Valtrex contains valaciclovir, an antiviral, which is the L-valine ester of aciclovir. Aciclovir is a purine (guanine) nucleoside analogue

Contains aciclovir, which is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against human herpes viruses, including herpes simplex virus (HSV) types I and II and varicella zoster virus (VZV)