Duration of Acyclovir Treatment for Herpes Zoster
For immunocompetent adults with herpes zoster, treat with acyclovir 800 mg orally five times daily for 7 days, starting within 72 hours of rash onset for maximum benefit. 1, 2
Standard Treatment Duration and Dosing
- The recommended duration is 7 days for uncomplicated herpes zoster in immunocompetent patients 1, 3, 4
- The standard dose is acyclovir 800 mg orally five times daily 1, 2, 3
- Treatment should ideally be initiated within 72 hours of rash onset, with greatest efficacy when started within 48 hours 1, 3
Evidence Supporting 7-Day Duration
The 7-day regimen is supported by multiple high-quality trials demonstrating that it effectively shortens time to lesion scabbing, healing, and cessation of pain 3, 4. A landmark randomized controlled trial directly comparing 7 days versus 21 days of acyclovir found no significant difference in postherpetic neuralgia prevention between the two durations, with the 21-day course offering only slight additional benefits in acute pain reduction that did not justify the extended treatment 4.
Extended Duration Scenarios
For severe or complicated disease, extend treatment to 7-10 days or until clinical resolution is attained:
- Disseminated or multi-dermatomal herpes zoster requires intravenous acyclovir 5-10 mg/kg every 8 hours for 7-10 days, then switch to oral therapy once clinical improvement occurs 1, 5
- Immunocompromised patients may require longer treatment courses if healing is delayed or new lesions continue to form beyond 7 days 1
- Ophthalmic zoster or visceral involvement warrants extended treatment until complete clinical resolution 1
Critical Timing Considerations
- Delayed initiation beyond 72 hours significantly reduces treatment effectiveness 1, 3
- Patients treated after 48 hours showed no significant hastening of rash healing in controlled trials 3
- However, immunocompromised patients require antiviral treatment regardless of timing of presentation 1
Common Pitfalls to Avoid
- Do not extend routine treatment beyond 7 days in immunocompetent patients, as the 21-day regimen provides no meaningful reduction in postherpetic neuralgia 4
- Do not use the lower 400 mg five times daily dose, as it has not shown significant benefit compared to placebo 6
- Do not continue treatment indefinitely—acyclovir does not eradicate latent virus or prevent future recurrences 5
- Monitor for treatment failure in immunocompromised patients, as acyclovir-resistant strains may require foscarnet 40 mg/kg IV every 8 hours 1