Therapeutic substitute for valacyclovir:

Oseltamivir is an antiviral medication that is specifically used to treat and prevent influenza virus infections. It works by inhibiting a viral enzyme necessary for the replication of the influenza virus, making it ineffective for treating herpes viruses, which require a different class of antiviral drugs.

Baloxavir is an antiviral agent that targets influenza viruses by inhibiting the cap-dependent endonuclease involved in viral replication. Like oseltamivir, it is not effective against herpes viruses and therefore cannot serve as a substitute for valacyclovir in treating herpes-related conditions.

Ritonavir is primarily used as an antiretroviral medication for the treatment of HIV. It functions as a protease inhibitor, which is unrelated to the action of valacyclovir and famciclovir. Therefore, it is not suitable as a therapeutic alternative for viral infections treated by valacyclovir.