What is the recommended dose of acyclovir (antiviral medication) for a shingles outbreak?

Acyclovir Dosing for Shingles (Herpes Zoster)

For acute shingles outbreaks, the standard dose is acyclovir 800 mg orally five times daily for 7 days, which should be initiated within 72 hours of rash onset for maximum benefit. 1

Standard Treatment Regimen

• Acyclovir 800 mg orally five times daily (every 4 hours while awake) for 7-10 days is the FDA-approved and guideline-recommended dose for acute herpes zoster 1, 2
• Treatment must be started within 72 hours of rash onset to achieve meaningful clinical benefit 3
• Starting therapy after 48 hours significantly reduces effectiveness in preventing complications 3

Clinical Benefits of Treatment

When initiated early, acyclovir at this dose provides:

• Faster resolution of new lesion formation and accelerated crusting 3
• Reduction in acute pain during the treatment phase 4, 3
• Decreased viral shedding 5
• Prevention of dissemination and visceral complications, particularly in immunocompromised patients 5

Important Dosing Considerations

Duration of Therapy

• 7 days is the standard duration for immunocompetent patients 1, 4
• Extending treatment to 21 days offers no significant additional benefit over 7 days and does not reduce postherpetic neuralgia 4
• For severe disease requiring hospitalization, consider 7-10 days of therapy 1

Immunocompromised Patients

• Intravenous acyclovir 5-10 mg/kg every 8 hours is recommended for severe disease or complications 2, 5
• Higher doses and longer duration may be necessary in HIV-infected or otherwise immunosuppressed patients 2

Renal Impairment

Critical dosing adjustments are required based on creatinine clearance 1:

• CrCl >25 mL/min: 800 mg every 4 hours (5 times daily) - standard dose
• CrCl 10-25 mL/min: 800 mg every 8 hours
• CrCl 0-10 mL/min: 800 mg every 12 hours
• Hemodialysis patients: Administer an additional dose after each dialysis session 1

Critical Pitfalls to Avoid

• Do not delay treatment waiting for laboratory confirmation - clinical diagnosis is sufficient and early initiation is paramount 3
• Ensure adequate hydration during therapy, as acyclovir requires good urine flow to prevent crystalluria at these high doses 5
• Monitor mental status in elderly patients, as acyclovir can rarely cause neurologic side effects 5
• Do not use topical acyclovir - it is substantially less effective than oral therapy 2

Alternative Agents with Superior Convenience

While acyclovir remains effective, newer antivirals offer simpler dosing:

• Valacyclovir 1000 mg three times daily for 7 days provides equivalent or superior efficacy with better bioavailability and significantly reduces duration of postherpetic neuralgia (median 38 days vs 51 days with acyclovir) 6
• Famciclovir 500 mg three times daily for 7 days is comparable to acyclovir for acute parameters and reduces median duration of postherpetic neuralgia by 3.5 months in patients ≥50 years 7

Postherpetic Neuralgia Prevention

• Neither 7-day nor 21-day acyclovir regimens have been definitively proven to prevent postherpetic neuralgia 4, 3
• Valacyclovir and famciclovir demonstrate superior reduction in postherpetic neuralgia duration compared to acyclovir 6, 7
• Adding corticosteroids (prednisolone 40 mg daily, tapered over 3 weeks) to acyclovir provides only slight benefit in acute pain reduction but does not prevent postherpetic neuralgia and increases adverse events 4