Reactivation of VZV is known to occur in persons receiving immunosuppressive therapy. Which of the following is the best antiviral for treating this infection?

Acyclovir and its derivatives valacyclovir (d), famciclovir, and penciclovir all are effective in treating active herpes zoster (shingles). There is some evidence that valacyclovir and famciclovir are better in speeding cutaneous healing and resolving pain than acyclovir. Only acyclovir may be used in children. Amantadine (a) blocks the M2 channel of influenza A virus, although the vast majority of strains circulating currently are resistant; boceprevir (b) is an inhibitor of HCV NS3/4A protease; ribavirin (c) is used in the treatment of HCV and respiratory syncytial virus; and zidovudine (e) is a nucleoside reverse transcriptase inhibitor used in the treatment of HIV.