanosine
triphosphate substrate binding. As a result, herpes viral DNA synthesis and replication
are selectively inhibited.;