Acyclovir Dosing for Shingles (Herpes Zoster)
For uncomplicated herpes zoster (shingles), the recommended dose of oral acyclovir is 800 mg five times daily for 7 days. 1, 2
Dosing Details
- Standard regimen: 800 mg orally every 4 hours (while awake), 5 times daily for 7 days
- Treatment should be initiated within 72 hours of rash onset for maximum effectiveness 1
- Treatment should continue until all lesions have scabbed 1
Dosage Adjustments for Renal Impairment
Acyclovir requires dose adjustment in patients with renal impairment:
| Creatinine Clearance (mL/min) | Dose Adjustment for 800 mg |
|---|---|
| >25 | 800 mg every 4 hours, 5 times daily |
| 10-25 | 800 mg every 8 hours |
| 0-10 | 800 mg every 12 hours |
For hemodialysis patients, an additional dose should be administered after each dialysis session 2.
Special Considerations
- Timing matters: Treatment is most effective when started within 48 hours of rash onset. Starting treatment later than 48 hours after rash onset significantly reduces the benefits of therapy 3
- Intravenous option: For severe cases, intravenous acyclovir (5-10 mg/kg every 8 hours for 5-7 days) may be considered 1
- Immunocompromised patients: May require longer treatment duration and closer monitoring 1
- Alternative antivirals: Valacyclovir (1000 mg three times daily for 7 days) or famciclovir (500 mg three times daily for 7 days) are alternatives with simpler dosing schedules 1
Clinical Pearls
- Acyclovir significantly reduces the time to last new lesion formation, loss of vesicles, and full crusting of lesions 3
- While acyclovir effectively treats acute symptoms, its effect on preventing postherpetic neuralgia (PHN) is less established 4, 3
- Newer antivirals like valacyclovir and famciclovir offer simpler dosing schedules (3 times daily vs. 5 times daily for acyclovir) with comparable efficacy for cutaneous healing 5, 6
- Famciclovir has been shown to reduce the duration of postherpetic neuralgia when administered during acute infection 7
Common Pitfalls to Avoid
- Delayed initiation: Starting treatment beyond 72 hours after rash onset significantly reduces effectiveness
- Inadequate dosing: The full dose of 800 mg five times daily is necessary for optimal outcomes
- Premature discontinuation: Treatment should continue for the full 7 days even if symptoms improve
- Failure to adjust for renal function: Acyclovir can accumulate in patients with renal impairment, potentially leading to neurotoxicity if not properly adjusted