THE PHARMACOLOGICAL PROFILE OF FAMCICLOVIR

Famciclovir is the well-absorbed oral form of penciclovir, a potent an d selective antiviral agent, with activity against members of the herp esvirus family, including varicella-zoster virus (VZV), and herpes sim plex virus-1 (HSV-1) and HSV-2. Famciclovir is rapidly absorbed and co nverted to penciclovir. Penciclovir has excellent bioavailability (77% ) after oral administration of 500 mg of famciclovir. Similar to acycl ovir. famciclovir is converted by phosphorylation to its active metabo lite, penciclovir-triphosphate. Penciclovir-triphosphate has a prolong ed in vitro intracellular half-life of 10 to 20 hours in HSV-1- and HS V-2-infected cells, respectively, and 9 to 14 hours in VZV-infected ce lls. In contrast, the in vitro intracellular half-life of acyclovir is substantially shorter at 0.7 and 1 hours in HSV-1- and HSV-2-infected cells, respectively, and 0.8 hours in VZV-infected cells. Famciclovir is eliminated primarily via the kidneys. Dosage adjustment is not req uired for famciclovir in elderly patients with normal or mildly impair ed renal function, and the extent of penciclovir availability is not a ffected by food. The excellent bioavailability ensures that adequate d rug reaches virus-infected cells, and the prolonged intracellular half -life of the active form of famciclovir results in persistent antivira l activity. Copyright (C) 1996 by W.B. Saunders Company