Final answer:
Ganciclovir has a higher incidence of serious adverse reactions in immunocompromised patients compared to other antivirals like acyclovir, famciclovir, and valacyclovir used to treat herpes zoster.
Step-by-step explanation:
Among the antivirals used in treating herpes zoster, or shingles, ganciclovir has a higher incidence of serious adverse reactions in immunocompromised patients. Acyclovir, famciclovir, and valacyclovir are commonly used antivirals with mechanisms of action that include inhibiting nucleic acid biosynthesis, specifically targeting viral replication. These medications are generally preferred for their effectiveness and lower incidence of serious side effects; however, ganciclovir is reserved for cases that require it, such as with cytomegalovirus infections, because of its higher risk profile in individuals with compromised immune systems.