What is the efficacy of antiviral agents in treating herpes zoster (shingles)?

Updated: Feb 11, 2021
  • Author: Camila K Janniger, MD; Chief Editor: Dirk M Elston, MD  more...
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Many studies have found acyclovir and its derivatives (valacyclovir, famciclovir, penciclovir, and desciclovir, which is not available in the United States) to be safe and effective in treating active disease and preventing PHN. Their mechanism of action involves preventing VZV replication through inhibition of viral DNA polymerase. [43, 100] Valacyclovir and famciclovir are not approved by the US Food and Drug Administration (FDA) for treatment of herpes zoster in children; acyclovir is more commonly used.

Antiviral therapy may decrease the length of time for new vesicle formation, the number of days to attain complete crusting, and the days of acute discomfort. Usually, the earlier antiviral medications are started, the more effective they are in shortening the duration of zoster and in preventing or decreasing the severity of PHN. Ideally, therapy should be initiated within 72 hours of symptom onset.

Controlled studies of antiviral use have only evaluated the efficacy of initiation of therapy within 48-72 hours of rash onset, demonstrating no loss of effectiveness when medications are started at any point during that period. [100] Several observational studies found antiviral therapy to be capable of reducing zoster pain even when started beyond the traditional 72-hour therapeutic window. [101, 102] Thus, antiviral therapy should be considered for acute zoster treatment regimens, regardless of the time of presentation.

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