Within what time period is oral acyclovir most effective for herpes zoster eyelid findings?

Acyclovir, an antiviral medication, is most effective when initiated early in the course of herpes zoster (shingles) infection. For optimal outcomes, especially to mitigate complications like ocular involvement, treatment should ideally begin within 72 hours of the onset of the rash. This is because the antiviral effects significantly reduce viral replication during this critical window.

Starting treatment within this period helps in minimizing the severity and duration of symptoms, and it also lowers the risk of complications such as postherpetic neuralgia and potential vision loss when the eyelid is involved. Delaying treatment beyond this time frame can result in diminished efficacy, particularly in controlling the viral spread and associated inflammation. Thus, 72 hours post-onset is considered the maximum beneficial time frame for starting oral acyclovir in the context of herpes zoster with eyelid findings.