Over the past two decades, the treatment of these conditions has been transformed by guanosine nucleoside antivirals such as valacyclovir (Valtrex, a highly bioavailable prodrug of acyclovir (Zovirax, and famciclovir (Famvir), a highly bioavailable prodrug of penciclovir (Denavir).<br><b>OBJECTIVE</b>: We describe the pharmacology, pharmacokinetics, and clinical efficacy of valacyclovir for the treatment of herpes simplex, herpes zoster, and other viral infections.