Acyclovir Dosing for Herpes Zoster (Shingles)
The recommended dosing of acyclovir for herpes zoster is 800 mg orally five times daily (every 4 hours) for 7 to 10 days. 1
Standard Dosing Regimens
Immunocompetent Adults
- First-line oral therapy:
- Acyclovir 800 mg orally 5 times daily for 7-10 days 1
- Treatment should be initiated as soon as possible, ideally within 72 hours of rash onset
Immunocompromised Patients
- For severe cases or immunocompromised patients:
- Intravenous acyclovir 5-10 mg/kg every 8 hours 2
- Consider switching to oral therapy once clinical improvement occurs
Pediatric Dosing
- Children under 45 kg:
- Children over 40 kg and adolescents:
- Adult dosing (800 mg 5 times daily) 2
Dosage Adjustments for Renal Impairment
Acyclovir requires dose adjustment in patients with renal impairment:
| Creatinine Clearance (mL/min) | 800 mg Oral Dose Adjustment |
|---|---|
| >25 | 800 mg every 4 hours, 5x daily |
| 10-25 | 800 mg every 8 hours |
| <10 | 800 mg every 12 hours |
For hemodialysis patients, an additional dose should be administered after each dialysis session 1.
Treatment Duration Considerations
- Standard treatment duration is 7 days for most patients 2
- Extended treatment (10 days) may be considered for:
- Severe cases
- Immunocompromised patients
- Patients with continued formation of new lesions
- Research has shown no significant benefit of extending treatment to 21 days compared to 7 days of therapy 4
Alternative Antiviral Options
While acyclovir is effective, alternative antivirals may offer advantages in terms of dosing convenience:
Valacyclovir (prodrug of acyclovir): 1000 mg three times daily for 7 days 2, 5
- Provides higher bioavailability than acyclovir
- Less frequent dosing (3 times daily vs. 5 times daily)
- Comparable efficacy to acyclovir with simpler dosing regimen 5
Famciclovir: 500 mg three times daily for 7 days 6
- Also offers less frequent dosing than acyclovir
Clinical Pearls and Pitfalls
- Timing is critical: Initiate treatment as soon as possible, ideally within 72 hours of rash onset for maximum effectiveness
- Hydration: Ensure adequate hydration during treatment to prevent crystalluria, especially with high-dose or IV therapy 2
- Monitoring: Watch for neurological symptoms (confusion, agitation, hallucinations) which may indicate neurotoxicity 2
- Treatment response: Evaluate response within 72 hours of initiating therapy; consider alternative approaches if no improvement
- Renal function: Check renal function before starting therapy, especially in elderly patients or those with known renal impairment
Special Considerations
- For ophthalmic zoster (involvement of the eye), consultation with an ophthalmologist is strongly recommended 3
- For disseminated zoster or CNS involvement, intravenous therapy is preferred
- Pain management should be addressed concurrently with antiviral therapy to improve quality of life
The evidence clearly supports the use of acyclovir 800 mg 5 times daily for 7-10 days as the standard dosing for herpes zoster, with appropriate adjustments for special populations and clinical scenarios.