Famciclovir is actually a "prodrug", which means that it does not directly fight against the virus. On the contrary, Famciclovir is transformed into Penciclovir in vivo, and Penciclovir is active to viruses. Famciclovir is active against the same virus as Aciclovir, but Famciclovir has a longer duration of action. This means that it is not necessary to take Aciclovir many times a day. Famciclovir cannot cure or prevent the spread of herpes infection. Famciclovir relieves pain, burning, itching, and symptoms associated with herpes infection.